蕨类植物叶绿体RNA编辑及其适应性进化研究

RNA编辑通过在转录后水平对遗传信息重新编码来调控基因，进而影响植物的生长发育。薄囊蕨类是蕨类植物中最主要的单系群，它在被子植物兴起后，快速适应并发生了新的辐射分化。我们的前期研究发现，薄囊蕨类的RNA编辑量显著高于基部蕨类，提示高水平的RNA编辑可能在此辐射过程中发挥重要作用。基于此，本研究拟利用链特异性RNA-Seq技术，获取蕨类植物叶绿体全基因组RNA编辑信息，分析其进化式样，检验其在薄囊蕨类辐射分化中的作用。研究内容包括：1）选取从基部蕨类到真水龙骨类薄囊蕨的代表植物，明确其叶绿体RNA编辑的类型、频率和分布模式；2）阐明RNA编辑与薄囊蕨类多样性的相关性；3）开展RNA编辑的适应性进化分析，鉴定与薄囊蕨类辐射扩张相关的适应性编辑位点。本项目首次将RNA编辑与特定植物类群的辐射分化联系起来，以一个全新的角度探索薄囊蕨类适应性辐射的形成机制，将丰富和深化对RNA编辑进化意义的认识。

RNA editing could recode the genetic information at post-transcriptional level to modify gene function and regulation. Our analyses have suggested that leptosporangiates have extremely higher levels of chloroplast RNA editing than that in basal fern lineages. Leptosporangiates are the largest monophyletic group within ferns. Recent studies have shown that the major diversity of living leptosporangiate ferns is mostly the result of a new radiation beginning in the Cretaceous, following the rise of angiosperms. Hence, it appears that leptosporangiates have successfully adapted and somehow been able to capitalize upon the angiosperm-dominated terrestrial ecosystems. The high levels of chloroplast RNA editing in leptosporangiates might play important roles in their rapid adaption and new radiation. In this study, we plan to carry out genome-wide identifications of chloroplast RNA editing sites in ferns by strand-specific RNA sequencing (RNA-Seq) tool, and then perform adaptive evolution analyses of RNA editing to verify its essential role in leptosporangiates’ adaption and diversity. The RNA editomes will be obtained from all the representatives from basal ferns to eupolypods, the major lineage resulting from the new radiation. Three specific issues will be investigated: 1) What are the differences of the type, frequency and genomic distribution of RNA editing between leptosporangiates and basal ferns? 2) Does the abundance of RNA editing correlate with the diversity of leptosporangiates? Was their diversification in fact linked to the large number of RNA editing sites? 3) Is there any advantageous or adaptive RNA editing in leptosporangiates related to the radiation? What are they? And what are their potential biological functions? This study firstly connects the RNA editing to a specific radiation event and provides new insights into the explanation of the radiation. The results will deepen our understanding of the evolution and importance of RNA editing.