毛茛科植物不同花器官排列式样的形成和演化规律研究

Variation of floral phyllotaxis plays a major role in flower evolution. It has long been assumed that one of the general trends in angiosperm evolution is the transition from spiral arrangement of flower organs to whorled one. Recent studies, however, have demonstrated that the evolutionary trend of floral phyllotaxis is not linear but rather more flexible, and the original floral phyllotaxis in angiosperms is equivocal. The family Ranunculaceae is an ideal group for studying the evolutionary relationships of different floral phyllotaxis patterns. We have found that spiral, whorled and irregular floral phyllotaxis co-exist in Ranunculaceae. Unfortunately, the formation and ancestral state of the floral phyllotaxis in Ranunculaceae are still uncertain. We are uncertain as to how the three patterns have evolved because of the large size and floral diversity of the family and only separate floral phyllotaxis studies or mature flower description for some genera. Our proposed research is a comprehensive comparative study of floral phyllotaxis in Ranunculaceae. Based on our preliminary results, we will: (1) investigate the floral formation and development of 18 species belonging to 18 different genera and 3 species of 3 genera as outgroups, using the scanning electron microscope, and identify their floral phyllotaxis patterns; (2) analyze the relationship between the variation in floral phyllotaxis patterns and the number of floral organ by mapping them on a phylogenetic tree, and (3) reconstruct the ancestral state of floral phyllotaxis patterns on the tree, and analyze the evolution of different patterns. Our work will not only answer those questions regarding the evolution of floral phyllotaxis, but also provide the basic knowledge for future research on the genetic mechanisms involved in determining phyllotaxis.

花器官排列式样的多样化是花形态多样化的重要方面。传统观点认为花器官螺旋状排列是原始的，而轮状是进化的，但近年来的研究显示二者并非直线演化关系，排列式样的祖先状态仍不清楚。毛茛科植物的花器官具有轮状、螺旋状和不规则状排列式样，是研究该问题的理想类群。由于该科花形态变异丰富，以往研究多集中在对个别属、种或成熟花中花器官排列式样的描述上，类群代表性不够，因此未能对不同花器官排列式样的形成过程、祖先状态和演化规律进行归纳总结。本项目拟在申请者以往研究工作的基础上，（1）利用扫描电子显微镜观察毛茛科不同进化支上18属18种和外类群3种植物的花器官发育过程，判断其排列式样；（2）分析花器官排列式样和花器官数目间的相关性；（3）最后，在系统发育框架下，对花器官排列式样进行祖先状态重建，揭示不同式样在该科中的演化规律。项目的实施将为不同花器官排列式样的研究提供新的视角，为其遗传机制的研究提供基本资料。

花器官排列式样的多样化是花形态多样化的重要方面，但不同排列式样的形成原因、祖先状态和演化规律仍不清楚。本项目选取毛茛科为研究对象，在以往基础上，利用扫描电子显微镜观察了不同进化支上罂粟莲花、獐耳细辛、天葵、距瓣尾囊草、Hydrastis、Glaucidium及外类群八角莲、鲜黄连、血水草等十余种代表植物的花器官发育过程，并增加了小檗科Podophyllum和罂粟科的荷包牡丹属为外类群。研究表明，在毛茛科植物花器官具有轮状、螺旋状和不规则状排列式样。依靠系统发育树分析表明，花器官轮状排列的类群花器官数目、特别是雌雄蕊数目较少；花器官螺旋状和不规则状排列的类群花器官数目较多。花器官不规则状排列主要是由于雄蕊和心皮发育过程中次生性增加导致的。祖先状态重建显示，毛茛科植物祖先节点花器官排列式样是轮状，螺旋状和不规则状是次生的，且不规则状是由螺旋状衍生的。毛茛科基部的Glaucidioideae和Hydrastidoideae两个亚科花器官排列为轮状。黄连亚科和毛茛亚科祖先节点花器官是螺旋状排列，在扁果草族、铁线莲属、类叶升麻属中花器官排列为轮状，表明由螺旋状向轮状排列式样在不同分支中逆向转化，且这种转化是平行发生的；毛茛族、银莲花族花器官为不规则螺旋排列，表明不规则螺旋是次生性状。本项目的实施为不同花器官排列式样的研究提供了新的视角，为不同花器官排列式样遗传机制的研究提供了发育形态学资料。