无距耧斗菜距丢失的分子机制及其适应性研究

Adaptive evolution is a central focus of evolutionary studies. The evolution from short- to long-spurred flowers in Aquilegia (Ranunculaceae) mediated by pollinator shift is a classic textbook example in evolutionary biology. However, A. ecalcarata, which is endemic to China, was suggested to have lost spurs because of pollinator-mediated selection, indicative of another evolutionary trend, i.e., from spurred to spurless. More interestingly, it is indicated that spurless Aquilegia has parallelly originated at least twice in China, the underlying mechanisms for which is yet unknown. In this project, on the basis of previous studies, we propose to investigate the process and mechanisms for the origin of A. ecalcarata by genomic comparisons of this and its closely-related species in its different areas of origin. We aim to identify the candidate genes and mutations correlated with the spurless phenotype and reveal the mechanism for the parallel loss of spurs in different areas. Finally, by taking into account of the evolutionary history of candidate genes, we intend to elucidate the molecular mechanisms and processes for the origin and adaptive evolution of A. ecalcarata. We believe that the launching of this project will not only enable the acquisition of novel results, but also facilitates the breakthroughs in the important theoretical issues, including the evolution of morphological characteristics, parallel evolution, and adaptive evolution.

适应性进化是进化生物学研究的核心和焦点。毛茛科耧斗菜属植物距由短到长的演化及其对传粉者的适应是进化生物学教科书中的经典案例。然而已有研究表明，我国特有种无距耧斗菜是由祖先种发生“距丢失”事件演化来的，而且很可能也是适应传粉者转换的结果。这表明耧斗菜属的距还存在“从有到无”的演化趋势。更有意思的是，“无距”这一性状在我国至少平行起源了两次，但背后的分子机制还不清楚。本项目拟在已有工作的基础上，选取不同起源地中遗传背景相近的无距耧斗菜和有距物种为主要研究材料，采用多种先进的研究手段，鉴定与“无距”相关联的基因组变异，明确与距丢失相关的候选基因，揭示不同起源地的无距耧斗菜距平行丢失的机制，并结合基因的进化历史，探讨无距耧斗菜起源和适应性进化的分子机制及过程。本项目的开展有望在获得创新性研究成果的同时，在关键创新性状的进化、平行进化和适应性进化的分子机制等重要理论问题上取得突破性进展。

适应性进化是进化生物学研究的核心和焦点。已有研究表明，我国特有种无距耧斗菜是由祖先种发生“距丢失”事件演化来的，而且很可能是适应传粉者转换导致的。更有意思的是，“无距”这一性状的起源很可能是多次发生的，但背后的分子机制尚不清楚。本项目在已有工作的基础上，利用全基因组重测序数据重建了无距耧斗菜及其近缘类群的系统发育关系，揭示了不同类群间的网状进化关系，发现无距耧斗菜平行起源了两次，且无距与有距类群间多次发生渐渗。我们随后运用全基因组关联分析、比较转录组、分子进化分析等方法对两次起源的机制进行了解析，鉴定到了一批参与距发育的基因，发现其中多个与“无距”相关联，且一些沉默后的确会导致距的显著缩短，很可能是引起距丢失的关键基因。另外，我们还组装了两个分支的无距耧斗菜基因组，发现了该类群相对于有距物种特有的基因组结构变化。这些研究结果不仅促进了我们对距这一关键创新性状进化机制的理解，而且为物种形成、平行进化等重要理论问题提供了资料。