Conservation and Divergence of Floral Regulatory Gene Function in Angiosperm Evolution

本项目的长期目标是了解保守的调控基因产物及其表达模式之间的差异如何促进不同被子植物中不同花形态的进化。对拟南芥（Arabidopsis）和Antirrhinum等模式系统的研究，已经形成了一个模型来解释花器官识别基因之间的相互作用，以确定双梗花的基本轮系、萼片、花瓣、雄蕊和心皮。这个模型在多大程度上可以解释形态截然不同的花朵的发育，比如在草类物种中发现的花朵，这在很大程度上是未知的。此外，草的非生殖器官和菊科花之间的进化关系一直是争论的主题。施密特博士的实验室将通过阐明控制玉米花器官规格和发育的潜在机制来解决这些问题。MADS-box基因已被证明是双朵花器官身份的主要决定因素，并且是器官规格的ABC模型的主要贡献者。通过基因克隆、系统发育分析、基因表达模式比较和突变分析的结合，Schmidt博士的团队已经能够在特定的玉米MADS-box基因和来自拟南芥和Antirrhinum的相应器官身份基因之间建立同源关系。他们现在可以更详细地探索这些玉米MADS-box基因在确定草花发育中的作用，草花的花形态与双子叶植物的花不同。这些研究将使他们的团队能够直接测试花器官身份的ABC模型适用于玉米高度衍生的草花的程度。此外，这些研究将提供遗传和分子数据，有助于解决双穗花被器官与草小穗非生殖器官的同源性问题。这些研究将为理解调控基因的差异如何促进不同形态的进化提供重要的见解。

This project addresses the long term goal of understanding how differences among conserved regulatory gene products and their patterns of expression have contributed to the evolution of distinct floral morphologies among divergent angiosperms. Studies in model systems like Arabidopsis and Antirrhinum have led to the formulation of a model to explain the interaction among floral organ identity genes in specifying the basic whorls of the dicot flower, the sepals, petals, stamens and carpels. To what degree this model can account for the development of flowers with strikingly different morphologies, such as those found in grass species, is largely unknown. Furthermore, the evolutionary relationship between the nonreproductive organs of grass and dicot flowers has long been the subject of debate. Dr. Schmidt's lab will approach these questions by elucidating the underlying mechanisms controlling floral organ specification and development in Zea mays.MADS-box genes have been shown to be primary determinants of organ identity in dicot flowers, and are major contributors to the ABC model of organ specification. By a combination of gene cloning, phylogenetic analysis, comparison of patterns of gene expression, and mutational analysis, Dr. Schmidt's group has been able to establish orthologous relationships between specific maize MADS-box genes and corresponding organ identity genes from Arabidopsis and Antirrhinum. They are now in a position to explore in some detail the role of these maize MADS-box genes in specifying the development of the grass flower, a flower in which the floral morphology is distinct from that of dicotyledonous plants. These studies will enable their group to directly test the degree to which the ABC model of floral organ identity applies to the highly derived grass flowers of maize. In addition, these studies will provide genetic and molecular data that will help resolve the question concerning homologies between the perianth organs of dicots and the nonreproductive organs of the grass spikelet. These studies will provide important insight into understanding how divergence in regulatory genes can contribute to the evolution of distinct morphologies.