The MYB transcription factor family is a group of highly conserved DNA-binding domains known as MYB transcription factor structural domains. Each MYB transcription factor contains one to four repetitive MYB domains. Each repeat has approximately 52 amino acid residues, which are inserted into the main groove of double-stranded DNA in a helix-rotate-helix conformation. Each MYB repeat contains three α-helix connected by a corner between the second and third helices to form a stable helix-turn-helix (H-T-H). In the MYB domain sequence, there is a tryptophan residue (W) between every 18–19 amino acid residues, whose main function is to form a hydrophobic core in the H-T-H three-dimensional structure. The HTH three-dimensional structure consists of three regularly spaced hydrophobic amino acids, usually Trp, which are sometimes replaced by Phe or Leu, and which form a hydrophobic core, which is critical for the maintenance of the spatial conformation of MYBs. The third helix is considered to be the ‘recognition helix’ and is responsible for recognizing the DNA binding site and structurally binding to the target DNA in the major groove ( Figure 2 ) (Yang et al., 2022a).

The presence of three regularly spaced tryptophan in each MYB repeat sequence forms a hydrophobic cluster that is associated with specific recognition of the DNA sequence (Li et al., 2022b). Based on the similarity to the three repeat sequences R1, R2, or R3 in animal c-myb and the number of R repeat sequences, the plant MYB TFs family has been classified into four categories: MYB TFs are classified as 1R-MYB, R2R3-MYB (majority), R3-MYB, R4-MYB and MYB-like (MYB-related) ( Figure 3 ) (Dubos et al., 2010).

In 1987, scientists cloned the first plant MYB-like transcription factor gene COLORED1 from maize. Its encoded protein ZmMYBC1 and found that ZmMYBC1 is mainly involved in anthocyanin synthesis, and nowadays it is one of the most abundant classes of MYB TFs in plants (Pazares et al., 1987). Nowadays, researchers have found from Arabidopsis thaliana L., Capsicum annuum L., Spinacia oleracea L., Oryza sativa L., and other species ( Table 1 ). A large number of MYB genes have been identified in plants. So far, a cumulative total of 198 MYB genes have been identified in the Arabidopsis thaliana L. genome and a cumulative total of 239 MYB genes have been identified in the Oryza sativa genome. From the table, we can find that the number of MYB family members in different species showed some differences, but the number of MYB genes encoding R2R3-MYB was higher than that of other MYB genes in most species. Thus, R2R3-MYB is the most abundant subclass of the MYB family in most plants, and it exists in many monocotyledonous and dicotyledonous plants. The MYB transcription factors are widely involved in plant growth and development, cell differentiation, metabolic pathway regulation, and abiotic stress response (Muthuramalingam et al., 2022; Liu et al., 2024b; Prusty et al., 2024; Wu et al., 2022).

By selecting Arabidopsis thaliana L., Oryza sativa and other species, a number of amino acid sequences were found in MYB family transcription factor proteins, and therefore it was hypothesized that these amino acid sequences might be MYB family transcription factors conserved amino acid sequences. As shown in the Figure 4 , amino acid sequences such as KGPW**EED, GP**W, K*CR*RW*N*L*P*I, T**EE, GN*WA and RTDN*IKN*WN***KKK are conserved amino acid sequences of MYB family transcription factors ( Figure 4 ). To investigate the phylogenetic and evolutionary relationships of MYB family transcription factors in different species, we constructed phylogenetic trees of the amino acid sequences of some MYB family transcription factors in Arabidopsis thaliana, Oryza sativa and Glycine max Panicum virgatum, Phragmites australis and Sorghum bicolor. using MEGA 11.0 software (Tamura et al., 2021). Among them, we found that GmMYB187 and GmMYB306 were highly related, GmMYB392 and GmMYB60 were highly related, AtMYB94 and AtMYB96 were highly related, OsMYB36a, OsMYB36b and OsMYB30 were highly related, which indicated that the MYB family of transcription factors were highly related in various species have close affinities between them. At the same time, we also found that MYB transcription factors between different species have strong phylogenetic relationships. Such as, AtMYB94 and GmMYB60 were highly related, AtMYB60 and OsMYB4P were highly related, AtMYB3R-5, GmMYB3R-1 isoform X1 and OsMYB3R2-L were highly related, it is possible that WRKY family transcription factors have similar functions in different species. MYB transcription factors are involved in regulating plant growth and development, secondary metabolism, and response to environmental stress ( Supplementary Figure S1 ).

MYB transcription factors have a conserved DNA binding domain in their structure. These transcription factors are composed of three conserved functional domains, a DNA binding domain (DBD), a transcription activation domain (TAD) and an incompletely defined negative regulatory domain (NRD) (Thompson and Ramsay, 1995). Ogata et al. believe that R2 and R3 are necessary for MYB transcription factor to recognize DNA sequences, and the C-terminal helix of R3 subunit can specifically bind to the core sequence in the cis acting element (Ogata et al., 1995). The cis acting elements that can be recognized by MYB transcription factors are called MBS (MYB-binding sites), which are generally rich in adenine and cytosine residues, such as (T/C)AAC(G/T) G(A/C/T)(A/C/T), (C/T)NGTT(A/G), ACC(A/T)A(A/C)(T/C), ACC (A/T)(A/C/T)(A/C/T) (Prouse and Campbell, 2012).

The sequence (T/C)AAC(G/T)G(A/C/T)(A/C/T) widely exists in the promoters of various stress response genes. Shukla et al. found that SbMYB44 can combine with the TAACTG motif on the promoters of many stress response genes to activate the expression of related genes (Shukla et al., 2015). Yang et al. found that OsMYB5P can regulate gene transcription and expression by recognizing and combining the CAACTG motif on the downstream target gene OsPT5 promoter (Yang et al., 2018).

MYB transcription factors can also bind to the (C/T)NGTT(A/G) sequence and participate in regulating the biosynthesis of certain secondary metabolites. Zhou et al. found that FtMYB11 can directly bind to the AATAGTT sequence in its target gene promoter region, inhibiting the biosynthesis of phenylpropanoids in Fagopyrum tataricum (Zhou et al., 2017).

The sequence ACC(A/T)A(A/C)(T/C) and ACC(A/T)(A/C/T)(A/C/T) are known as AC-box, in which ACC is the core identification sequence. Studies have shown that both PtMYB4 and EgMYB2 can bind to AC-box to regulate the biosynthesis of lignin (Patzlaff et al., 2003). In addition, some MYB transcription factors in plants can also interact with E-box (CANNTG) and I-box (GATAAG). For example, LeMYBI can bind with I-box (Rose et al., 1999). BplMYB46 can bind with E-box (CANNTG), TC box (T(G/A)TCG (C/G)) and GT box (A(G/T)T(A/C)GT(T/G)C) (Guo et al., 2018).

MYB mainly activates or inhibits transcription by directly binding to specific DNA sequences in downstream target gene promoter regions. AtMYB73 directly binds to the promoter region of the actin depolymerizing factors (ADF) gene, inhibiting its expression and hindering actin depolymerization in Arabidopsis thaliana, thereby altering the composition of the plant cytoskeleton (Wang et al., 2021c). Zhou et al. Identified that the CgMYB1 transcription factors, a member of the R2R3-MYB TF family. The CgMYB1 transcription factors gene is induced by salt and cold stresses. Overexpression of CgMYB1 in Arabidopsis significantly enhanced salt and cold tolerance. The interaction between CgMYB1 and the promoter of CgbHLH001, followed by the activation of the downstream stress-responsive genes, mediates the stress tolerance and improves the survival under salt and cold stress (Zhou et al., 2023b). Overexpression of the REVEILLE-8-type transcription factor CstMYB1R1 in Crocus floral was explored for its possible role in regulating crocus flavonoid and anthocyanin biosynthetic pathway. The yeast one-hybrid technique was used to verify that CstMYB1R1 interacts with the promoter of the LDOX gene to directly regulate its transcription. The expression of CstMYB1R1 significantly increased the levels of flavonoids and anthocyanins in Nicotiana tabacum and improved the abiotic stress tolerance of the plants (Bhat et al., 2023). Du et al. Identified that the N-terminal domain of MYB transcription factor MdMYB108L, which was significantly induced under salt stress, as transcriptionally active. Overexpression of MdMYB108L increased the germination rate, the length of the primary root and the antioxidant activities of catalase and peroxidase in transgenic Arabidopsis seeds and reduced the accumulation of reactive oxygen species (ROS). The overexpression of MdMYB108L also increased the photosynthetic capacity of the hairy root tissue (leaves) under salt stress. MdMYB108L was capable of binding to the MdNHX1 promoter and positively regulating the transcription of the apple salt tolerance gene MdNHX1, thereby enhancing the salt tolerance of the transgenic plants (Du et al., 2022). According to the review, MYB transcription factor directly binds to the cis acting elements in the promoter regions of downstream target genes, regulates their transcription levels, and thereby regulates plant growth and development as well as transmits environmental signals.

Furthermore, the binding of MYB transcription factor to downstream target gene promoter sequences is also influenced by upstream protein interactions, thereby regulating changes in plant phenotype. Under ultraviolet radiation, AtMYB73/77 interacts with photoreceptors, inhibiting the binding activity of MYB73/77 to downstream auxin responsive target genes and negatively regulating hypocotyl elongation and lateral root development in Arabidopsis thaliana (Yang et al., 2020c). The N-terminus of the R3 repeat sequence of the MYB transcription factor contains a bHLH structural domain that binds to bHLH and WD40 to form the MBW complex, and flavonoid MYB deterrents are able to bind to basic helix-loop-helix factors and disrupt the MBW complex. For example, AtMYB75/90/113 associates with bHLHs (GL3, EGL3 and TT8) and WD40 (TTG1) to form the MBW complex in Arabidopsis, which controls the expression of the downstream anthocyanin late biosynthetic genes LDOX and DFR (Ma et al., 2019; Zheng et al., 2019). Li et al. found the expression patterns of FhPAP1 in Freesia hybrida and the late synthesis genes involved in anthocyanin synthesis are similar. FhPAP1 can not only activate the expression of structural genes in the anthocyanin synthesis pathway, but also activate endogenous bHLH2 transcription factor genes in plants, such as FhTT8L in Freesia hybrida, AtTT8 in Arabidopsis, and NtAN1 in Nicotiana tabacum. In addition, FhPAP1 can also interact with bHLH transcription factor FhTT8L and WD40 protein FhTTG1 to form MBW complexes (Li et al., 2020d). Li et al. discovered that FhMYB27 and FhMYBx have different regulatory mechanisms: FhMYB27 mainly interacts with the MBW complex member FhTT8L, and then binds to the MBW complex in the form of a cofactor. By utilizing its strong transcriptional inhibitory activity, it transforms the MBW complex that originally had a positive regulatory effect into an MBW complex with inhibitory activity, thereby inhibiting the expression of downstream genes (Li et al., 2020e). Members of the MYB family can also bind to each other to form multimers. Such as, BplMYB46 can heterodimerize with BplMYB6, 8, 11, 12 and 13 to enhance binding to downstream target genes in Betula platyphylla. When BplMYB46 and BplMYB13 were coexpressed, the heterodimer formed by them enhanced the ROS scavenging ability by increasing the transcription of downstream genes encoding superoxide dismutase (SOD), POD and glutathione sulfotransferase (Wang et al., 2019b). Thus, MYB transcription factors can activate or repress downstream gene expression after interacting with upstream factors, thereby influencing downstream gene expression and regulating plant tolerance to abiotic stress.

Water is required for plant growth and development, and drought causes increased evaporation of water from plants, decreases soil water availability, and interferes with water transport processes in plants, resulting in irreversible damage to plants such as wilting of canopy leaves, branch dieback, and even death of the entire plant. The physiological mechanisms underlying drought-induced plant death are now the focus of intense research (Huang et al., 2021a; Vadez et al., 2024; Huang et al., 2021b; Chieb and Gachomo, 2023). Zhang et al. found that ZmMYB-CC10 improves drought tolerance in maize by reducing oxidative damage. ZmMYB-CC10 increases APX activity and decreases H₂O₂ levels. ZmMYB-CC10 was also shown to activate the expression of ZmAPX4 by binding directly to its promoter using yeast one-hybrid crosses and luciferase assays (Zhang et al., 2022a). CaDIM1 was identified by Lim et al. CaDIM1 has an N-terminal MYB structural domain and a C-terminal acidic domain, which are responsible for recognizing and activating target genes, respectively. CaDIM1-silenced plants exhibited ABA-insensitive and drought-sensitive phenotypes as well as reduced expression of adversity-responsive genes (Lim et al., 2022). The R2R3 MYB transcription factor MYB44-5A in Triticum aestivum L. was identified by Peng et al. The overexpression of TaMYB44-5A reduced the tolerance to drought and the sensitivity of transgenic Arabidopsis thaliana to ABA. At the same time, TaMYB44-5A down-regulated the expression levels of drought- and ABA-responsive genes, and TaMYB44-5A bound directly to the MYB binding site on the promoter and repressed the transcription level of TaRD22-3A (Peng et al., 2024). MYB transcription factor PtrMYB94 involved in drought response and ABA signaling in Populus trichocarpa, was identified by Fang et al. The overexpression of PtrMYB94 improved the drought response of the plants. Seed germination was inhibited and ABA levels were significantly increased in overexpressing PtrMYB94 plants. Overexpression of PtrMYB94 plants also up-regulated the transcript levels of some ABA and drought-responsive genes ABA1 and DREB2 (Fang et al., 2020).

The visible symptoms of salt damage are the greening of the leaf tips, followed by the scorching, browning and death of the leaves. The result is stunted plant growth, poor root development, sterility and a reduction in the production of seeds. Salinity can cause soil crusting, poor soil structure, easy autodispersion of soil particles after irrigation and crusting, which in turn prevents water infiltration and reduces the soil’s water-holding capacity. This leads to reduced soil aeration and water conductivity, which severely affects plant growth and development and results in reduced yields (Zhou et al., 2024a, 2024b; Zhang et al., 2024a; Kausar and Komatsu, 2022; Xiao and Zhou, 2023). The MYB transcription factor MYB148 has been implicated in salt stress responses by Park et al. Salt and drought treatments increased PagMYB148 expression in hybrid Populus alba x P. glutulosa. However, pagmyb148 knockout plants exhibited a more sensitive phenotype under salt stress than wild-type plants. The chlorophyll content of the pagmyb148 knockout plants was lower than that of the wild type under salt stress. The expression of genes involved in the salt stress response was higher in the pagmyb148 knockout plants than in the wild type (Park et al., 2024). Wang et al. Identified SaR2R3-MYB15 transcriptional activity and nuclear localization. The overexpression of SaR2R3-MYB15 increased the activity of antioxidant enzymes and the accumulation of proline, but decreased the level of malondialdehyde (MDA), which means that they have the potential to improve salt tolerance (Wang et al., 2024a). A total of 210 MYB transcription factor SbMYB1- SbMYB210 were identified by Lu et al. SbMYBAS1 (SbMYB119) was found to be downregulated under salt stress conditions. Overexpression of SbMYBAS1 in Arabidopsis plants had a significantly lower dry weight and chlorophyll content than the wild type under salt stress conditions, but a significantly higher membrane permeability, MDA content and Na⁺/K⁺ ratio than the wild type. Results also showed that SbMYBAS1 is capable of regulating expression of AtGSTU17, AtGSTU16, AtP5CS2, AtUGT88A1, AtUGT85A2, AtOPR2 and AtPCR2 under salt stress conditions (Lu et al., 2023). These results indicate that MYBs also play an important role in plant response to salt stress.

Temperature is a key factor in plant growth and development. Temperature affects plant growth and ultimately crop yield, along with factors such as light, carbon dioxide, humidity, water and nutrient levels. Plants grow best when the temperature is kept just right for them to be able to grow. With both positive and negative effects, the higher the temperature, the faster most biological processes take place. For example, in most cases this can lead to a faster rate of growth and an increase in the yield of fruit crops (Huang et al., 2023; Wen et al., 2024; Islam et al., 2024).

Nitrogen (N), Phosphorus (P) and Potassium (K), which are essential plant nutrients, play extremely important physiological roles in helping plants grow and development (Kumar et al., 2021).

N is a component of the vitamin system and the energy system of the plant. The element nourishes leaves and helps branches, stalks, and stems (Antenozio et al., 2024). Cereal (Setaria italica) native to China, that is highly tolerant to low nutrient stress. Ge et al. systematically analyzed the cereal transcriptome under low nitrogen stress. There were 74 transcription factor genes in the differentially expressed genes (DEG), including 25 MYB-like transcription factors. Root development in Arabidopsis and overexpressing SiMYB3 in Oryza sativa under low nitrogen stress was superior to that of the wild type. SiMYB3 could specifically bind to the MYB element in the promoter region of the TAR2 promoter region of the growth hormone synthesis-related genes conserved in Oryza sativa and Setaria italica. SiMYB3 can regulate root development under low nitrogen conditions by regulating growth hormone synthesis in plant roots (Ge et al., 2019). Wang et al. identified all MYB genes in Phaeodactylum tricornutum, and analyzed the MYB transcription factor gene family at the genome level. The homology analysis of the MYB transcription factor genes indicated that PtMYB3, PtMYB15 and PtMYB21 can play important roles in regulating the circadian rhythm and response to nitrogen stress in Phaeodactylum tricornutum (Wang et al., 2022b).

P determines the differentiation of flower buds, the development of pollen key elements, is the reproductive growth and nutritional growth of essential elements. At the same time, phosphorus is involved in various metabolisms in the body, including carbohydrate metabolism, promotion of nitrogen metabolism, and fat metabolism (Prathap et al., 2022). Plants take up phosphate from the soil mainly through phosphate transporter proteins (mainly PHT1 family proteins) in the root system and transport phosphate to the aboveground via transporter proteins such as PHO1 (Gu et al., 2016). PHR transcription factors, as MYB family transcription factors, can positively regulate the phosphorus deficiency response in plants, and it binds to the P1BS motif in the promoter region of phosphorus deficiency response genes, thus activating the expression of downstream genes. SPX proteins, as phosphorus receptors, can avoid toxicity caused by phosphorus over-accumulation by interacting with PHR1 (Arabidopsis) or PHR2 (Oryza sativa), and inhibiting their transcriptional activities under normal conditions, while SPX proteins do not affect PHR transcriptional activities when plants are in low phosphorus environments (Wang et al., 2014). It has been shown that SPX proteins do not directly sense phosphate, but instead sense soluble inositol polyphosphates (InsPs) (Wild et al., 2016). Inositol pyrophosphate InsP8 acts as an intracellular phosphate signaling substance to regulate phosphorus homeostasis by modulating the interaction of SPX1 with PHR1 (Dong et al., 2019). Arabidopsis thaliana accumulates InsP8 under phosphorus-sufficient conditions and promotes the binding of the InsP8-SPX complex to the CC structural domain of the PHR transcription factor, thereby repressing PHR-mediated phosphorus-deficiency-responsive gene expression ( Figures 6A, B ) (Ried et al., 2021). The microRNA399 can play a key role in phosphorus homeostasis and phosphorus deficiency response through post-transcriptional regulation. MicroRNA399 is induced to be expressed under phosphorus deficiency conditions and positively regulated by PHR1, which promotes phosphorus uptake and transport by inhibiting the mRNA expression of its target gene, the ubiquitin-conjugating E2 enzyme PHO2, and then increasing protein expression of PHO1 and PHT1 in the downstream of PHO2 (Liu et al., 2012; Xiao et al., 2022b). MiR399-PHO2 regulatory module also plays a similar role in other plants. For example, miR399 is specifically induced by low phosphorus stress in maize, and overexpression of miR399b causes maize to overexploit phosphate in the shoot and develop symptoms of phosphorus toxicity (Du et al., 2018) ( Figure 6B ). Interestingly, miR399 also negatively regulates the expression of phosphate transport proteins ZmPHT1;1, ZmPHT1;3 and ZmPHT1;13 in maize, and this regulation is modulated by the long-chain non-coding RNA PILNCR2. Meanwhile, PILNCR2 is induced by phosphorus deficiency and forms RNA/RNA dimers with ZmPHTs, thus interfering with the targeting of miR399 to ZmPHTs (Wang et al., 2023b).

The main function of K is to participate in plant metabolism, such as promoting photosynthesis and the transfer of photosynthesis products, regulating ion and water balance, promoting protein metabolism, and enhancing plant resistance (Mulet et al., 2023; Xiao et al., 2022a). Niu et al. found that RsMYB39 and RsMYB82 appeared to be non-canonical MYB anthocyanin activators and deterrents, respectively. It was confirmed that RsMYB39 strongly induced the promoter activity of the anthocyanin transport-related gene RsGSTF12, whereas RsMYB82 significantly reduced the expression of the anthocyanin biosynthesis gene RsANS1. Their data demonstrate the strong effect of potassium on sugar metabolism and signal transduction and its regulation of anthocyanin accumulation through different sugar signals and R2R3-MYB in a hierarchical regulatory system (Niu et al., 2023). These results indicate that MYB regulates the ability of plants to maintain normal growth and development under nutrient deficient conditions by enhancing the absorption capacity of plant roots for nutrients.

Excessive amounts of heavy metals inhibit seed germination and seedling growth, damage antioxidant enzyme systems and membrane systems, and induce chromosomal aberrations. Appropriate metals can promote plant growth, but excessive heavy metals can form a greater toxicity to cells and affect plant growth and development (Zhang and Lu, 2024b; Liu et al., 2024a; Gu et al., 2016). Excessive cadmium (Cd) in soil poses a serious hazard to the survival and development of a wide range of organisms. Feng et al. identified a MYB family transcription factors PsMYB62 in Potentilla sericea. Net photosynthetic rate, stomatal conductance, transpiration rate, intercellular CO₂ concentration, and chlorophyll content of PsMYB62 overexpressing plants were significantly higher than that of the control after Cd treatment. The expression of NtHMA3, NtYSL, NtPDR4 and NtPDR5B in the transgenic lines was significantly lower than that of the control, while the expression of NtNAS3, NtSOD and NtGSH2 was significantly higher than that of the control (Feng et al., 2024). Daucus carota is a globally important root vegetable crop, and it has evolved multiple transcriptional regulatory mechanisms to cope with Cd stress. Sun et al. found that the expression level of DcMYB62 was positively correlated with the accumulation pattern of carotenoids, and that the expression of DcMYB62 improved Cd tolerance in Arabidopsis by increasing seed germination, root length, and overall survival. Heterologous expression of DcMYB62 increased the transcription of genes associated with heavy metal resistance in Arabidopsis, particularly nicotinamide synthase (Sun et al., 2024). These results indicate that MYB also plays an important role in plant response to heavy metal stress.

Glucosinolate (GSL) is widely known as a secondary plant metabolite derived from amino acids and sugars. It functions not only as a protection against pests, but also helps plants to resist various diseases (Patil et al., 2024). Augustine et al. identified four MYB28 homologues BjMYB28-1, BjMYB28-2, BjMYB28-3, BjMYB28–4 from polyploid mustard (Brassica juncea), and phylogenetic analyses indicated that the four BjMYB28s proteins evolved through a process of hybridization and replication. The four BjMYB28s genes all encode functional MYB28 proteins and are involved in the synthesis of glucosinolates (Augustine et al., 2013). Seo et al. found in turnip (B. rapa) that the expression of some BrMYBs genes BrMYB28, BrMYB34, and BrMYB51 are also increased under abiotic and biotic stress conditions. In addition, the function of three BrMYB28s transcription factor protein involved in the regulation of lipid, indole and aromatic GSL synthesis, respectively, as well as the expression of synthetic genes BrAOP2 and BrGSL-OH in transgenic B. rapa was analyzed by Agrobacterium transformation (Seo et al., 2016). In addition, researchers have found that MYB transcription factor MYB28, MYB29 and MYB76 specific activation is involved in GSL synthesis. MYB transcription factor binding sites exist in the promoters of GSL biosynthetic genes, and MYB transcription factor can directly activate their expression (Hirai et al., 2007; Sønderby et al., 2010).

Flavonoids are important secondary metabolites in plants, and anthocyanins, flavonols, and isoflavones are important components of them. As a class of multifunctional compounds, they include regulation of plant cell wall formation, resistance to UV-B damage and defense against diseases (Xu et al., 2014). However, the synthesis pathways of flavonoids are relatively numerous and complex, so we have briefly summarized a flowchart for a better understanding of flavonoid biosynthesis pathways ( Figure 7 ). In addition to being regulated by enzymes involved in the synthetic pathway, the metabolic pathway is also regulated by the MYB family of transcription factors. By binding to structural genes in the plant body, MYB transcription factors are able to activate multiple related genes in the plant’s secondary metabolic synthesis pathway, causing them to be expressed synergistically, thereby initiating secondary metabolism in the plant.

Flavonoids have a wide variety of pharmacological activities and physiological functions, this has led to the widespread interest in this group of compounds, which is now the focus of research. Anthocyanins are a class of water-soluble pigments found widely in plants and determine the color of plant flowers, leaves, fruits, stems and seed coat. Anthocyanins also contribute to several physiological and biochemical processes, including attraction of insects for pollination, UV prevention, and stress protection in plants (Ahmed et al., 2015; Oh et al., 2011). Anthocyanin biosynthesis is transcriptionally regulated by the MYB-bHLH-WD (MBW) triad, and several MYB transcription factor proteins related to anthocyanin synthesis have been identified in plants, such as Myrica rubra, where MrMYB1 interacts with MrWD40–1 and MrbHLH1, to form the MBW complex that regulates anthocyanin accumulation (Niu et al., 2010). In Populus, PtrMYB57 can interact with bHLH131 and PtrTTG1 to negatively regulate anthocyanin biosynthesis (Wan et al., 2017). Other genes that perform similar functions include VvMYBC2L2 in Vitis vinifera (Zhu et al., 2018), CmMYB7 and CmMYB6 in Chrysanthemum morifolium (Xiang et al., 2019). Feng et al. cloned the R2R3-MYB transcription factor AgMYB2 from Apium graveolens L., and heterologous expression of AgMYB2 in Arabidopsis thaliana produced more anthocyanins and dark purple leaves and flowers. And a yeast two-hybrid assay experiment demonstrated the interaction between AgMYB2 and bHLH transcription factor proteins (Feng et al., 2018). Jiang et al. found an R2R3 MYB transcription factor, ThMYB14 in T. hemsleyanum. The overexpression MYB14 or knockout of myb14 lines significantly promoted or inhibited the accumulation of flavonoids, respectively. Promoter sequence analysis identified many potential MYB binding sites, including CCAAT box, MBS and MBSI elements upstream of flavonoid biosynthesis related genes. ThMYB14 promotes flavonoid accumulation by specifically recognizing AAC elements in these sites. In conclusion, ThMYB14 can regulate the accumulation of flavonoids in T. hemsleyanum (Jiang et al., 2025). Xu et al. identified a total of 26 R2R3-MYB TF in T. hemsleyanum, most of which were clustered into functional branches of abiotic stress. Through protein-protein interaction prediction, ThMYB4 and ThMYB7 related to flavonoid biosynthesis were screened out. ThMYB4 and ThMYB7 were positively correlated with genes of flavonoid biosynthesis pathway in T. hemsleyanum. The expression of ThCHS and ThCHI were significantly increased in hairy roots with overexpression of ThMYB4 and ThMYB7 lines, suggesting that ThMYB4 and ThMYB7 can act as regulators in flavonoid biosynthesis (Xu et al., 2023).

Flavonols are important flavonoids whose synthesis from dihydroflavonols is catalyzed by flavonol synthase (FLS). In Arabidopsis, AtMYB11, AtMYB12, and AtMYB111 are all able to independently activate the gene encoding chalcone synthase (CHS), and chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), and flavonol synthase (FLS) together determine flavonol content (Luo et al., 2008; Misra et al., 2010; Pandey et al., 2012). Matsui et al. identified a MYB transcription factor protein, FeMYBF1, from Fagopyrum esculentum Moench and performed amino acid sequence analysis and phylogenetic analyses, which indicated that expression of FeMYBF1 in the flavonol-deficient Arabidopsis triple mutant, myb11/myb12/myb111, promotes flavonol synthesis. Expression of FeMYBF1 driven by the CaMV 35S promoter in Arabidopsis resulted in up-regulation of AtFLS1 expression and over-accumulation of flavonol glycosides (Matsui et al., 2018). The MYB transcription factor GtMYBP3 and GtMYBP4 in Gentiana triflora similarly activate the expression of flavonol synthesis genes and increase flavonol content when heterologously expressed in Arabidopsis (Nakatsuka et al., 2012). There are also some MYB transcription factors in other species, such as in Pyrus betulifolia PbMYB12b, in Malus domestica MdMYB22 can positively regulate flavonol biosynthesis (Zhai et al., 2019; Wang et al., 2017b). In Glycine max GmMYB176 regulates isoflavonoid biosynthesis by activating the expression of soybean chalcone synthase gene (Anguraj Vadivel et al., 2019). Isoflavonoids are a class of flavonoids found mainly in the Pteridophyceae family, which accumulate in the immature embryo of Glycine max. R1-MYB GmMYB176 is also involved in the regulation of CHS expression and isoflavone synthesis. Mutant myb176 silencing leads to a decrease in the accumulation of isoflavonoids in hairy roots (Yi et al., 2010).

Terpenoids are the most abundant class of plant natural products due to their extensive use in flavor, cosmetics, pharmaceuticals, agriculture and chemical industries. Therefore, there is a very broad development and application prospect (Bouvier et al., 2005). Reddy et al. identified the PGT-specific R2R3-MYB gene MsMYB in Mentha spicata Linn. RNA-Seq data and functionally characterized it. To analysis of MsMYB-RNAi transgene lines showed an increase in monoterpene levels and MsMYB overexpression lines showed a decrease in monoterpene levels. The results suggest that MsMYB is a novel negative regulator of monoterpene biosynthesis. The study on the regulation of terpene metabolism by MYB transcription factors is still in the preliminary stage, and this is also the first report on the regulation of monoterpene synthesis by R2R3 MYB (Reddy et al., 2017).

Lignin is one of the main components that make up the secondary walls of lignocells and fibers, which are synthesized via the phenylpropane pathway and are the main components that make up phytochelatins, which resistance to UV-B damage and pathogen attack (Boerjan et al., 2003). Three MYB transcription factors in Arabidopsis, AtMYB20, AtMYB42 and AtMYB43, activate lignin synthesis-related genes and mediate secondary wall formation, and silencing of these genes resulted in a significant reduction in lignin synthesis in Arabidopsis and led to defects in plant growth and development (Geng et al., 2020). CsMYB330 and CsMYB308 in Citrus sinensis have opposite regulatory effects, with the former activating and the latter inhibiting the lignification process (Jia et al., 2018). In Eucalyptus EgMYB1 specifically interacts with the histone variant EgH1.3, which strongly inhibits lignin deposition in the xylem cell wall. Thus preventing premature or inappropriate lignification of secondary walls (Soler et al., 2017). In addition, MuMYB31 also inhibits lignin synthesis in Musa nana (Tak et al., 2017). There are a number of other species with MYB family transcription factors that are also capable of regulating lignin synthesis, for example ZmMYB31, ZmMYB42 in Zea mays, PvMYB4a in Panicumvirgatum, LlMYB1 in Leucaena leucocephala and CmMYB1 in Chrysanthemum morifolium are able to inhibit lignin synthesis (Fornalé et al., 2010; Shen et al., 2012; Omer et al., 2013; Zhu et al., 2013).

Astragaloids compounds are low in normal tissues of the plant kingdom, and mono- and di-phenolic hydroxylated astragalus compounds are found mainly in the thin-walled cells of the xylem of plant tissues. When plants are infected by pathogens or externally stimulated, the total content of astragaloids in the stimulated tissue sites increases significantly. Therefore, natural astragaloids can be stress products of plants (Liang et al., 2023). Expression of AtMYB14 and AtMYB15 in grape trichome roots induces genes encoding stilbene synthases and leads to accumulation of glycosylated stilbenes (Höll et al., 2013). In Solanum lycopersicum epidermal trichome regulators Woolly and SlMYB31 are synergistically used in the biosynthesis of tomato cuticle waxes by regulating the expression of SlCER6 (Xiong et al., 2020). In Capsicum annuum CaMYB31 can be a master regulator of capsaicinoid synthesis genes (Han et al., 2019). In Salvia miltiorrhiza SmMYB98 can regulate the biosynthesis of tanshinone and salvinorin in hairy roots (Hao et al., 2020). Thus the major regulatory role of MYB transcription factors in plant secondary metabolic processes can regulate the synthesis of a wide range of secondary metabolites.

Some studies have found that MYB transcription factors regulate the synthesis of terpenoids mainly by directly regulating the transcriptional expression of structural genes in the terpenoid synthesis pathway. MYB transcription factors can positively regulate the expression of terpenoid synthesis pathway enzyme genes, thereby promoting the biosynthesis of terpenoids. Matías et al. found overexpressing AaMYB1in Artemisia annua can activate key enzymes in the artemisinin biosynthesis pathway, such as sophoride oxidase (CYP71AV1), sophoride synthase (ADS), farnesyl diphosphate synthase (FDS), artemisinin aldehydeΔ11 (13) reductase (DBR2), and aldehyde dehydrogenase (ALDH1) encoding genes, thereby increasing artemisinin synthesis. AaMYB1 activates the expression of enzymes GA3ox1 and GA3ox2 in the GA biosynthesis pathway, increasing GA synthesis and promoting the development of Artemisia annua glandular hairs. The density of glandular hairs is positively correlated with artemisinin content (Matías-Hernández et al., 2017). Although MYB transcription factor can positively regulate the biosynthesis of artemisinin, the mechanism is different. For example, MYB transcription factor AaBPF1 promotes the expression of enzyme genes of artemisinin biosynthesis pathway in Artemisia annua, while AaMIXTA1 increases the artemisinin content in Artemisia annua by increasing the growth density of glandular hairs (Ma et al., 2019; Shi et al., 2018). SmMYB98 plays a positive regulatory role in the biosynthesis of tanshinone and salvianolic acid in Salvia miltiorrhiza. SmMYB98 can directly bind to the promoters of the key enzyme genes (SmGGPPS1) in the terpene biosynthesis pathway and encoding phenylalanine ammonia lyase (SmPAL1) and encoding rosmarinic acid synthase (SmRAS1) in the phenolic acid biosynthesis pathway, directly regulate their expression levels and promote the synthesis of tanshinone and salvianolic acid (Hao et al., 2020).

In addition, MYB transcription factors can also negatively regulate the expression of terpenoid synthesis pathway enzyme genes, affecting the biosynthesis of terpenoid compounds. Reddy et al. found MsMYB can inhibit the expression of geranyl diphosphate synthase gene GPPS in Mentha spicata, thereby reducing the accumulation of its catalytic product GPP in vivo and the reduction of monoterpene biosynthetic precursor GPP, which hinders the biosynthesis of limonene, carvone and other monoterpene substances (Reddy et al., 2017).

Some studies have found that MYB can not only play a regulatory role alone, but also form protein complexes with other transcription factors to participate in the regulation of secondary metabolic biosynthesis. FhMYB21L1 and FhMYB21L2 can significantly activate the expression of monoterpene synthase gene FhTPS1 and promote the synthesis of linalool in Freesia hybrida. When FhMYC2 interacts with FhMYB21L2 to form a protein complex, it interferes with the binding of FhTPS1 promoter, inhibits the expression of FhTPS1 and inhibits the synthesis of linalool. The heterologous expression of FhMYC2 and FhMYB21L2 can also inhibit the expression of terpene synthase gene AtTPS14 in Arabidopsis thaliana. This study demonstrated that MYB- bHLH protein complex was involved in the regulation of plant monoterpene biosynthesis (Yang et al., 2020b). TmMYB39 can interact with TmbHLH13 to form a TmMYB39-TmbHLH13 complex in Taxus madia, and significantly activate the expression of taxol biosynthesis genes GGPPS and T46OH, promoting the synthesis of taxol in Taxus media (Yu et al., 2022).

MYB transcription factors not only regulate terpene synthesis by forming complexes with other proteins, but also form hierarchical transcriptional regulation with other transcription factors. In Artemisia annua, the HD-Zip family proteins AaHD1 and AaHD8 directly activate the expression of MYB transcription factor AaTAR2, which can activate the expression of artemisinin biosynthesis pathway enzyme genes ADS, CYP71AV1, DBR2 and ALDH1. Finally, AaTAR2 and HD-Zip synergistically promote the biosynthesis of artemisinin in Artemisia annua (Zhou et al., 2020).