新性状起源的分子机制和叠加效应研究——以黑种草属植物花瓣的表型复杂化为例

Origination of new characters, or evolutionary innovation of characters, marks and drives organism evolution. Understanding how and why new characters got originated is a key to understanding the nature of evolution. Previous studies focused mainly on the characters that characterize the occurrences of large group and failed to be conclusive. Moreover, most of them overlooked the complexity of new character origination and paid no or little attention to the relationships among successively originated characters, and thus cannot explain the reason why punctuated equilibrium was formed at the morphological level. Petals of Nigella (Ranunculaceae) species, due to successive origination of several new characters, are very complex and elaborate in shape, structure and color patterning, and can be an excellent system for the study of new character origination. Here, on the basis of our earlier studies, we propose to: 1) investigate the histories and pattern of, and the relationships between, different new character origination events by conducting field, morphological and molecular systematic surveys; 2) identify the genes and developmental modules that are responsible for the formation of newly originated characters (such as pseudonectaries, short trichomes, and navy bands on lower lips, etc.) by performing extensive transcriptomic, digital gene expression (DGE), and functional analyses of representative species; 3) determine the evolutionary pattern of petal developmental trajectory and the molecular bases of the aforementioned new character origination events by using a phylostratigraphic approach on DGE data and by testing the proposed hypotheses with functional analyses; and 4) discuss the important issues related to new character origination, such as the evolutionary pattern of gene regulatory network, the additive effects between successively occurred character origination events, the molecular basis of petal elaboration, and the validity of the hourglass model. Launching of this project will not only enable the acquisition of new and exciting results, but also help make important breakthroughs in the studies related to the basis of evolutionary innovation and principles of organism evolution.

新性状的起源是生物进化的标志和基础。对新性状起源原因和机制的探究，是进化生物学的重要内容。前人的研究大多只关注与大类群起源有关的新性状，研究结果的不确定性大，而且对新性状起源问题的复杂性以及连续发生的多个新性状起源事件之间的联系关注不够。黑种草属植物的花瓣具有非常复杂的形态、结构和着色模式，是开展新性状起源分子机制以及不同新性状起源事件之间关系研究的理想体系。本项目拟在已有工作的基础上，1）通过野外考察和分子系统学研究揭示花瓣表型复杂化的过程及主要新性状起源事件发生的顺序和模式，2）通过转录组-表达谱分析和功能研究揭示控制花瓣发育及性状形成的基因和模块，3）通过对表达数据的系统发育地层学研究揭示导致各主要新性状起源的分子机制，4）通过综合分析探讨与新性状起源有关的理论问题。本项目的开展有望在获得一批创新性成果的同时，在花瓣形态和结构多样化的分子机制及生物进化的基本法则等方面取得突破性进展。

新性状的起源是生物进化的标志和基础。对新性状起源原因和机制的探究，是进化生物学的重要内容。毛茛科黑种草属（Nigella）植物的花瓣具有非常复杂的形态、结构和着色模式，是开展新性状起源分子机制以及不同新性状起源事件之间关系研究的理想体系。本项目在已有工作的基础上，采用多学科研究手段，从“进化”和“发育”两个方面，研究了复杂花瓣多样化的过程和机制以及复杂花瓣关键新性状形成和起源的分子机制。本项目取得的重要成果包括：1）重建了Nigella arvensis复合体的进化历史，发现该复合体在2.71百万年前与其他物种分化开来，复合体内部成员则伴随岛屿形成事件渐次分化；2）揭示了花瓣表型复杂化的过程和模式，认为新性状的起源和发育重塑是花瓣复杂化的主要原因，不同新性状的起源也许是在不同进化阶段适应不同环境因子的结果；3）解析了花瓣发育调控网络及相关功能模块，发现花瓣形态和结构的差异是在发育过程中逐步建立的，某些程序在调用时间上的差异以及关键基因在表达时、空和量上的改变，很可能与花瓣形态和结构的变化，甚至是新性状起源的密切相关；4）阐明了重要新性状起源的分子机制，发现背腹性基因的表达重排、YAB5的异位表达、TT8的表达改变以及色素相关基因的差异表达可能是二唇形结构、假蜜腺、短表皮毛和眉毛状条带形成和起源的关键。总之，依托本项目，我们获得了多个物种（亚种）的植物材料，积累了大量形态学、解剖学、“组”学和相关基因的功能数据，发展了先进的形态学和功能研究平台以及生物信息学分析平台，已将黑种草属植物开发为研究新性状起源的模式体系。本项目在Nature Plants、Nature Communications和New Phytologist等期刊上发表文章3篇；在Science上合作发表论文1篇。这些成果的取得不仅有助于深入理解花瓣表型复杂化的过程、原因和机制，而且为研究新性状起源和叠加效应提供了新思路。

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