Analysis of Floral Homeotic Regulatory Gene Function in the Angiosperms

基于许多花同源异型基因在序列和功能上的相似性，有人提出，控制花发育的分子机制在双子叶植物中是相似的，可能在所有被子植物中也是如此。尽管如此，花表现出显著的形态多样性，人们认为特定的花器官类型可能进化了不止一次。特别是，花瓣被认为在被子植物中出现了无数次。这些独立的花瓣起源表明，不同物种中指定花瓣特性的分子机制可能不同。这一建议试图明确地检验APETALA3(AP3)和Pistillata(PI)基因在高等真叶植物中控制花瓣特性的表达和功能在其他被子植物分支中可能具有不同的作用的假说。为了开始了解AP3和PI同源基因的功能是如何随着进化时间的推移而调节的，我们提出了三组实验。首先，将在选定的被子植物物种中进行AP3和PI同源基因的表达分析，以确定它们表达的变化是否与花瓣的独立起源相关。其次，最近的工作已经确定了另一个基因TM6，它似乎是一个AP3类似基因，可能也在花瓣发育中发挥作用。矮牵牛和烟草的TM6同源基因的功能丧失表型将被产生和鉴定，以确定TMD样基因的作用。第三，最近的系统发育分析已经确定了保守的A.P3和PI羧基末端基序；将在转基因拟南芥中进行缺失和交换实验，以确定这些保守序列的作用(S)。

Based on the similarities in sequence and function of a number of floral homeotic genes, it has been proposed that the molecular mechanisms controlling floral development are similar across dicots, and perhaps across all angiosperm species. Nonetheless, flowers display remarkable morphological diversity, and it is thought that particular floral organ types may have evolved more than once. In particular, petals are thought to have arisen numerous times in the angiosperms. These independent origins of petals imply that the molecular mechanisms specifying petal identity may be different in different species. This proposal seeks to explicitly test the hypothesis that the expression and function of the APETALA3 (AP3) and PISTILLATA (PI) genes which are known to control petal identity in higher eudicot species may have different roles in other angiosperm clades. Three sets of experiments are proposed to begin to understand how the functions of AP3 and PI orthologous genes may have been modulated over evolutionary time. First, expression analyses of AP3 and PI orthologs will be carried out in selected angiosperm species to see if changes in their expression correlate with the independent origins of petals. Second, recent work has identified another gene, TM6, which appears to be an AP3 paralog and may also function in petal development. Loss-of-function phenotypes in TM6 orthologs in Petunia and Nicotiana will be generated and characterized to determine the role of TMd-like genes. Third, recent phylogenetic analyses have identified conserved A.P3 and PI carboxy-terminal motifs; deletion and swapping experiments will be carried out in transgenic Arabidopsis to determine the role(s) of these conserved sequences.