关键性状的创新不仅为植物多样化奠定了基础，也为植物的进一步适应提供了可能性。因此，研究植物类群中关键创新性状的变异及其式样，有利于阐明类群的演化机制和多样化过程。近年来的一些研究表明，关键创新性状的产生和演化可能源于少数主效基因的变异。菊科头状花序是菊科植物重要的关键创新性状。前人的研究显示，CYC2类基因在菊科头状花序及其边缘小花的形态变异中具有重要作用，但很少有学者对其花序演化的分子机制进行探讨。本项目拟以菊科代表性的头状花序类型为研究对象，以菊科花序类型决定之主效基因CYC2类基因为切入点，通过对各主要谱系分支的头状花序和小花形态的比较研究，各支系CYC2类基因的克隆、测序、分子演化分析和表达模式检测，并利用甘菊的转基因体系对菊科CYC2类基因的不同拷贝进行功能验证，进而探讨菊科头状花序演化的分子机制。

Innovation of key characters during plant evolution is not only the prerequisite for diversification, but also promotes the further adaptation of plants. Therefore, studies of the variation and its pattern of key innovative characters are vital for understanding plant diversification and adaptation. Recent studies on phenotypic variations indicated the origin and evolution of key characters may only result from variation or modification of a few major effect genes. The inflorescence of Asteraceae (Compositae) is head-like, called capitulum. The formation of capitula is one of morphological innovations that helped the composite plants gain an increased fitness and thus an adaptive radiation. There are only a few studies on the mechanism of capitulum evolution although this is an important issue for the evolution of Asteraceae plants. Previous studies showed that CYC2-like genes, homologs of CYCLOIDEA genes found in Antirrhinum majus play important roles in capitulum morphogenesis of Asteraceae. In order to document the evolution mechanism of composite capitula at molecular level, the following work will be conducted: 1) comparative analysis of the pattern of capitulum variations in Asteraceae and its major lineages; 2) cloning and sequencing of the CYC2-like genes, which are decisive to composite capitulum types; 3) evolution analysis of CYC2-like genes in Asterales, especially the evolution of several CYC2-like gene members specific to Asteraceae; 4) expression analysis of CYC2-like genes in different lineages; 5) function identification of different CYC2-like genes in Chrysanthemum lavandulifolium by genetic manipulation approaches.