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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Plant Sci.</journal-id>
<journal-title>Frontiers in Plant Science</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Plant Sci.</abbrev-journal-title>
<issn pub-type="epub">1664-462X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fpls.2022.854171</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Plant Science</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Genome-Wide Identification and Characterization of TCP Family Genes in Pak-Choi [<italic>Brassica campestris</italic> (syn. <italic>Brassica rapa</italic>) ssp. <italic>chinensis</italic> var. <italic>communis</italic>]</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name><surname>Huang</surname> <given-names>Feiyi</given-names></name>
<xref ref-type="author-notes" rid="fn002"><sup>&#x2020;</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Shi</surname> <given-names>Churan</given-names></name>
<xref ref-type="author-notes" rid="fn002"><sup>&#x2020;</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Zhang</surname> <given-names>Yuhang</given-names></name>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Hou</surname> <given-names>Xilin</given-names></name>
<xref ref-type="corresp" rid="c001"><sup>&#x002A;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/251121/overview"/>
</contrib>
</contrib-group>
<aff><institution>State Key Laboratory of Crop Genetics &#x0026; Germplasm Enhancement, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (East China), Ministry of Agriculture and Rural Affairs of the P. R. China, Engineering Research Center of Germplasm Enhancement and Utilization of Horticultural Crops, Ministry of Education of the P. R. China, Nanjing Suman Plasma Engineering Research Institute, Nanjing Agricultural University</institution>, <addr-line>Nanjing</addr-line>, <country>China</country></aff>
<author-notes>
<fn fn-type="edited-by"><p>Edited by: Mukesh Jain, Jawaharlal Nehru University, India</p></fn>
<fn fn-type="edited-by"><p>Reviewed by: Xiao-Li Tan, Jiangsu University, China; Jianjun Zhao, Agricultural University of Hebei, China</p></fn>
<corresp id="c001">&#x002A;Correspondence: Xilin Hou, <email>hxl@njau.edu.cn</email></corresp>
<fn fn-type="equal" id="fn002"><p><sup>&#x2020;</sup>These authors have contributed equally to this work</p></fn>
<fn fn-type="other" id="fn004"><p>This article was submitted to Plant Abiotic Stress, a section of the journal Frontiers in Plant Science</p></fn>
</author-notes>
<pub-date pub-type="epub">
<day>09</day>
<month>05</month>
<year>2022</year>
</pub-date>
<pub-date pub-type="collection">
<year>2022</year>
</pub-date>
<volume>13</volume>
<elocation-id>854171</elocation-id>
<history>
<date date-type="received">
<day>13</day>
<month>01</month>
<year>2022</year>
</date>
<date date-type="accepted">
<day>17</day>
<month>03</month>
<year>2022</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#x00A9; 2022 Huang, Shi, Zhang and Hou.</copyright-statement>
<copyright-year>2022</copyright-year>
<copyright-holder>Huang, Shi, Zhang and Hou</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/"><p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p></license>
</permissions>
<abstract>
<p>The TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) gene family, a kind of plant specific transcription factor, is essential for stress response, cell growth, and cell proliferation. However, the characterization of TCP family is still not clear in Pak-choi [<italic>Brassica campestris</italic> (syn. <italic>Brassica rapa</italic>) ssp. <italic>chinensis</italic> var. <italic>communis</italic>]. In this study, genome-wide analysis of TCP gene family was performed and 26 <italic>TCP</italic> genes were identified in Pak-choi. Phylogenetic analysis demonstrated that the 26 BcTCPs were divided into two classes: Class I and Class II. Class II was further classified into two subclasses, CIN and CYC/TB1. The qPCR results suggested that most <italic>BcTCPs</italic> respond to abiotic stresses. The expressions of <italic>BcTCP3</italic>, <italic>BcTCP12</italic>, <italic>BcTCP21</italic>, and <italic>BcTCP22</italic> were significantly changed under ABA and cold treatment. <italic>BcTCP3</italic> and <italic>BcTCP12</italic> were also up-regulated under osmotic treatment. Subcellular localization showed that BcTCP3 and BcTCP21 were located in the nucleus. Our results will facilitate revealing the functions and regulatory mechanisms of <italic>BcTCPs</italic>.</p>
</abstract>
<kwd-group>
<kwd>abiotic stress</kwd>
<kwd>expression analysis</kwd>
<kwd>subcellular localization</kwd>
<kwd>TCP</kwd>
<kwd>Pak-choi</kwd>
</kwd-group>
<counts>
<fig-count count="4"/>
<table-count count="0"/>
<equation-count count="0"/>
<ref-count count="42"/>
<page-count count="8"/>
<word-count count="4675"/>
</counts>
</article-meta>
</front>
<body>
<sec id="S1" sec-type="intro">
<title>Introduction</title>
<p>The TCP gene family is a class of plant-specific transcription factors and plays important roles in plant growth and development. TCP was named from four genes members: <italic>TEOSINTE BRANCHED 1</italic> (<italic>TB1</italic>) from maize (<italic>Zea mays</italic>) (<xref ref-type="bibr" rid="B5">Doebley et al., 1995</xref>), <italic>CYCLOIDEA</italic> (<italic>CYC</italic>) from snapdragon (<italic>Antirrhinum majus</italic>) (<xref ref-type="bibr" rid="B21">Luo et al., 1996</xref>), and the <italic>PROLIFERATING CELL FACTORS 1</italic> (<italic>PCF1</italic>) and <italic>PCF2</italic> from rice (<italic>Oryza sativa</italic>) (<xref ref-type="bibr" rid="B14">Kosugi and Ohashi, 1997</xref>). <italic>TB1</italic> is a key factor to control apical dominance in maize (<xref ref-type="bibr" rid="B6">Doebley et al., 1997</xref>). <italic>CYC</italic> involves in the regulation of floral asymmetry in snapdragons. PCF1 and PCF2 bind to the promoter of <italic>PROLIFERATING CELL NUCLEAR ANTIGEN</italic> (<italic>PCNA</italic>) gene in rice, which involves in DNA replication and repair, maintenance of chromatin structure, chromosome segregation, and cell-cycle progression (<xref ref-type="bibr" rid="B21">Luo et al., 1996</xref>; <xref ref-type="bibr" rid="B14">Kosugi and Ohashi, 1997</xref>). TCP proteins contain a 59-amino-acid domain with a bHLH motif that involved in DNA binding and protein-protein interaction (<xref ref-type="bibr" rid="B23">Martin-Trillo and Cubas, 2010</xref>). According to the conserved domain, TCP proteins can be divided into two classes: Class I (TCP-P Class) and Class II (TCP-C Class) (<xref ref-type="bibr" rid="B15">Kosugi and Ohashi, 2002</xref>; <xref ref-type="bibr" rid="B26">Navaud et al., 2007</xref>). Class II can be further divided into two subclades: CIN and CYC/TB1 (<xref ref-type="bibr" rid="B23">Martin-Trillo and Cubas, 2010</xref>). Class I includes <italic>PCF1</italic> and <italic>PCF2</italic> in rice, <italic>TCP8</italic>, <italic>TCP9</italic>, <italic>TCP14</italic>, <italic>TCP20</italic>, etc. in <italic>Arabidopsis</italic>. Class II contains <italic>TB1</italic> in maize, <italic>TCP1</italic>, <italic>TCP2</italic>, <italic>TCP4</italic>, <italic>TCP10</italic>, <italic>BCR1</italic>, <italic>BCR2</italic>, etc. in <italic>Arabidopsis</italic>.</p>
<p>Abiotic stress has an important effect on plant growth and productivity. Cold stress slows down the metabolic processes of plants, inhibits auxin transport and root elongation (<xref ref-type="bibr" rid="B31">Shibasaki et al., 2009</xref>). Salt stress leads to the accumulation of toxic ions in cells, which influences plant absorption of nutrients and water (<xref ref-type="bibr" rid="B3">Boudsocq and Lauri&#x00E8;re, 2005</xref>). Plants are subjected to dehydration under low temperature, high salinity, and drought environmental conditions, of which cause osmotic stress, inducing Abscisic acid (ABA) biosynthesis. ABA functions in multiple stresses, regulating genes related to dehydration and cold stress and controlling osmotic stress tolerance (<xref ref-type="bibr" rid="B39">Yamaguchi-Shinozaki and Shinozaki, 2006</xref>; <xref ref-type="bibr" rid="B9">Fujita et al., 2011</xref>). Moreover, ABA can reduce water loss by governing stomatal closure (<xref ref-type="bibr" rid="B13">Kim et al., 2010</xref>). The growth and development of plants will be severely affected when plants suffer from abiotic stresses. Hence, the study of response mechanisms during abiotic stresses is vital for species. At present, it is reported that many genes of the TCP family are related to various stresses. TCP20 responds to nitrate availability by interacting with NIN-like protein 6 (NLP6) and NLP9, controlling plants root growth (<xref ref-type="bibr" rid="B10">Guan et al., 2017</xref>). <italic>OsTCP19</italic> is up-regulated under drought, salt, and cold stress, indicating <italic>OsTCP19</italic> may involve in the stress tolerance (<xref ref-type="bibr" rid="B25">Mukhopadhyay and Tyagi, 2015</xref>). In <italic>Cicer arietinum</italic>, five TCP genes (<italic>CaTCP3</italic>/<italic>13</italic>/<italic>15</italic>/<italic>20</italic>/<italic>21</italic>), which contained the MYB <italic>cis</italic>-elements, were strongly induced under drought conditions, and similar results were found in other legumes (<xref ref-type="bibr" rid="B17">Ling et al., 2020</xref>). <italic>Oryza sativa miR319</italic> (<italic>Osa-miR319</italic>), an upstream gene of <italic>OsPCF5</italic>, <italic>OsPCF6</italic>, <italic>OsPCF8</italic>, and <italic>OsTCP21</italic>, is decreased in the cold condition in rice. Meanwhile, overexpressing <italic>Osa-miR319</italic> results in down-regulation of its downstream target genes and enhances cold resistance, impling that TCP21 could involve in cold stress (<xref ref-type="bibr" rid="B40">Yang et al., 2013</xref>; <xref ref-type="bibr" rid="B34">Wang et al., 2014</xref>). In creeping bentgrass (<italic>Agrostis stolonifera</italic>), overexpressing <italic>Osa-miR319</italic> also reduces the expression of its target genes (<italic>AsPCF5</italic>, <italic>AsPCF6</italic>, <italic>AsPCF8</italic>, and <italic>AsTCP14</italic>), enhancing salt and drought tolerance (<xref ref-type="bibr" rid="B42">Zhou et al., 2013</xref>). GmTCP8 interacts with GmPYL10 and involves in the ABA signal pathway in soybean (<xref ref-type="bibr" rid="B8">Feng et al., 2018</xref>). <italic>ZmTCP42</italic> is associated with ABA and drought stress, which plays an active role in drought tolerance (<xref ref-type="bibr" rid="B4">Ding et al., 2019</xref>). AtTCP14 represses <italic>ABA1</italic> (<italic>ABA DEFICIENT 1</italic>) and other ABA-related stress genes in <italic>Arabidopsis</italic> seeds (<xref ref-type="bibr" rid="B30">Rueda-Romero et al., 2012</xref>).</p>
<p>Until now, the study of the TCP family has been more and more comprehensive, which have been identified in many species including <italic>Arabidopsis thaliana</italic> (<xref ref-type="bibr" rid="B16">Li, 2015</xref>), rice (<italic>Oryza sativa</italic>) (<xref ref-type="bibr" rid="B41">Yao et al., 2007</xref>), turnips (<italic>Brassica rapa</italic> ssp. <italic>rapa</italic>) (<xref ref-type="bibr" rid="B7">Du et al., 2017</xref>), poplar (<italic>Populus trichocarpa</italic>) (<xref ref-type="bibr" rid="B22">Ma et al., 2016</xref>), tomato (<italic>Solanum lycopersicum</italic>) (<xref ref-type="bibr" rid="B28">Parapunova et al., 2014</xref>), Switchgrass (<italic>Panicum virgatum</italic> L.) (<xref ref-type="bibr" rid="B12">Huo et al., 2019</xref>), <italic>Brassica rapa</italic> and <italic>Brassica oleracea</italic> (<xref ref-type="bibr" rid="B19">Liu et al., 2019</xref>). Pak-choi [<italic>Brassica campestris</italic> (syn. <italic>Brassica rapa</italic>) ssp. <italic>chinensis</italic> var. <italic>communis</italic>] has gradually become worldwide vegetable crops. However, Pak-choi <italic>TCP</italic> genes and their regulatory mechanisms are still not clear.</p>
<p>In this study, genome-wide analysis of TCP family genes in Pak-choi was performed. 26 <italic>BcTCP</italic> genes were identified in Pak-choi. Phylogenetic relationship, subcellular localization, and conserved motifs were analyzed. QPCR was employed to illustrate the expression patterns of <italic>BcTCPs</italic> under salt, osmotic, cold, and ABA treatment. The results showed that <italic>BcTCPs</italic> may involve in multiple abiotic stresses. Our findings provide a theoretical basis for further research on the potential functions and regulatory mechanisms of <italic>BcTCP</italic> genes.</p>
</sec>
<sec id="S2" sec-type="materials|methods">
<title>Materials and Methods</title>
<sec id="S2.SS1">
<title>Cloning and Identification of <italic>BcTCP</italic> Gene Family Members</title>
<p>Total RNA was extracted from Pak-choi using the RNAeasy Mini Kit (Tiangen, Beijing, China). The CDSs of the <italic>BcTCPs</italic> were amplified with gene specific primers based on the sequences of <italic>AtTCPs</italic> by homology cloning (<xref ref-type="bibr" rid="B11">Huang et al., 2019</xref> and <xref ref-type="supplementary-material" rid="TS1">Supplementary Table 1</xref>). The PCR products were cloned into the pMD18-T vector before sequencing. Then, the obtained plasmids were sequenced by TSINGKE (Nanjing, China). All putative BcTCP proteins sequences were analyzed using the Pfam database<sup><xref ref-type="fn" rid="footnote1">1</xref></sup>. Additionally, protein molecular weight, isoelectric point, and amino acid length of BcTCPs were computed by the ExPASy ProtParam tool<sup><xref ref-type="fn" rid="footnote2">2</xref></sup>.</p>
</sec>
<sec id="S2.SS2">
<title>Phylogenetic Tree and <italic>Cis</italic>-Acting Elements Analysis</title>
<p>24 <italic>AtTCP</italic> genes were retrieved from TAIR<sup><xref ref-type="fn" rid="footnote3">3</xref></sup>. Multiple sequence alignments of putative BcTCPs and AtTCPs were performed using Clustal X 2.1. Phylogenetic tree was completed by the Maximum Likelihood (ML) method using MEGA 7.0 software. The bootstrap values were performed with 1,000 replications. PlantCARE<sup><xref ref-type="fn" rid="footnote4">4</xref></sup> was used to analyze <italic>cis</italic>-acting elements in promoters of each <italic>BcTCP</italic> gene. After classifying and counting the elements on each promoter (<xref ref-type="supplementary-material" rid="TS2">Supplementary Table 2</xref>), the heat map was made by TBtools.</p>
</sec>
<sec id="S2.SS3">
<title>Conserved Domain Analysis</title>
<p>The conserved motifs were analyzed using MEME program<sup><xref ref-type="fn" rid="footnote5">5</xref></sup> with the default settings except the maximum width was set to 200, and the minimum and maximum numbers of motifs were defifined as 2 and 10, respectively.</p>
</sec>
<sec id="S2.SS4">
<title>Plant Materials and Growth Conditions</title>
<p>The Pak-choi cultivar &#x2018;49caixin&#x2019; was selected in our experiment, which has a short life cycle and may flower within two months after sowing under long-day conditions (<xref ref-type="bibr" rid="B33">Tian et al., 2004</xref>). Plants were cultivated in pots with medium (Soil matrix and vermiculite, 1:1). All seedlings were grown in a controlled artificial climatic chamber under the same conditions (16 h light at 22&#x00B0;C/8 h dark at 18&#x00B0;C, 60-70% relative humidity). One-month-old seedlings were treated with 100 &#x03BC;M ABA, 250 mM NaCl and 20% PEG6000, respectively. For cold treatment, one-month-old seedlings were transferred to 4&#x00B0;C. The leaves were collected under each stress treatment in a continuous time course (0, 10, 20, 30, 40, 50 min, 1, 2, 3, 4, 8 h) and stored at &#x2212;70&#x00B0;C immediately for RNA extraction.</p>
</sec>
<sec id="S2.SS5">
<title>Expression Analysis of <italic>BcTCP</italic> Genes by qPCR</title>
<p>Following the manufacturer&#x2019;s instructions, total RNA was isolated from leaves using the RNA easy mini kit (Tiangen, Beijing, China). Then first-strand cDNA was synthesized with a RevertAid First Strand cDNA Synthesis Kit (Thermo, Shanghai, China). Primers for qPCR were designed using Primer 5.0 (<xref ref-type="supplementary-material" rid="TS1">Supplementary Table 1</xref>). QPCR was performed using the SYBR<sup>&#x00AE;</sup> Premix Ex Taq kit (Takara, Dalian, China). <italic>BcActin</italic> was used as an internal reference gene. Results were calculated by the 2<sup>&#x2013;&#x0394;&#x0394;CT</sup> method (<xref ref-type="bibr" rid="B20">Livak and Schmittgen, 2001</xref>).</p>
</sec>
<sec id="S2.SS6">
<title>Subcellular Localization Analysis</title>
<p>WOLF PSORT<sup><xref ref-type="fn" rid="footnote6">6</xref></sup> was used to predict the subcellular localization of the putative BcTCP proteins. To further confirm their subcellular localization, the protein-coding regions of <italic>BcTCP3</italic> and <italic>21</italic> without the termination codon were amplified and then cloned into pCambia 1,302 vector in fusion with GFP at C-terminal end (<italic>35S: GFP</italic>), generating the fusion constructs. The <italic>35S: BcTCP3-GFP</italic> and <italic>35S: BcTCP21-GFP</italic> were generated. Each plasmid was injected into the tobacco leaves by <italic>Agrobacterium tumefaciens</italic>-mediated transient transformation (strain GV3101). The tobacco was incubated for 12 h under darkness. 2-3 days after injection, the fluorescence of GFP was observed and photographed by confocal microscopy (Leica, TCS SP2, Wetzlar, Germany). DAPI (nucleus specific dye) was used as nuclei dye in the experiment.</p>
</sec>
</sec>
<sec id="S3" sec-type="results">
<title>Results</title>
<sec id="S3.SS1">
<title>Identification of <italic>TCP</italic>s in Pak-Choi</title>
<p>A total of 26 <italic>TCP</italic> genes in Pak-choi were obtained by homology cloning based on the <italic>Arabidopsis thaliana TCP</italic> genes. These 26 genes were named <italic>BcTCP1</italic>&#x223C;<italic>BcTCP26</italic>. The CDS length of the 26 <italic>BcTCP</italic>s was ranged from 651 to 1,395 bp. The physical and chemical properties were further analyzed using the ExPASy ProtParam tool. The molecular weight of 26 putative BcTCP proteins varied from 23.12 to 56.74 kDa. The isoelectric point was ranged from 5.49 to 9.99, and the amino acid length was ranged from 216 to 520 aa (<xref ref-type="supplementary-material" rid="TS3">Supplementary Table 3</xref>).</p>
</sec>
<sec id="S3.SS2">
<title>Phylogenetic Analysis</title>
<p>An unrooted phylogenetic tree was constructed with the Maximum Likelihood (ML) method (<xref ref-type="fig" rid="F1">Figure 1</xref>). 26 <italic>BcTCPs</italic> were divided into two classes, Class I and Class II. The Class II <italic>TCP</italic>s were further categorized into two subgroups, CIN and CYC/TB1. PCF Class (Class I) contained 13 genes, CYC/TB1 Class contained 7 genes, CIN only contained 6 genes. Sequence analysis showed that <italic>AtTCP3</italic>, <italic>6</italic>, <italic>11</italic>, <italic>13</italic>, <italic>16</italic>, <italic>17</italic>, <italic>20</italic>, <italic>23</italic> had no ortholog in Pak-choi. <italic>AtTCP1</italic>, <italic>7</italic>, <italic>15</italic>, <italic>18</italic>, <italic>21</italic>, and <italic>24</italic> had more than one ortholog in the Pak-choi.</p>
<fig id="F1" position="float">
<label>FIGURE 1</label>
<caption><p>The phylogenetic tree and conserved motifs of BcTCP and AtTCP proteins. Each motif represented with a specific color was shown.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fpls-13-854171-g001.tif"/>
</fig>
</sec>
<sec id="S3.SS3">
<title>Conserved Domain Analysis</title>
<p>The conserved motifs of BcTCP proteins were analyzed using MEME. A total of 7 motifs were found in BcTCPs. The motifs were more similar in the same class. Furthermore, similar conserved motifs arrangements can be observed in the same clade. Motif 1 was conserved in all BcTCPs. Motif 3 and motif 6 only existed in Class II except for BcTCP5, 6, 11, and 13 (<xref ref-type="fig" rid="F1">Figure 1</xref>), suggesting that these BcTCPs may have similar functions. However, proteins among different groups shared diverse motifs. Motif 2 is presented in Class I (PCF) except for BcTCP20. Motif 7 was only existed in BcTCP15, 16, and 17. Motif 4 and motif 5 both existed in BcTCP7, BcTCP8, BcTCP21, BcTCP22, and BcTCP23. These results indicated that TCP genes may perform different functions in Pak-choi.</p>
</sec>
<sec id="S3.SS4">
<title>Analysis of <italic>Cis</italic>-Acting Elements in <italic>BcTCPs</italic> Promoters</title>
<p><italic>Cis</italic>-acting elements existed in gene promoters can affect gene expressions and functions. In this study, we found that <italic>BcTCPs</italic> promoters contained not only basic core elements, like TATA-box and CAAT-box, but also a variety of <italic>cis</italic>-acting elements, such as light response elements, hormone response elements, environment response elements, development response elements, and other functional elements (<xref ref-type="fig" rid="F2">Figure 2</xref>). All Class II <italic>BcTCPs</italic> promoters contained G-box elements and ABRE elements except for <italic>BcTCP20</italic> and <italic>BcTCP21</italic>. In Class I <italic>BcTCPs</italic>, the promoters of <italic>BcTCP2</italic>, <italic>3</italic>, <italic>11</italic>, <italic>12</italic>, <italic>13</italic>, <italic>25</italic>, and <italic>26</italic> all contained the low temperature response element (LTR). AT&#x223C;TATA box1 was identified in most all <italic>BcTCP</italic> promoters except <italic>BcTCP6</italic> and <italic>BcTCP23</italic>. The promoters of <italic>BcTCP2</italic>, <italic>3</italic>, <italic>4</italic>, <italic>10</italic>, <italic>11</italic>, <italic>12</italic>, <italic>14</italic>, <italic>15</italic>, <italic>20</italic>, <italic>21</italic>, <italic>22</italic>, <italic>26</italic> contained MYB, MYC, and MYB-like sequence elements at the same time. As a result, we hypothesized that these <italic>BcTCP</italic> genes may be involved in stress (<xref ref-type="bibr" rid="B1">Abe et al., 2003</xref>; <xref ref-type="bibr" rid="B38">Xu et al., 2021</xref>).</p>
<fig id="F2" position="float">
<label>FIGURE 2</label>
<caption><p><italic>Cis</italic>-acting elements on promoters of <italic>BcTCP</italic> genes. The color bar showed the number of <italic>cis</italic>-acting elements.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fpls-13-854171-g002.tif"/>
</fig>
</sec>
<sec id="S3.SS5">
<title>Expression Analysis of <italic>BcTCP</italic> Genes Under Multiple Abiotic Stresses</title>
<p>To investigate the functions of BcTCPs, qPCR was performed to detect the expressions of 26 <italic>BcTCPs</italic> under four treatments (salt, osmotic, cold and ABA) (<xref ref-type="fig" rid="F3">Figure 3</xref>). The results showed that the expressions of most <italic>BcTCPs</italic>, except for <italic>BcTCP12</italic>, were not significantly changed under salt treatment. <italic>BcTCP2</italic>, <italic>3</italic>, <italic>5</italic>, <italic>6</italic>, <italic>7</italic>, <italic>8</italic>, <italic>10</italic>, <italic>12</italic>, <italic>15</italic>, <italic>16</italic>, <italic>17</italic>, <italic>20</italic>, <italic>21</italic>, <italic>22</italic>, <italic>23</italic>, and <italic>24</italic> all up-regulated after 1 h of the ABA treatment. The expression levels of <italic>BcTCP2</italic>, <italic>5</italic>, <italic>6</italic>, <italic>7</italic>, <italic>8</italic>, <italic>10</italic>, <italic>17</italic>, <italic>20</italic>, <italic>21</italic>, <italic>22</italic>, <italic>23</italic>, and <italic>24</italic> reached the maximum at 2 h, <italic>BcTCP15</italic> and <italic>16</italic> had the highest expression at 3h, the largest amount of <italic>BcTCP12</italic> expressed in 4 h, and the largest amount of <italic>BcTCP3</italic> expression quantity in 4 h. Under cold treatment, <italic>BcTCP3</italic>, <italic>6</italic>, <italic>7</italic>, <italic>10</italic>, <italic>12</italic>, <italic>21</italic>, <italic>22</italic>, and <italic>24</italic> showed a significant increase, indicating that these genes, especially <italic>BcTCP21</italic>, may involve in cold stress. Meanwhile, <italic>BcTCP2</italic>, <italic>3</italic>, and <italic>12</italic> were notably up-regulated under osmotic treatment. <italic>BcTCP2</italic> reached its peak at 4 h, and <italic>BcTCP3</italic> and <italic>12</italic> reached their peak at 2 h. These suggested that most <italic>BcTCP</italic> genes were involved in abiotic stresses.</p>
<fig id="F3" position="float">
<label>FIGURE 3</label>
<caption><p>Expression of <italic>BcTCP</italic> genes under different stress treatments. Data shown were means &#x00B1; SE of three independent experiments.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fpls-13-854171-g003.tif"/>
</fig>
</sec>
<sec id="S3.SS6">
<title>Subcellular Localization</title>
<p>WoLF PSORT predicted that BcTCP proteins were localized in the nucleus (<xref ref-type="supplementary-material" rid="TS3">Supplementary Table 3</xref>). To test this, <italic>35S: GFP</italic>, <italic>35S: BcTCP3-GFP</italic>, and <italic>35S: BcTCP21-GFP</italic> constructs were transiently overexpressed in tobacco leaves (<xref ref-type="fig" rid="F4">Figure 4A</xref>). As seen in <xref ref-type="fig" rid="F4">Figure 4B</xref>, <italic>35S: GFP</italic> was localized in the nucleus and cytoplasm. The GFP signals emitted by BcTCP3 -GFP and BcTCP21 -GFP fusion protein were detected in the nucleus and overlapped with the DAPI staining. This results indicated that BcTCP3 and BcTCP21 were nuclear-localized proteins and may function as transcription factors.</p>
<fig id="F4" position="float">
<label>FIGURE 4</label>
<caption><p>Subcellular localization of BcTCP3 protein and BcTCP21 protein: <bold>(A)</bold> <italic>35S: GFP</italic>, <italic>35S: BcTCP3</italic>, and 35S: BcTCP21 construct. <bold>(B)</bold> Transient expression of 35S:GFP, 35S: 35S: BcTCP3-GFP, and 35S: BcTCP21-GFP fusion protein in tobacco leaves (Scale bars = 50 &#x03BC;m).</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fpls-13-854171-g004.tif"/>
</fig>
</sec>
</sec>
<sec id="S4" sec-type="discussion">
<title>Discussion</title>
<p>TCP gene family involves in multiple biological processes, including the circadian clock, abiotic stresses, leaf sizes and shapes, flower development and flowering (<xref ref-type="bibr" rid="B32">Takeda et al., 2006</xref>; <xref ref-type="bibr" rid="B29">Pruneda-Paz et al., 2009</xref>; <xref ref-type="bibr" rid="B24">Mimida et al., 2011</xref>; <xref ref-type="bibr" rid="B27">Niwa et al., 2013</xref>; <xref ref-type="bibr" rid="B18">Liu et al., 2017</xref>; <xref ref-type="bibr" rid="B8">Feng et al., 2018</xref>). The roles of TCP genes under abiotic stresses have been reported in some model plants, such as rice, <italic>Zea mays</italic>, <italic>Arabidopsis thaliana</italic>, and soybean (<xref ref-type="bibr" rid="B30">Rueda-Romero et al., 2012</xref>; <xref ref-type="bibr" rid="B25">Mukhopadhyay and Tyagi, 2015</xref>; <xref ref-type="bibr" rid="B8">Feng et al., 2018</xref>; <xref ref-type="bibr" rid="B4">Ding et al., 2019</xref>). However, virtually less systematic and comprehensive information of the TCP gene family in Pak-choi was reported, which is a nutritious and economically important vegetable crop and widely cultivated in Asia. Unlike <italic>A. thaliana</italic>, <italic>Brassicas</italic> crops not only underwent this complex evolutionary history, but also the whole-genome triplication (WGT) event between 13 and 17 million years ago (MYA). These events were essential for evolution and resulted in differences among species (<xref ref-type="bibr" rid="B35">Wang et al., 2011</xref>). <italic>A. thaliana</italic> has been identified 24 <italic>TCP</italic> genes (<xref ref-type="bibr" rid="B41">Yao et al., 2007</xref>). In this study, 26 <italic>BcTCP</italic> genes were isolated and studied in Pak-choi. These <italic>BcTCP</italic>s were divided into Class I and Class II, Class II was then divided into CIN and CYC/TB1, which was consistent with the previously described in <italic>Arabidopsis</italic>, rice, tomato, and strawberry (<xref ref-type="bibr" rid="B41">Yao et al., 2007</xref>; <xref ref-type="bibr" rid="B28">Parapunova et al., 2014</xref>; <xref ref-type="bibr" rid="B36">Wei et al., 2016</xref>). The phylogenetic analysis found that 16 <italic>AtTCP</italic>s had orthologs in Pak-choi. Among them, <italic>AtTCP1</italic>, <italic>7</italic>, <italic>15</italic>, <italic>18</italic>, <italic>21</italic>, and <italic>24</italic> had more than one ortholog. This indicated that BcTCP family genes and AtTCP family genes may have some similar functions. According to conserved domain, we found that the similarity of BcTCPs in the same class is higher than that of different classes of BcTCPs. For example, CYB/TB1 members all contained motif 1, motif 3, and motif 6. Analysis of promoter regions showed that some <italic>BcTCPs</italic> promoters contained MBS <italic>cis</italic>-regulatory elements, MYB <italic>cis</italic>-regulatory elements, ABRE elements, and G-box, suggesting that the <italic>BcTCP</italic> genes might play significant roles in stress responses (<xref ref-type="bibr" rid="B1">Abe et al., 2003</xref>; <xref ref-type="bibr" rid="B38">Xu et al., 2021</xref>).</p>
<p>QPCR analysis demonstrated that some <italic>BcTCP</italic>s were involved in multiple abiotic stress. For instance, <italic>BcTCP3</italic>, <italic>12</italic>, <italic>21</italic>, <italic>22</italic>, and <italic>24</italic> all responded to cold and ABA treatment. <italic>BcTCP3</italic> had no response to salt stress but had relatively obvious responses under cold and ABA treatments. <italic>BcTCP12</italic> responded to salt, osmotic, ABA, and cold treatments. Under salt treatment, the expression of <italic>BcTCP12</italic> was significantly activated, indicating that <italic>BcTCP12</italic> may enhance salt tolerance, which is same as previous studies in Oryza sativa (<xref ref-type="bibr" rid="B37">Xiao et al., 2009</xref>; <xref ref-type="bibr" rid="B2">Almeida et al., 2017</xref>). The expressions of <italic>BcTCP3</italic>, <italic>5</italic>, <italic>7</italic>, <italic>12</italic>, <italic>21</italic>, <italic>22</italic>, <italic>23</italic>, and <italic>24</italic> displayed more than 30 fold up-regulation under ABA treatment. During drought treatment, <italic>BcTCP2</italic>, <italic>3</italic>, and <italic>12</italic> were up-regulated by more than 15 fold. <italic>BcTCP3</italic>, <italic>12</italic>, <italic>21</italic>, and <italic>22</italic> were also up-regulated by more than 30 fold under cold treatment. These results were consistent with previous research results in rice (<xref ref-type="bibr" rid="B40">Yang et al., 2013</xref>; <xref ref-type="bibr" rid="B34">Wang et al., 2014</xref>). Subcellular localization analysis demonstrated BcTCP3 and BcTCP21 were located in the nucleus, indicating they may function as transcription factors.</p>
<p>These results revealed that <italic>BcTCP</italic>s were associated with multiple abiotic stresses. Our study may be helpful for improving plant stress tolerance. This will provide a piece of vital evidence for detecting the molecular mechanisms of <italic>TCP</italic>s under abiotic stresses. The systematic characterization of <italic>BcTCP</italic>s in Pak-choi will provide a better foundation for further functional studies of this gene family in plant growth and development.</p>
</sec>
<sec id="S5" sec-type="data-availability">
<title>Data Availability Statement</title>
<p>The original contributions presented in the study are included in the article/<xref ref-type="supplementary-material" rid="TS1">Supplementary Material</xref>, further inquiries can be directed to the corresponding author/s.</p>
</sec>
<sec id="S6">
<title>Author Contributions</title>
<p>FH, CS, and YZ completed the experiments and wrote the manuscript. XH revised and approved the manuscript. All authors have read and agreed to the published version of the manuscript.</p>
</sec>
<sec id="conf1" sec-type="COI-statement">
<title>Conflict of Interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="pudiscl1" sec-type="disclaimer">
<title>Publisher&#x2019;s Note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
</body>
<back>
<sec id="S7" sec-type="funding-information">
<title>Funding</title>
<p>This work was supported by grants from the National Natural Science Foundation of China (32102410), the Fundamental Research Funds for the Central Universities (KYQN2022054), the Natural Science Foundation of Jiangsu province (BK20190513), the Key Projects of National Key Research and Development Plan (2017YFD0101803) and the China Agriculture Research System (CARS-23-A-06).</p>
</sec>
<sec id="S8" sec-type="supplementary-material">
<title>Supplementary Material</title>
<p>The Supplementary Material for this article can be found online at: <ext-link ext-link-type="uri" xlink:href="https://www.frontiersin.org/articles/10.3389/fpls.2022.854171/full#supplementary-material">https://www.frontiersin.org/articles/10.3389/fpls.2022.854171/full#supplementary-material</ext-link></p>
<supplementary-material xlink:href="Table_1.XLSX" id="TS1" mimetype="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" xmlns:xlink="http://www.w3.org/1999/xlink"/>
<supplementary-material xlink:href="Table_2.XLSX" id="TS2" mimetype="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" xmlns:xlink="http://www.w3.org/1999/xlink"/>
<supplementary-material xlink:href="Table_3.xlsx" id="TS3" mimetype="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" xmlns:xlink="http://www.w3.org/1999/xlink"/>
</sec>
<ref-list>
<title>References</title>
<ref id="B1"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Abe</surname> <given-names>H.</given-names></name> <name><surname>Urao</surname> <given-names>T.</given-names></name> <name><surname>Ito</surname> <given-names>T.</given-names></name> <name><surname>Seki</surname> <given-names>M.</given-names></name> <name><surname>Shinozaki</surname> <given-names>K.</given-names></name> <name><surname>Yamaguchi-Shinozaki</surname> <given-names>K.</given-names></name></person-group> (<year>2003</year>). <article-title><italic>Arabidopsis</italic> AtMYC2 (bHLH) and AtMYB2 (MYB) Function as Transcriptional Activators in Abscisic Acid Signaling.</article-title> <source><italic>Plant Cell</italic></source> <volume>155</volume> <fpage>63</fpage>&#x2013;<lpage>78</lpage>. <pub-id pub-id-type="doi">10.1105/tpc.006130</pub-id> <pub-id pub-id-type="pmid">12509522</pub-id></citation></ref>
<ref id="B2"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Almeida</surname> <given-names>D. M.</given-names></name> <name><surname>Gregorio</surname> <given-names>G. B.</given-names></name> <name><surname>Oliveira</surname> <given-names>M. M.</given-names></name> <name><surname>Saibo</surname> <given-names>N. J. M.</given-names></name></person-group> (<year>2017</year>). <article-title>Five noveln transcription factors as potential regulators of <italic>OsNHX1</italic> gene expression in a salt tolerant rice genotype.</article-title> <source><italic>Plant Mol. Biol.</italic></source> <volume>93</volume> <fpage>61</fpage>&#x2013;<lpage>77</lpage>. <pub-id pub-id-type="doi">10.1007/s11103-016-0547-7</pub-id> <pub-id pub-id-type="pmid">27766460</pub-id></citation></ref>
<ref id="B3"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Boudsocq</surname> <given-names>M.</given-names></name> <name><surname>Lauri&#x00E8;re</surname> <given-names>C.</given-names></name></person-group> (<year>2005</year>). <article-title>Osmotic Signaling in Plants. Multiple Pathways Mediated by Emerging Kinase Families.</article-title> <source><italic>Plant Physiol.</italic></source> <volume>138</volume> <fpage>1185</fpage>&#x2013;<lpage>1194</lpage>. <pub-id pub-id-type="doi">10.1104/pp.105.061275</pub-id> <pub-id pub-id-type="pmid">16009994</pub-id></citation></ref>
<ref id="B4"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ding</surname> <given-names>S.</given-names></name> <name><surname>Cai</surname> <given-names>Z.</given-names></name> <name><surname>Du</surname> <given-names>H.</given-names></name> <name><surname>Wang</surname> <given-names>H.</given-names></name></person-group> (<year>2019</year>). <article-title>Genome-Wide Analysis of TCP Family Genes in <italic>Zea mays</italic> L. Identified a Role for <italic>ZmTCP42</italic> in Drought Tolerance.</article-title> <source><italic>Int. J. Mol. Sci.</italic></source> <volume>20</volume>:<issue>2762</issue>. <pub-id pub-id-type="doi">10.3390/ijms20112762</pub-id> <pub-id pub-id-type="pmid">31195663</pub-id></citation></ref>
<ref id="B5"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Doebley</surname> <given-names>J.</given-names></name> <name><surname>Stec</surname> <given-names>A.</given-names></name> <name><surname>Gustus</surname> <given-names>C.</given-names></name></person-group> (<year>1995</year>). <article-title><italic>teosinte branched1</italic> and the Origin of Maize: evidence for Epistasis and the Evolution of Dominance.</article-title> <source><italic>Genetics</italic></source> <volume>141</volume> <fpage>333</fpage>&#x2013;<lpage>346</lpage>. <pub-id pub-id-type="doi">10.1093/genetics/141.1.333</pub-id> <pub-id pub-id-type="pmid">8536981</pub-id></citation></ref>
<ref id="B6"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Doebley</surname> <given-names>J.</given-names></name> <name><surname>Stec</surname> <given-names>A.</given-names></name> <name><surname>Hubbard</surname> <given-names>L.</given-names></name></person-group> (<year>1997</year>). <article-title>The evolution of apical dominance in maize.</article-title> <source><italic>Nature</italic></source> <volume>386</volume> <fpage>485</fpage>&#x2013;<lpage>488</lpage>. <pub-id pub-id-type="doi">10.1038/386485a0</pub-id> <pub-id pub-id-type="pmid">9087405</pub-id></citation></ref>
<ref id="B7"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Du</surname> <given-names>J.</given-names></name> <name><surname>Hu</surname> <given-names>S.</given-names></name> <name><surname>Yu</surname> <given-names>Q.</given-names></name> <name><surname>Wang</surname> <given-names>C.</given-names></name> <name><surname>Yang</surname> <given-names>Y.</given-names></name> <name><surname>Sun</surname> <given-names>H.</given-names></name><etal/></person-group> (<year>2017</year>). <article-title>Genome-Wide Identification and Characterization of BrrTCP Transcription Factors in <italic>Brassica rapa</italic> ssp. <italic>rapa</italic>.</article-title> <source><italic>Front. Plant Sci.</italic></source> <volume>8</volume>:<issue>1588</issue>. <pub-id pub-id-type="doi">10.3389/fpls.2017.01588</pub-id> <pub-id pub-id-type="pmid">28955373</pub-id></citation></ref>
<ref id="B8"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Feng</surname> <given-names>Z. J.</given-names></name> <name><surname>Xu</surname> <given-names>S. C.</given-names></name> <name><surname>Liu</surname> <given-names>N.</given-names></name> <name><surname>Zhang</surname> <given-names>G. W.</given-names></name> <name><surname>Hu</surname> <given-names>Q. Z.</given-names></name> <name><surname>Gong</surname> <given-names>Y. M.</given-names></name></person-group> (<year>2018</year>). <article-title>Soybean TCP transcription factors: evolution, classification, protein interaction and stress and hormone responsiveness.</article-title> <source><italic>Plant Physiol. Biochem.</italic></source> <volume>127</volume> <fpage>129</fpage>&#x2013;<lpage>142</lpage>. <pub-id pub-id-type="doi">10.1016/j.plaphy.2018.03.020</pub-id> <pub-id pub-id-type="pmid">29579640</pub-id></citation></ref>
<ref id="B9"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Fujita</surname> <given-names>Y.</given-names></name> <name><surname>Fujita</surname> <given-names>M.</given-names></name> <name><surname>Shinozaki</surname> <given-names>K.</given-names></name> <name><surname>Yamaguchi-Shinozaki</surname> <given-names>K.</given-names></name></person-group> (<year>2011</year>). <article-title>ABA-mediated transcriptional regulation in response to osmotic stress in plants.</article-title> <source><italic>J. Plant Res.</italic></source> <volume>124</volume> <fpage>509</fpage>&#x2013;<lpage>525</lpage>. <pub-id pub-id-type="doi">10.1007/s10265-011-0412-3</pub-id> <pub-id pub-id-type="pmid">21416314</pub-id></citation></ref>
<ref id="B10"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Guan</surname> <given-names>P.</given-names></name> <name><surname>Ripoll</surname> <given-names>J. J.</given-names></name> <name><surname>Wang</surname> <given-names>R.</given-names></name> <name><surname>Vuong</surname> <given-names>L.</given-names></name> <name><surname>Bailey-Steinitz</surname> <given-names>L. J.</given-names></name> <name><surname>Ye</surname> <given-names>D.</given-names></name><etal/></person-group> (<year>2017</year>). <article-title>Interacting TCP and NLP transcription factors control plant responses to nitrate availability.</article-title> <source><italic>Proc. Natl. Acad. Sci. U. S. A.</italic></source> <volume>114</volume> <fpage>2419</fpage>&#x2013;<lpage>2424</lpage>. <pub-id pub-id-type="doi">10.1073/pnas.1615676114</pub-id> <pub-id pub-id-type="pmid">28202720</pub-id></citation></ref>
<ref id="B11"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Huang</surname> <given-names>F. Y.</given-names></name> <name><surname>Liu</surname> <given-names>T. K.</given-names></name> <name><surname>Tang</surname> <given-names>J.</given-names></name> <name><surname>Duan</surname> <given-names>W. K.</given-names></name> <name><surname>Hou</surname> <given-names>X. L.</given-names></name></person-group> (<year>2019</year>). <article-title>BcMAF2 activates <italic>BcTEM1</italic> and represses flowering in Pak-choi (<italic>Brassica rapa</italic> ssp. <italic>chinensis</italic>).</article-title> <source><italic>Plant Mol. Biol.</italic></source> <volume>100</volume> <fpage>19</fpage>&#x2013;<lpage>32</lpage>. <pub-id pub-id-type="doi">10.1007/s11103-019-00867-1</pub-id> <pub-id pub-id-type="pmid">31001712</pub-id></citation></ref>
<ref id="B12"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Huo</surname> <given-names>Y.</given-names></name> <name><surname>Xiong</surname> <given-names>W.</given-names></name> <name><surname>Su</surname> <given-names>K.</given-names></name> <name><surname>Li</surname> <given-names>Y.</given-names></name> <name><surname>Yang</surname> <given-names>Y.</given-names></name> <name><surname>Fu</surname> <given-names>C.</given-names></name><etal/></person-group> (<year>2019</year>). <article-title>Genome-Wide Analysis of the <italic>TCP</italic> Gene Family in Switchgrass (<italic>Panicum virgatum</italic> L.).</article-title> <source><italic>Int. J. Genomics</italic></source> <volume>2019</volume> <fpage>1</fpage>&#x2013;<lpage>13</lpage>. <pub-id pub-id-type="doi">10.1155/2019/8514928</pub-id> <pub-id pub-id-type="pmid">31093492</pub-id></citation></ref>
<ref id="B13"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kim</surname> <given-names>T. H.</given-names></name> <name><surname>B&#x00F6;hmer</surname> <given-names>M.</given-names></name> <name><surname>Hu</surname> <given-names>H.</given-names></name> <name><surname>Nishimura</surname> <given-names>N.</given-names></name> <name><surname>Schroeder</surname> <given-names>J. I.</given-names></name></person-group> (<year>2010</year>). <article-title>Guard Cell Signal Transduction Network: advances in Understanding Abscisic Acid, CO<sub>2</sub>, and Ca<sup>2+</sup> Signaling.</article-title> <source><italic>Annu. Rev. Plant Biol.</italic></source> <volume>61</volume> <fpage>561</fpage>&#x2013;<lpage>591</lpage>. <pub-id pub-id-type="doi">10.1146/annurev-arplant-042809-112226</pub-id> <pub-id pub-id-type="pmid">20192751</pub-id></citation></ref>
<ref id="B14"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kosugi</surname> <given-names>S.</given-names></name> <name><surname>Ohashi</surname> <given-names>Y.</given-names></name></person-group> (<year>1997</year>). <article-title>PCF1 and PCF2 Specifically Bind to <italic>cis</italic> Elements in the Rice Proliferating Cell Nuclear Antigen Gene.</article-title> <source><italic>Plant Cell</italic></source> <volume>9</volume> <fpage>1607</fpage>&#x2013;<lpage>1619</lpage>. <pub-id pub-id-type="doi">10.2307/3870447</pub-id></citation></ref>
<ref id="B15"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kosugi</surname> <given-names>S.</given-names></name> <name><surname>Ohashi</surname> <given-names>Y.</given-names></name></person-group> (<year>2002</year>). <article-title>DNA binding and dimerization specificity and potential targets for the TCP protein family.</article-title> <source><italic>Plant J.</italic></source> <volume>30</volume> <fpage>337</fpage>&#x2013;<lpage>348</lpage>. <pub-id pub-id-type="doi">10.1046/j.1365-313X.2002.01294.x</pub-id> <pub-id pub-id-type="pmid">12000681</pub-id></citation></ref>
<ref id="B16"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Li</surname> <given-names>S.</given-names></name></person-group> (<year>2015</year>). <article-title>The <italic>Arabidopsis thaliana</italic> TCP transcription factors: a broadening horizon beyond development.</article-title> <source><italic>Plant Signal. Behav.</italic></source> <volume>10</volume>:<issue>e1044192</issue>. <pub-id pub-id-type="doi">10.1080/15592324.2015.1044192</pub-id> <pub-id pub-id-type="pmid">26039357</pub-id></citation></ref>
<ref id="B17"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ling</surname> <given-names>L.</given-names></name> <name><surname>Zhang</surname> <given-names>W.</given-names></name> <name><surname>An</surname> <given-names>Y.</given-names></name> <name><surname>Du</surname> <given-names>B.</given-names></name> <name><surname>Wang</surname> <given-names>D.</given-names></name> <name><surname>Guo</surname> <given-names>C.</given-names></name></person-group> (<year>2020</year>). <article-title>Genome-wide analysis of the <italic>TCP</italic> transcription factor genes in five legume genomes and their response to salt and drought stresses.</article-title> <source><italic>Funct. Integr. Genomics</italic></source> <volume>20</volume> <fpage>537</fpage>&#x2013;<lpage>550</lpage>. <pub-id pub-id-type="doi">10.1007/s10142-020-00733-0</pub-id> <pub-id pub-id-type="pmid">32034565</pub-id></citation></ref>
<ref id="B18"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Liu</surname> <given-names>J.</given-names></name> <name><surname>Cheng</surname> <given-names>X.</given-names></name> <name><surname>Liu</surname> <given-names>P.</given-names></name> <name><surname>Li</surname> <given-names>D.</given-names></name> <name><surname>Chen</surname> <given-names>T.</given-names></name> <name><surname>Gu</surname> <given-names>X.</given-names></name><etal/></person-group> (<year>2017</year>). <article-title>MicroRNA319-regulated TCPs interact with FBHs and PFT1 to activate <italic>CO</italic> transcription and control flowering time in <italic>Arabidopsis</italic>.</article-title> <source><italic>PLoS Genet.</italic></source> <volume>13</volume>:<issue>e1006833</issue>. <pub-id pub-id-type="doi">10.1371/journal.pgen.1006833</pub-id> <pub-id pub-id-type="pmid">28558040</pub-id></citation></ref>
<ref id="B19"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Liu</surname> <given-names>M. M.</given-names></name> <name><surname>Wang</surname> <given-names>M. M.</given-names></name> <name><surname>Yang</surname> <given-names>J.</given-names></name> <name><surname>Wen</surname> <given-names>J.</given-names></name> <name><surname>Guo</surname> <given-names>P. C.</given-names></name> <name><surname>Wu</surname> <given-names>Y. W.</given-names></name><etal/></person-group> (<year>2019</year>). <article-title>Evolutionary and Comparative Expression Analyses of TCP Transcription Factor Gene Family in Land Plants.</article-title> <source><italic>Int. J. Mol. Sci.</italic></source> <volume>20</volume>:<issue>3591</issue>. <pub-id pub-id-type="doi">10.3390/ijms20143591</pub-id> <pub-id pub-id-type="pmid">31340456</pub-id></citation></ref>
<ref id="B20"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Livak</surname> <given-names>K. J.</given-names></name> <name><surname>Schmittgen</surname> <given-names>T. D.</given-names></name></person-group> (<year>2001</year>). <article-title>Analysis of Relative Gene Expression Data Using Realtime Quantitative PCR and the 2<sup>&#x2013;&#x0394;&#x0394;CT</sup> Method.</article-title> <source><italic>Methods</italic></source> <volume>25</volume> <fpage>402</fpage>&#x2013;<lpage>408</lpage>. <pub-id pub-id-type="doi">10.1006/meth.2001</pub-id></citation></ref>
<ref id="B21"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Luo</surname> <given-names>D.</given-names></name> <name><surname>Carpenter</surname> <given-names>R.</given-names></name> <name><surname>Vincent</surname> <given-names>C.</given-names></name> <name><surname>Copsey</surname> <given-names>L.</given-names></name> <name><surname>Coen</surname> <given-names>E.</given-names></name></person-group> (<year>1996</year>). <article-title>Origin of floral asymmetry in <italic>Antirrhinum</italic>.</article-title> <source><italic>Nature</italic></source> <volume>383</volume> <fpage>794</fpage>&#x2013;<lpage>799</lpage>. <pub-id pub-id-type="doi">10.1038/383794a0</pub-id> <pub-id pub-id-type="pmid">8893002</pub-id></citation></ref>
<ref id="B22"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ma</surname> <given-names>X.</given-names></name> <name><surname>Ma</surname> <given-names>J.</given-names></name> <name><surname>Fan</surname> <given-names>D.</given-names></name> <name><surname>Li</surname> <given-names>C.</given-names></name> <name><surname>Jiang</surname> <given-names>Y.</given-names></name> <name><surname>Luo</surname> <given-names>K.</given-names></name></person-group> (<year>2016</year>). <article-title>Genome-wide Identification of TCP Family Transcription Factors from <italic>Populus euphratica</italic> and their Involvement in Leaf Shape Regulation.</article-title> <source><italic>Sci. Rep.</italic></source> <volume>6</volume>:<issue>32795</issue>. <pub-id pub-id-type="doi">10.1038/srep32795</pub-id> <pub-id pub-id-type="pmid">27605130</pub-id></citation></ref>
<ref id="B23"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Martin-Trillo</surname> <given-names>M.</given-names></name> <name><surname>Cubas</surname> <given-names>P.</given-names></name></person-group> (<year>2010</year>). <article-title>TCP genes: a family snapshot ten years later.</article-title> <source><italic>Trends Plant Sci.</italic></source> <volume>15</volume> <fpage>31</fpage>&#x2013;<lpage>39</lpage>. <pub-id pub-id-type="doi">10.1016/j.tplants.2009.11.003</pub-id> <pub-id pub-id-type="pmid">19963426</pub-id></citation></ref>
<ref id="B24"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Mimida</surname> <given-names>N.</given-names></name> <name><surname>Kidou</surname> <given-names>S.</given-names></name> <name><surname>Iwanami</surname> <given-names>H.</given-names></name> <name><surname>Moriya</surname> <given-names>S.</given-names></name> <name><surname>Abe</surname> <given-names>K.</given-names></name> <name><surname>Voogd</surname> <given-names>C.</given-names></name><etal/></person-group> (<year>2011</year>). <article-title>Apple FLOWERING LOCUS T proteins interact with transcription factors implicated in cell growth and organ development.</article-title> <source><italic>Tree Physiol.</italic></source> <volume>31</volume> <fpage>555</fpage>&#x2013;<lpage>566</lpage>. <pub-id pub-id-type="doi">10.1093/treephys/tpr028</pub-id> <pub-id pub-id-type="pmid">21571725</pub-id></citation></ref>
<ref id="B25"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Mukhopadhyay</surname> <given-names>P.</given-names></name> <name><surname>Tyagi</surname> <given-names>A. K.</given-names></name></person-group> (<year>2015</year>). <article-title><italic>OsTCP19</italic> influences developmental and abiotic stress signaling by modulating ABI4-mediated pathways.</article-title> <source><italic>Sci. Rep.</italic></source> <volume>5</volume>:<issue>9998</issue>. <pub-id pub-id-type="doi">10.1038/srep09998</pub-id> <pub-id pub-id-type="pmid">25925167</pub-id></citation></ref>
<ref id="B26"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Navaud</surname> <given-names>O.</given-names></name> <name><surname>Dabos</surname> <given-names>P.</given-names></name> <name><surname>Carnus</surname> <given-names>E.</given-names></name> <name><surname>Tremousaygue</surname> <given-names>D.</given-names></name> <name><surname>Herv&#x00E9;</surname> <given-names>C.</given-names></name></person-group> (<year>2007</year>). <article-title>TCP Transcription Factors Predate the Emergence of Land Plants.</article-title> <source><italic>J. Mol. Evol.</italic></source> <volume>65</volume> <fpage>23</fpage>&#x2013;<lpage>33</lpage>. <pub-id pub-id-type="doi">10.1007/s00239-006-0174-z</pub-id> <pub-id pub-id-type="pmid">17568984</pub-id></citation></ref>
<ref id="B27"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Niwa</surname> <given-names>M.</given-names></name> <name><surname>Daimon</surname> <given-names>Y.</given-names></name> <name><surname>Kurotani</surname> <given-names>K.</given-names></name> <name><surname>Higo</surname> <given-names>A.</given-names></name> <name><surname>Pruneda-Paz</surname> <given-names>J. L.</given-names></name> <name><surname>Breton</surname> <given-names>G.</given-names></name><etal/></person-group> (<year>2013</year>). <article-title>BRANCHED1 Interacts with FLOWERING LOCUS T to Repress the Floral Transition of the Axillary Meristems in <italic>Arabidopsis</italic>.</article-title> <source><italic>Plant Cell</italic></source> <volume>25</volume> <fpage>1228</fpage>&#x2013;<lpage>1242</lpage>. <pub-id pub-id-type="doi">10.1105/tpc.112.109090</pub-id> <pub-id pub-id-type="pmid">23613197</pub-id></citation></ref>
<ref id="B28"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Parapunova</surname> <given-names>V.</given-names></name> <name><surname>Busscher</surname> <given-names>M.</given-names></name> <name><surname>Busscher-Lange</surname> <given-names>J.</given-names></name> <name><surname>Lammers</surname> <given-names>M.</given-names></name> <name><surname>Karlova</surname> <given-names>R.</given-names></name> <name><surname>Bovy</surname> <given-names>A. G.</given-names></name><etal/></person-group> (<year>2014</year>). <article-title>Identification, cloning and characterization of the tomato TCP transcription factor family.</article-title> <source><italic>BMC Plant Biol.</italic></source> <volume>14</volume>:<issue>157</issue>. <pub-id pub-id-type="doi">10.1186/1471-2229-14-157</pub-id> <pub-id pub-id-type="pmid">24903607</pub-id></citation></ref>
<ref id="B29"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Pruneda-Paz</surname> <given-names>J. L.</given-names></name> <name><surname>Breton</surname> <given-names>G.</given-names></name> <name><surname>Para</surname> <given-names>A.</given-names></name> <name><surname>Kay</surname> <given-names>S. A.</given-names></name></person-group> (<year>2009</year>). <article-title>A functional genomics approach reveals CHE as a component of the <italic>Arabidopsis</italic> circadian clock.</article-title> <source><italic>Science</italic></source> <volume>323</volume> <fpage>1481</fpage>&#x2013;<lpage>1485</lpage>. <pub-id pub-id-type="doi">10.1126/science.1167206</pub-id> <pub-id pub-id-type="pmid">19286557</pub-id></citation></ref>
<ref id="B30"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Rueda-Romero</surname> <given-names>P.</given-names></name> <name><surname>Barrero-Sicilia</surname> <given-names>C.</given-names></name> <name><surname>G&#x00F3;mez-Cadenas</surname> <given-names>A.</given-names></name> <name><surname>Carbonero</surname> <given-names>P.</given-names></name> <name><surname>O&#x00F1;ate-S&#x00E1;nchez</surname> <given-names>L.</given-names></name></person-group> (<year>2012</year>). <article-title><italic>Arabidopsis thaliana</italic> DOF6 negatively affects germination in non-after-ripened seeds and interacts with TCP14.</article-title> <source><italic>J. Exp. Bot.</italic></source> <volume>63</volume> <fpage>1937</fpage>&#x2013;<lpage>1949</lpage>. <pub-id pub-id-type="doi">10.1093/jxb/err388</pub-id> <pub-id pub-id-type="pmid">22155632</pub-id></citation></ref>
<ref id="B31"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Shibasaki</surname> <given-names>K.</given-names></name> <name><surname>Uemura</surname> <given-names>M.</given-names></name> <name><surname>Tsurumi</surname> <given-names>S.</given-names></name> <name><surname>Rahman</surname> <given-names>A.</given-names></name></person-group> (<year>2009</year>). <article-title>Auxin Response in <italic>Arabidopsis</italic> under Cold Stress: underlying Molecular Mechanisms.</article-title> <source><italic>Plant Cell</italic></source> <volume>21</volume> <fpage>3823</fpage>&#x2013;<lpage>3838</lpage>. <pub-id pub-id-type="doi">10.1105/tpc.109.069906</pub-id> <pub-id pub-id-type="pmid">20040541</pub-id></citation></ref>
<ref id="B32"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Takeda</surname> <given-names>T.</given-names></name> <name><surname>Amano</surname> <given-names>K.</given-names></name> <name><surname>Ohto</surname> <given-names>M. A.</given-names></name> <name><surname>Nakamura</surname> <given-names>K.</given-names></name> <name><surname>Sato</surname> <given-names>S.</given-names></name> <name><surname>Kato</surname> <given-names>T.</given-names></name><etal/></person-group> (<year>2006</year>). <article-title>RNA interference of the <italic>Arabidopsis</italic> putative transcription factor <italic>TCP16</italic> gene results in abortion of early pollen development.</article-title> <source><italic>Plant Mol. Biol.</italic></source> <volume>61</volume> <fpage>165</fpage>&#x2013;<lpage>177</lpage>. <pub-id pub-id-type="doi">10.1007/s11103-006-6265-9</pub-id> <pub-id pub-id-type="pmid">16786299</pub-id></citation></ref>
<ref id="B33"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Tian</surname> <given-names>C.</given-names></name> <name><surname>Wan</surname> <given-names>P.</given-names></name> <name><surname>Sun</surname> <given-names>S.</given-names></name> <name><surname>Li</surname> <given-names>J.</given-names></name> <name><surname>Chen</surname> <given-names>M.</given-names></name></person-group> (<year>2004</year>). <article-title>Genome-wide analysis of the GRAS gene family in rice and <italic>Arabidopsis</italic>.</article-title> <source><italic>Plant Mol. Biol.</italic></source> <volume>54</volume> <fpage>519</fpage>&#x2013;<lpage>532</lpage>. <pub-id pub-id-type="doi">10.1023/B:PLAN.0000038256.89809.57</pub-id></citation></ref>
<ref id="B34"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wang</surname> <given-names>S. T.</given-names></name> <name><surname>Sun</surname> <given-names>X. L.</given-names></name> <name><surname>Hoshino</surname> <given-names>Y.</given-names></name> <name><surname>Yu</surname> <given-names>Y.</given-names></name> <name><surname>Jia</surname> <given-names>B.</given-names></name> <name><surname>Sun</surname> <given-names>Z. W.</given-names></name><etal/></person-group> (<year>2014</year>). <article-title><italic>MicroRNA319</italic> Positively Regulates Cold Tolerance by Targeting <italic>OsPCF6</italic> and <italic>OsTCP21</italic> in Rice (<italic>Oryza sativa</italic> L.).</article-title> <source><italic>PLoS One</italic></source> <volume>9</volume>:<issue>e91357</issue>. <pub-id pub-id-type="doi">10.1371/journal.pone.0091357</pub-id> <pub-id pub-id-type="pmid">24667308</pub-id></citation></ref>
<ref id="B35"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wang</surname> <given-names>X. W.</given-names></name> <name><surname>Wang</surname> <given-names>H. Z.</given-names></name> <name><surname>Wang</surname> <given-names>J.</given-names></name> <name><surname>Sun</surname> <given-names>R.</given-names></name> <name><surname>Wu</surname> <given-names>J.</given-names></name> <name><surname>Liu</surname> <given-names>S. Y.</given-names></name><etal/></person-group> (<year>2011</year>). <article-title>The genome of the mesopolyploid crop species <italic>Brassica rapa</italic>.</article-title> <source><italic>Nat. Genet.</italic></source> <volume>43</volume> <fpage>1035</fpage>&#x2013;<lpage>1039</lpage>. <pub-id pub-id-type="doi">10.1038/ng.919</pub-id> <pub-id pub-id-type="pmid">21873998</pub-id></citation></ref>
<ref id="B36"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wei</surname> <given-names>W.</given-names></name> <name><surname>Hu</surname> <given-names>Y.</given-names></name> <name><surname>Cui</surname> <given-names>M. Y.</given-names></name> <name><surname>Han</surname> <given-names>Y. T.</given-names></name> <name><surname>Gao</surname> <given-names>K.</given-names></name> <name><surname>Feng</surname> <given-names>J. Y.</given-names></name></person-group> (<year>2016</year>). <article-title>Identification and Transcript Analysis of the TCP Transcription Factors in the Diploid Woodland Strawberry <italic>Fragaria vesca</italic>.</article-title> <source><italic>Front. Plant Sci.</italic></source> <volume>7</volume>:<issue>1937</issue>. <pub-id pub-id-type="doi">10.3389/fpls.2016.01937</pub-id> <pub-id pub-id-type="pmid">28066489</pub-id></citation></ref>
<ref id="B37"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Xiao</surname> <given-names>B. Z.</given-names></name> <name><surname>Chen</surname> <given-names>X.</given-names></name> <name><surname>Xiang</surname> <given-names>C. B.</given-names></name> <name><surname>Tang</surname> <given-names>N.</given-names></name> <name><surname>Zhang</surname> <given-names>Q. F.</given-names></name> <name><surname>Xiong</surname> <given-names>L. Z.</given-names></name></person-group> (<year>2009</year>). <article-title>Evaluation of Seven Function-Known Candidate Genes for their Effects on Improving Drought Resistance of Transgenic Rice under Field Conditions.</article-title> <source><italic>Mol. Plant</italic></source> <volume>2</volume> <fpage>73</fpage>&#x2013;<lpage>83</lpage>. <pub-id pub-id-type="doi">10.1093/mp/ssn068</pub-id> <pub-id pub-id-type="pmid">19529831</pub-id></citation></ref>
<ref id="B38"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Xu</surname> <given-names>J. L.</given-names></name> <name><surname>Zhang</surname> <given-names>W. J.</given-names></name> <name><surname>Xiang</surname> <given-names>F. N.</given-names></name></person-group> (<year>2021</year>). <article-title>Advances in stress inducible promoter and <italic>cis-acting</italic> elements in higher plants.</article-title> <source><italic>J. Plant Physiol.</italic></source> <volume>57</volume> <fpage>759</fpage>&#x2013;<lpage>766</lpage>. <pub-id pub-id-type="doi">10.13592/j.cnki.ppj.2020.0221</pub-id></citation></ref>
<ref id="B39"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Yamaguchi-Shinozaki</surname> <given-names>K.</given-names></name> <name><surname>Shinozaki</surname> <given-names>K.</given-names></name></person-group> (<year>2006</year>). <article-title>Transcriptional Regulatory Networks in Cellular Responses and Tolerance to Dehydration and Cold Stresses.</article-title> <source><italic>Annu. Rev. Plant Biol.</italic></source> <volume>57</volume> <fpage>781</fpage>&#x2013;<lpage>803</lpage>. <pub-id pub-id-type="doi">10.1146/annurev.arplant.57.032905.105444</pub-id> <pub-id pub-id-type="pmid">16669782</pub-id></citation></ref>
<ref id="B40"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Yang</surname> <given-names>C.</given-names></name> <name><surname>Li</surname> <given-names>D.</given-names></name> <name><surname>Mao</surname> <given-names>D.</given-names></name> <name><surname>Liu</surname> <given-names>X.</given-names></name> <name><surname>Ji</surname> <given-names>C.</given-names></name> <name><surname>Li</surname> <given-names>X.</given-names></name><etal/></person-group> (<year>2013</year>). <article-title>Overexpression of microRNA319 impacts leaf morphogenesis and leads to enhanced cold tolerance in rice (<italic>Oryza sativa</italic> L.).</article-title> <source><italic>Plant Cell Environ.</italic></source> <volume>36</volume> <fpage>2207</fpage>&#x2013;<lpage>2218</lpage>. <pub-id pub-id-type="doi">10.1111/pce.12130</pub-id> <pub-id pub-id-type="pmid">23651319</pub-id></citation></ref>
<ref id="B41"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Yao</surname> <given-names>X.</given-names></name> <name><surname>Ma</surname> <given-names>H.</given-names></name> <name><surname>Wang</surname> <given-names>J.</given-names></name> <name><surname>Zhang</surname> <given-names>D. B.</given-names></name></person-group> (<year>2007</year>). <article-title>Genome-Wide Comparative Analysis and Expression Pattern of TCP Gene Families in <italic>Arabidopsis thaliana</italic> and <italic>Oryza sativa</italic>.</article-title> <source><italic>J. Integr. Plant Biol.</italic></source> <volume>49</volume> <fpage>885</fpage>&#x2013;<lpage>897</lpage>. <pub-id pub-id-type="doi">10.1111/j.1744-7909.2007.00509.x</pub-id></citation></ref>
<ref id="B42"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Zhou</surname> <given-names>M.</given-names></name> <name><surname>Li</surname> <given-names>D.</given-names></name> <name><surname>Li</surname> <given-names>Z.</given-names></name> <name><surname>Hu</surname> <given-names>Q.</given-names></name> <name><surname>Yang</surname> <given-names>C.</given-names></name> <name><surname>Zhu</surname> <given-names>L.</given-names></name><etal/></person-group> (<year>2013</year>). <article-title>Constitutive Expression of a <italic>miR319</italic> Gene Alters Plant Development and Enhances Salt and Drought Tolerance in Transgenic Creeping Bentgrass.</article-title> <source><italic>Plant Physiol.</italic></source> <volume>161</volume> <fpage>1375</fpage>&#x2013;<lpage>1391</lpage>. <pub-id pub-id-type="doi">10.1104/pp.112.208702</pub-id> <pub-id pub-id-type="pmid">23292790</pub-id></citation></ref>
</ref-list>
<fn-group>
<fn id="footnote1">
<label>1</label>
<p><ext-link ext-link-type="uri" xlink:href="http://pfam.xfam.org/">http://pfam.xfam.org/</ext-link></p></fn>
<fn id="footnote2">
<label>2</label>
<p><ext-link ext-link-type="uri" xlink:href="https://web.expasy.org/protparam/">https://web.expasy.org/protparam/</ext-link></p></fn>
<fn id="footnote3">
<label>3</label>
<p><ext-link ext-link-type="uri" xlink:href="https://www.arabidopsis.org/">https://www.arabidopsis.org/</ext-link></p></fn>
<fn id="footnote4">
<label>4</label>
<p><ext-link ext-link-type="uri" xlink:href="http://bioinformatics.psb.ugent.be/webtools/plantcare/html/">http://bioinformatics.psb.ugent.be/webtools/plantcare/html/</ext-link></p></fn>
<fn id="footnote5">
<label>5</label>
<p><ext-link ext-link-type="uri" xlink:href="http://meme-suite.org/">http://meme-suite.org/</ext-link></p></fn>
<fn id="footnote6">
<label>6</label>
<p><ext-link ext-link-type="uri" xlink:href="http://wolfpsort.org/">http://wolfpsort.org/</ext-link></p></fn>
</fn-group>
</back>
</article>
