Guo Yanjun, Zhao Xiao, Li Yang, Li Zhen, Xiao Qianlin, Wang Yanmei, Zhang Xuefeng, Ni Yu
College of Animal Science and Technology, Southwest University, Chongqing, China.
College of Agronomy and Biotechnology, Southwest University, Chongqing, China.
Front Plant Sci. 2021 May 17;12:620245. doi: 10.3389/fpls.2021.620245. eCollection 2021.
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 (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, , , and , 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 populations in a common garden experiment. Stress-modeling experiments further validated that 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.
覆盖植物表面的表皮蜡质在帮助植物适应不断变化的环境中起着关键作用。然而，植物表皮蜡质对其生长环境的响应是否可遗传仍不清楚。我们从中国北方30个生长地点收集了（一种多年生豆科植物）种群的种子，并在一个共同园试验中研究了叶片表皮蜡质的变化。分离出四个参与主要蜡质类别（伯醇和烷烃）及蜡质前体生物合成的蜡质基因，以测试编码序列（CDS）、启动子序列和表观遗传修饰的遗传变异的贡献。通过两个胁迫模拟实验（干旱和增强紫外线B）进一步验证了表皮蜡质的可塑性响应。在共同园试验中，观察到不同种群间总蜡质覆盖量以及蜡质类别或蜡质化合物丰度存在很大差异。胁迫模拟实验进一步证实，在变化的生长条件下， 会改变叶片蜡质沉积。蜡质基因的转录水平与表皮蜡质含量呈正相关或负相关。然而，启动子甲基化分析表明，启动子区域的甲基化水平与其表达无关。尽管启动子序列和CDS都显示出许多多态性位点，但启动子未受到自然选择，不同种群间四个蜡质基因的作用元件数量和类型没有显著差异。相反，蜡质基因的CDS受到自然选择，有许多错义突变导致氨基酸、等电点和极性发生改变，这可能影响酶的功能/活性。我们得出结论，在特定环境下的长期适应会诱导蜡质生物合成基因的基因突变，导致表皮蜡质沉积的可遗传改变。
