Barnhart Max H, McAssey Edward V, Dittmar Emily L, Burke John M
Department of Plant Biology University of Georgia Athens Georgia USA.
School of Life Sciences University of Hawai'i at Mānoa Honolulu Hawaii USA.
Plant Direct. 2022 Jul 22;6(7):e423. doi: 10.1002/pld3.423. eCollection 2022 Jul.
Seed oil composition, an important agronomic trait in cultivated sunflower, varies latitudinally across the native range of its wild progenitor. This pattern is thought to be driven by selection for a higher proportion of saturated fatty acids in southern populations compared with northern populations, likely due to the different temperatures experienced during seed germination. To investigate whether these differences in fatty acid composition between northern and southern populations correspond to transcriptional variation in the expression of genes involved in fatty acid metabolism, we sequenced RNA from developing seeds of sunflowers from Texas, USA, and Saskatchewan, Canada (the extreme ends of sunflower's latitudinal range) grown in a common garden. We found 4,741 genes to be differentially expressed between Texas and Canada, including several genes involved in lipid metabolism. Several differentially expressed lipid metabolism genes also colocalized with known oil quantitative trait loci (QTL). The genes producing stearoyl-ACP-desaturases () were of particular interest because of their known role in the conversion of fully saturated into unsaturated fatty acids. Two genes were more highly expressed in seeds from Canadian populations, consistent with the observation of increased levels of unsaturated fatty acids in seeds from that region. We also constructed a gene co-expression network to investigate regional variation in network modules. The results of this analysis revealed regional differentiation for eight of 12 modules but no clear relationship with oil biosynthesis. Overall, the differential expression of genes offers a partial explanation for the observed differences in seed oil composition between Texas and Canada, while the expression patterns of other metabolic genes suggest complex regulation of fatty acid production and usage across latitudes.
种子油成分是栽培向日葵的一个重要农艺性状，在其野生祖先的原生范围内随纬度变化。这种模式被认为是由南方种群相对于北方种群对更高比例饱和脂肪酸的选择驱动的，这可能是由于种子萌发期间经历的不同温度所致。为了研究北方和南方种群之间脂肪酸组成的这些差异是否与参与脂肪酸代谢的基因表达的转录变化相对应，我们对在美国得克萨斯州和加拿大萨斯喀彻温省（向日葵纬度范围的两端）的共同花园中种植的向日葵发育种子的RNA进行了测序。我们发现得克萨斯州和加拿大之间有4741个基因差异表达，包括几个参与脂质代谢的基因。几个差异表达的脂质代谢基因也与已知的油数量性状位点（QTL）共定位。产生硬脂酰-ACP去饱和酶的基因特别受关注，因为它们在将完全饱和脂肪酸转化为不饱和脂肪酸方面的已知作用。两个基因在加拿大种群的种子中表达更高，这与该地区种子中不饱和脂肪酸水平增加的观察结果一致。我们还构建了一个基因共表达网络来研究网络模块中的区域差异。该分析结果揭示了12个模块中的8个存在区域分化，但与油生物合成没有明显关系。总体而言，基因的差异表达为得克萨斯州和加拿大之间观察到的种子油成分差异提供了部分解释，而其他代谢基因的表达模式表明跨纬度脂肪酸生产和利用的调控复杂。
