Data_Sheet_3_Environment-Driven Adaptations of Leaf Cuticular Waxes Are Inheritable for Medicago ruthenica.CSV

Cuticular waxes covering the plant surface play pivotal roles in helping plants adapt to changing environments. However, it is still not clear whether the responses of plant cuticular waxes to their growing environments are inheritable. We collected seeds of Medicago ruthenica (a perennial legume) populations from 30 growing sites in northern China and examined the variations of leaf cuticular waxes in a common garden experiment. Four wax genes, MrFAR3-1, MrFAR3-2, MrCER1, and MrKCS1, involved in biosynthesis of predominant wax classes (primary alcohol and alkane) and wax precursors, were isolated to test the contributions of genetic variations of the coding sequences (CDS) and the promoter sequences and epigenetic modifications. The plasticity responses of the cuticular waxes were further validated by two stress-modeling experiments (drought and enhancing ultraviolet B). Great variations in total wax coverage and abundance of wax classes or wax compounds were observed among M. ruthenica populations in a common garden experiment. Stress-modeling experiments further validated that M. ruthenica would alter leaf wax depositions under changed growing conditions. The transcriptional levels of the wax genes were positively or negatively correlated with amounts of cuticular waxes. However, the analysis of promoter methylation showed that the methylation level of the promoter region was not associated with their expressions. Although both promoter sequences and CDS showed a number of polymorphic sites, the promoters were not naturally selected and insignificant difference could be observed in the numbers and types of acting elements of the four wax genes among populations. In contrast, the CDS of the wax genes were naturally selected, with a number of missense mutations resulting in alterations of the amino acid as well as their isoelectric points and polarities, which could impact on enzyme function/activity. We conclude that long-term adaptation under certain environments would induce genetic mutation of wax biosynthesis genes, resulting in inheritable alterations of cuticular wax depositions.

覆盖于植物体表的表皮蜡质，在帮助植物适应多变环境的过程中发挥关键作用。但目前尚不清楚植物表皮蜡质对生长环境的响应是否可遗传。我们从中国北方30个生境采集了扁蓿豆（Medicago ruthenica，多年生豆科植物）种群的种子，并通过同质园实验探究了其叶片表皮蜡质的变异情况。我们分离得到4种蜡质合成相关基因：MrFAR3-1、MrFAR3-2、MrCER1及MrKCS1，这些基因参与主要蜡质组分（初级醇与烷烃）及蜡质前体的生物合成，以此来探究编码序列（Coding Sequence，CDS）、启动子序列的遗传变异以及表观遗传修饰所产生的影响。我们进一步通过两种胁迫模拟实验（干旱胁迫与紫外B增强胁迫）验证了表皮蜡质的可塑性响应。同质园实验结果显示，不同扁蓿豆种群的总蜡质覆盖度以及蜡质组分或化合物的丰度均存在显著差异。胁迫模拟实验进一步证实，扁蓿豆可在生长环境改变时调整叶片蜡质沉积量。蜡质合成基因的转录水平与表皮蜡质含量呈显著正相关或负相关。但启动子甲基化分析结果显示，启动子区域的甲基化水平与这些基因的表达并无关联。尽管启动子序列与编码序列均存在多处多态性位点，但启动子并未经历自然选择，且不同种群间4个蜡质基因的顺式作用元件的数量与类型均无显著差异。与之相反，蜡质基因的编码序列经历了自然选择，存在多处错义突变，这些突变会改变氨基酸序列及其等电点与极性，进而可能影响酶的功能或活性。综上，特定环境下的长期适应会诱导蜡质合成基因发生遗传突变，进而导致表皮蜡质沉积的可遗传改变。