近日，华中农业大学园艺植物生物学教育部重点实验室刘继红教授团队研究成果以“CHH methylation of genes associated with fatty acid and JA biosynthesis contributes to cold tolerance in autotetraploids of Poncirus trifoliata”为题的研究论文在Journal of Integrative Plant Biology发表，该研究从DNA甲基化和转录水平上揭示了柑橘多倍体抗寒的分子调控机制。
柑橘是世界第一大水果，也是我国南方最重要的水果，但柑橘产业受到多种非生物逆境的制约。因此，研究柑橘资源非生物逆境应答的分子调控机制具有重要理论意义和潜在应用价值。枳（Poncirus trifoliata （L.） Raf. ）是柑橘上最常用的砧木，抗寒性较强，是研究低温应答的重要柑橘资源。已有研究表明，相对二倍体来说，四倍体常常具有更好的遗传适应性和抗逆性。植物全基因组加倍往往会引起表观遗传和转录水平的改变，但是这些变化如何调控多倍体抗性尚不清楚。
课题组前期通过自然群体筛选获得了一批枳同源四倍体资源，抗性评价表明，枳四倍体植株比二倍体更抗寒。对低温处理前后的二倍体和四倍体植株进行了转录组和全基因组甲基化测序，结果表明在低温处理后，二倍体和四倍体均发生了全基因组去甲基化，但四倍体甲基化水平下降更大，低温胁迫相关基因更大程度地被激活。转录组和甲基化组联合分析表明，低温条件下，多个不饱和脂肪酸和茉莉酸合成通路的关键基因（如FAD和LOX）在四倍体中都显著高表达，并且这些基因的上游或者下游区域CHH甲基化在四倍体和二倍体之间存在差异。代谢和生理测定表明，四倍体在低温胁迫下积累了更多的不饱和脂肪酸和茉莉酸。本研究首次解析了多倍体柑橘抗寒性增强的表观遗传机制，为多倍体枳的应用提供了重要理论基础，也为多倍体植物抗逆机理研究提供了重要参考。
华中农业大学园艺林学学院在读博士研究生王月为该论文第一作者，刘继红教授为通讯作者。我校毕业硕士生左兰兰和李春龙教授也参与了该研究。本研究受到国家重点研发计划项目和国家自然科学基金资助。
[英文摘要]
Polyploids have elevated stress tolerance, but the underlying mechanisms remain largely elusive. In this study, we showed that naturally occurring tetraploid plants of trifoliate orange （Poncirus trifoliata （L.） Raf.） exhibited enhanced cold tolerance relative to their diploid progenitors. Transcriptome analysis revealed that whole-genome duplication was associated with higher expression levels of a range of well-characterized cold stress-responsive genes. Global DNA methylation profiling demonstrated that the tetraploids underwent more extensive DNA demethylation in comparison with the diploids under cold stress. CHH methylation in the promoters was associated with up-regulation of related genes, whereas CG, CHG and CHH methylation in the 3'-regions was relevant to gene down-regulation. Of note, genes involved in unsaturated fatty acids （UFAs） and JA biosynthesis in the tetraploids displayed different CHH methylation in the gene flanking regions and were prominently up-regulated, consistent with greater accumulation of UFAs and JA when exposed to the cold stress. Collectively, our findings explored the difference in cold stress response between diploids and tetraploids at both transcriptional and epigenetic levels, and gained new insight into the molecular mechanisms underlying enhanced cold tolerance of the tetraploid. These results contribute to uncovering a novel regulatory role of DNA methylation in better cold tolerance of polyploids.
原文链接：https://www.jipb.net/EN/10.1111/jipb.13379
