It has long been recognized that temperature is the primary environmental factor influencing the composition of seed oil fatty acids of different crops (Canvin, 1965), affecting the final seed oil quality. Seeds are not only the harvest organ for industrial use, but also a reserve and perpetuation organ of the species (Izquierdo et al., 2017), whose oil is consumed by humans or used as a sub-product for biofuel. Literature documents the responses of fatty acids to minimum temperature during grain filling of seeds across various crops as well as different genotypes of these crops (Aguirrezábal et al., 2009, 2015 and references therein). However, this fragmented information reveals significant variability in the response of oil fatty acids to minimum temperature during seed filling, both among and within species and genotypes (Zanetti et al., 2022; Brandán et al., 2022; Abou Chehade et al., 2022; Angeloni et al., 2017; Baux et al., 2013; Zuil et al., 2012). Thus, a model encompassing common responses of fatty acids to minimum temperature from seed oils across a wide range of species and genotypes has not yet been established.

The absence of such a model likely stems from experimental challenges, including: i) conducting simultaneous experiments with species of diverse life forms and architectural traits; ii) synchronizing the grain filling period among species and genotypes that vary in their thermal and photoperiodic requirements for development, as well as their thermal and radiation needs for growth; iii) integrating results obtained under controlled conditions with those from field studies. Combining data from plants cultivated under both conditions is contentious due to significant abiotic factors that alter the growing environment (see Poorter et al., 2012, 2016 and references therein).

Given these difficulties, conducting experiments with a broad array of genotypes and species in field conditions, under varying minimum temperatures during grain filling [e.g., across multiple locations, latitudes, sowing dates, or by manipulating temperatures in the same field (Izquierdo et al., 2002; García-Inza et al., 2014, 2018)], is difficult. Similarly, adjusting temperatures during grain filling in growth chambers or greenhouses (Izquierdo et al., 2006, 2008) requires extensive experimental efforts and significant human and technical resources. These efforts are still necessary to concurrently cultivate numerous genotypes of different species, particularly when utilizing large-scale phenotyping facilities (e.g., Minervini et al., 2017).

The high intraspecific variability in the response of seed oil fatty acid composition to temperature may be attributed to natural variation and genetic enhancement. Various genotypes of multiple oil-producing species, which exhibit high percentages of specific fatty acids, have been developed for a range of applications. For example, high oleic (HO) genotypes have been developed in several species, significantly increasing the oleic acid content compared to traditional genotypes. E.g., sunflower (Soldatov, 1976): ~75% vs ~35%; rapeseed (Alberio, 2017): ~81% vs ~60%; soybean (Kinney and Knowlton, 1998): ~84% vs ~17%; maize (Beló et al., 2008): ~39% vs ~25%; safflower (Zemour et al., 2021; Zanetti et al., 2022): ~75% vs ~12%. It is generally accepted that the response of fatty acids to minimum temperature in HO genotypes is lower compared to traditional (wild type, WT) genotypes (Zuil et al., 2012; Alberio et al., 2016; Alberio, 2017, unpublished data). However, some studies report similar responses between certain HO genotypes and WT genotypes (Angeloni et al., 2017; Izquierdo et al., 2009). Furthermore, the response of oil fatty acids to minimum temperature can be modified by the genetic background in which HO mutations are present (Alberio et al., 2018).

Conversely, genotypes with mutations other than HO have also been obtained in several species [e.g., high stearic (Fernández-Moyá et al., 2002) and low linolenic (Deng and Scarth, 1998)]. Additionally, genotypes combining mutations in two genes of the fatty acid synthesis pathways, coding for different fatty acids, have been developed. These genotypes enhance the percentage of two fatty acids in the seed oil [e.g., high palmitic/high linoleic in sunflower (Osorio et al., 1995), high palmitic/high oleic in sunflower (Fernández-Martínez et al., 1997), high oleic/low linolenic in rapeseed (Scarth and McVetty, 1999)]. The response of fatty acids to minimum temperature in genotypes carrying these traits or their combinations is not well understood (Izquierdo et al., 2013). It remains unclear whether these traits affect the responses of other fatty acids that are not directly influenced by these mutations (e.g., upstream or downstream in the synthesis pathway).

Meta-analytical approaches can be employed to combine results from various studies and unpublished data into comprehensive response models (e.g., Poorter et al., 2010). These approaches provide insights into the phenotypic plasticity [i.e., a plant’s ability to respond to changes in resource availability (Bradshaw, 1965)] across a range of genotypes. Meta-analysis has not been previously applied to explore common response patterns of fatty acids to temperature across numerous species and genotypes within species. This approach could be instrumental in dealing the high intraspecific variability in the percentage of the same fatty acid among species and even among genotypes within the same species.

Therefore, the aim of this study was to investigate common responses of seed oil fatty acids to minimum temperature during grain filling across species and genotypes. This was achieved by conducting meta-analysis using a purpose-built database comprising a wide set of genotypes from nine species grown under varied environmental conditions. To achieve this objective, we first established a General Model by identifying common responses of main seed oil fatty acids to minimum temperature during grain filling in genotypes of four widely cultivated crop species (sunflower, soybean, rapeseed and maize). By selecting appropriate datasets, specific responses were identified: i) interspecific responses of different fatty acids to minimum temperature during grain filling within these four species, ii) effects of the HO trait on these responses, and iii) behavior of fatty acids when cultivating plants in the field or under controlled conditions in pots. Finally, we assessed the scope of the established models using independent data of: iv) genotypes carrying mutations other than HO in the oil fatty acid synthesis pathway, and v) species whose responses of fatty acids to temperature have been less investigated in prior research.

Common patterns of fatty acid responses to temperature were identified across a broad spectrum of genotypes from nine species using a previously unavailable database ( Tables 1 – 3 ; Repository). This database exhibits significant genotypic variation in various traits: i) plant morphology and architecture (e.g., from herbs to trees, branched and unbranched species, genotypes with determinate and indeterminate growth, planophiles, extremophiles, and erectophiles), ii) fruit types (achenes, pods, siliques, fleshy, gourds, cypselae), iii) plant physiology (e.g., autotrophic and heterotrophic fruits, C3 and C4 photosynthetic metabolisms), and iv) centers of origin (e.g., temperate vs. tropical environments). Additionally, the database includes genotypes carrying single and/or double mutations modifying their fatty acid composition (e.g., high oleic, high oleic/low linolenic mutations). Data were gathered from plants grown under diverse environmental conditions (e.g., in field settings across different locations and sowing dates, in greenhouses, or growth chambers). Statistical analyses confirmed that the database was balanced. Although sunflower was the most represented species, the established models were not spurious due to an unequal distribution of species in the database.

The meta-analysis conducted in this study investigated the response of fatty acids to temperature, despite variations of more than tenfold in the percentages of some fatty acids among the studied genotypes and species (e.g., 7-93% for oleic acid, 0.7-92% for linoleic acid). Meta-analytic approaches have previously been employed successfully to study the variability and environmental responses of other traits (Poorter et al., 2010; Challinor et al., 2014; Van and McHale, 2017; de Borja Reis et al., 2021; Secchi et al., 2023; Ngidi et al., 2024). This work extends its application to the response of fatty acids to temperature across a wide range of genotypes from different species, cultivated under varying temperature conditions during the oil synthesis stage, essential to produce oils with better quality for human consumption. Moreover, the methodology used in this work to establish common responses of seed oil fatty acids to temperature could be applied to analyze other traits. For instance, it could be applied to study the membrane fatty acids changes in leaves with temperature variations (e.g. Falcone et al., 2004), and, consequently, determine the acclimation temperature for a set of species and genotypes.

Saturated fatty acids consistently exhibited a lower response to temperature compared to unsaturated fatty acids across all established models. This work generalizes the differences in responses between genotypes of multiple species, although the analyzed works have carried out empirical research on a reduced number of genotypes in a few species (e.g., Baux et al., 2008, 2013; Agosti, 2011; Zuil et al., 2012; Schulte et al., 2013; Regitano Neto et al., 2016; Angeloni et al., 2017). The differential responsiveness of saturated and unsaturated fatty acids to temperature could be attributed to variations in the thermal sensitivity of the enzymatic complexes involved in their synthesis. FAS II (responsible for the elongation of palmitic to stearic acids) and SAD (responsible for the desaturation of stearic to oleic acids) exhibit slight temperature lability (Martínez-Force et al., 1998). FAD2 (responsible for the desaturation of oleic to linoleic acids) and FAD3 (responsible for the desaturation of linoleic to linolenic acids) are significantly sensitive to temperature variations (Martinez-Rivas et al., 2001; Cahoon and Schmid, 2008). This was observed by other authors in the species analyzed here [e.g., soybean (Zhao et al., 2019), maize (Narayanan et al., 2020), olive (D’Angeli and Altamura, 2016), flax (Pushkova et al., 2024)] and in other species not considered in this work due to their low oil content [e.g., banana (Cheng et al., 2022), cucumber (Dong et al., 2016)].

Different unsaturated fatty acids demonstrated varying degrees of sensitivity to temperature. The response of oleic acid was more pronounced compared to that of linoleic and linolenic acids. This discrepancy may be attributed to the higher thermal sensitivity of the FAD2 complex, which decreases its activity with increasing temperatures (Garcés et al., 1992; Martínez-Rivas et al., 2000, 2001). Conversely, the FAD3 complex, responsible for the desaturation of linoleic to linolenic acid, exhibits considerably lower sensitivity to temperature (Vuorinen et al., 2014). Furthermore, the response of oleic acid to temperature varied significantly among species, indicating genetic variability in the sensitivity of oleic acid to temperature, even within wild-type genotypes. Overall, the findings of this study support the idea that not only have genes involved in fatty acid synthesis pathways been conserved through evolution and genetic improvement (Celik Altunoglu et al., 2018), but also that the response of different fatty acids to temperature is preserved.

Considering the current context of climate change, where increases in minimum temperature are observed, a decrease in the degree of oil unsaturation in seeds of diverse species has been evidenced. While this may be considered positive from a consumption standpoint, it could have a negative impact on the seed when planted. In this sense, the temperature of the zone where the seed is produced determines its fatty acid composition, its saturation index, and therefore the rate at which it will germinate, depending on whether it is sown in a colder or warmer region (Izquierdo et al., 2017).

Oleic acid in HO genotypes across different species did not exhibit a response to temperature, as evidenced by comparisons between HO and WT models. Previous studies have reported that the HO trait decreases the temperature responsiveness of oleic acid (e.g., Baux et al., 2008; Izquierdo and Aguirrezábal, 2008; Alberio et al., 2018). However, conflicting results have been observed in some genotypes of soybean and sunflower (e.g., Zuil et al., 2012; Angeloni et al., 2017). The results presented here generalize that a positive temperature response of oleic acid is attributable only to WT genotypes, whereas it is null in those carrying the HO trait. Therefore, the findings also indicate that breeding efforts have successfully improved oil quality. Including the HO trait in genotypes from various species has increased the levels of oleic acid (e.g., Soldatov, 1976; Leon et al., 2013), while also decreasing its temperature responsiveness, nearly eliminating it. Thus, HO genotypes can maintain stable oil quality almost independently of the growth environment.

Other traits apart from HO did not alter the response of fatty acids synthesized upstream or downstream of the mutation in the fatty acid synthesis pathway. Both in genotypes carrying single (HS or HL) or double mutations (HSHL or HOLL), the responses of all fatty acids to temperature fell within the predicted ranges of those responses included in the appropriate models (HO or WT). The few responses outside these predicted ranges (6% of cases) were detected when the phenotypic response of a fatty acid coincided with the coding trait. The non-effect of these traits different than HO on the temperature responses of other fatty acids has not been previously reported. These results extend the validity of the HO or WT models to genotypes of sunflower and rape carrying mutations other than HO, as well as when combined with the HO trait. Thus, they demonstrate that the models established in this study could be utilized as tools to assess the impact of including mutations in the fatty acid synthesis pathway (e.g., for predicting the temperature response of fatty acids for “in silico” genotypes carrying single or double mutations).

The establishment of distinct models from subsequent dissections of the dataset facilitated the identification of previously unknown behaviors in the responses of fatty acids to temperature. For instance, in HO genotypes, the response of linoleic acid to temperature (synthesized from oleic acid) was enhanced. This finding was corroborated by the responses of linoleic acid in SF-HO and RSM-HO models. However, the HO trait did not influence the responses of fatty acids synthesized downstream (linoleic and linolenic acids) or upstream (SF and RSM) of oleic acid. Interestingly, the effect of the HO mutation on the temperature response of linoleic acid observed in HO sunflower genotypes was not observed when the HO trait was combined with other mutations in the fatty acid pathway. Thus, it is suggested that the increased temperature response of linoleic acid in SF-HO could be nullified when the HO trait is combined with other mutations. Empirical research to test this model-based hypothesis could be valuable for verifying this suggestion.

Plants grown under field conditions and those under controlled conditions exhibited similar temperature responses for all fatty acids across genotypes of different species, except for the response of oleic acid in WT genotypes of sunflower. This novel finding is significant, as it has been debated whether results obtained under controlled conditions can be extrapolated to predict plant responses in the field (i.e., Poorter et al., 2012, 2016). However, the results of this study support those investigations into the trait “response of oil fatty acids to temperature” can be conducted indistinctly under controlled conditions, in the field, or by merging data obtained under both conditions. Overall, this new knowledge could aid in designing more cost-effective and less time-consuming experiments.

The General Model can be used to determine the response of different fatty acids in all species and genotypes considered in this study. Since all genotypes of the species tested for validation were WT, the response of certain fatty acids better fit with the WT model or RSM model (WT) than with the General or RSM model (which includes HO genotypes). In olive, different trends were observed in the response of oleic acid to temperature when considering the mesocarp or the seed in the tested models. However, the data for both olive seeds and mesocarps fell within the prediction intervals of the relationships included in the four models. Moreover, these models could help identify favorable environments for producing seeds that germinate better under low-temperature conditions. Indeed, the germination of various species, including canola, sunflower, wheat, soybean, safflower, flax, cotton, quinoa, rice, among others, is related to the iodine index (which measures oil unsaturation), with linoleic acid particularly important for sunflower (Izquierdo et al., 2017). These favorable environments could be identified for current and future climate scenarios by combining the models presented in this study with the methods applied by Angeloni et al. (2017).

The meta-analytic method employed in this study revealed some limitations when the response of fatty acids was low [e.g., nearly HO isolines of the same species (Alberio et al., 2018)] or when the range of temperature variation during the experiment was narrow [e.g., <2°C (Rondanini et al., 2014; Zemour et al., 2021; Abou Chehade et al., 2022)]. These limitations arose because the temperature range explored here was 17°C (8.7 - 27.0°C), and the intervals used to establish the models were fixed at 2°C (tolerance error = 1.5°C). Thus, the validity of the established models could not be tested for some genotypes of olive, safflower, and camellia, as their data covered a temperature range of <2°C. Reducing the temperature intervals from 2°C to 1°C could increase the errors in the response slopes of different fatty acids to temperature. Moreover, decreasing the total range of explored temperatures to accommodate the excluded genotypes would reduce the number of species considered in the established models.

Sunflower has traditionally been considered as a “model” oilseed species for studying the environmental effects on fatty acid composition (Aguirrezábal et al., 2015). However, sunflower WT genotypes exhibited i) a more pronounced response of fatty acids to temperature than genotypes of other studied species and ii) a different temperature response of oleic acid between plants grown under controlled conditions and those in the field. Additionally, an effect of the HO trait on the response of linoleic acid to temperature was detected exclusively in sunflower. Therefore, it would be suggested that species other than sunflower should be considered as models for studying the response of fatty acids to environmental conditions. Rapeseed would be potentially a candidate because i) its fatty acid response to temperature was similar to that of genotypes of other species studied here, ii) its oil contains measurable linolenic acid (unlike sunflower), iii) it is globally cultivated, and iv) its genetics are closer to Arabidopsis thaliana (the model species in plant science) than sunflower (Delourme et al., 2006). However, this suggestion would need to be confirmed with further investigation of the response of rapeseed oil fatty acids to minimum temperatures above 16°C, whose process could be accelerated by using the methodology and tools developed here. A current challenge in plant science is linking genotype to phenotype (Barba-Espin and Acosta-Motos, 2022). However, phenotyping is laborious and time-consuming (Hall and Richards, 2013; Tardieu and Parent, 2017). By employing a meta-phenomic approach (e.g., Poorter et al., 2022), this study provides methods, novel insights, and tools to facilitate more efficient, rapid, and cost-effective phenotyping of fatty acid responses to temperature (Fiorani and Schurr, 2013; Tardieu and Parent, 2017; Peirone et al., 2018; Pieruschka and Schurr, 2019). The results presented here could aid in assessing a priori the potential response of fatty acids to temperature in species and genotypes not previously studied, using a small number of points that could be obtained from experiments carried out under controlled conditions, as results presented previously suggested. This could be particularly significant for “orphan” crops, which have niche markets in local economies but limited research. These crops have been underexplored but may present new opportunities in the context of climate change (Mabhaudhi et al., 2019).

We presented the effectiveness of several phenotypic models in summarizing the temperature responses of seed oil fatty acids across a range of crop species using meta-phenomics. The established models, particularly the General Model, that includes data from seed oil fatty acids of sunflower, rapeseed, soybean and maize, exhibited robustness in predicting the phenotypic responses of palmitic, stearic, oleic, linoleic, and linolenic acids in oils derived from a wide array of globally cultivated species and orphan crops. These models possess broad applicability, enabling extrapolation to predict fatty acid responses to temperature in genetically and morphologically distinct species, as well as in genotypes harboring mutations within the fatty acid biosynthetic pathway, such as sunflower or rapeseed with minimal effort devoted to experimental validation.

The standardized models of fatty acid response to temperature delineated in this research are poised to inform future endeavors aimed at improving oil quality across different species and genotypes. Additionally, they offer a framework for designing streamlined, efficient experiments that require less time and resources.

This work is the first attempt to the establishment of a general response model of the seed fatty acid to temperature. Additional research accounting for the response of fatty acid to temperature in species less or not considered in this work will be needed to increase the robustness of the analysis conducted here, allowing researchers and breeders alike to help farmers predict the outcomes they see when growing different oilseed crops.