Evolution of combined versus seperate sexes in flowering plants

尽管性别在有机体生物学中起着核心作用，但令人惊讶的是，人们对涉及不同性别的生殖系统是如何以及为什么产生的知之甚少。人们对性系统遗传控制的进化过程了解得更少。植物的性系统之所以引起人们的特别兴趣，不仅是因为它们在农业上的重要性，还因为它们的复杂性和为研究一般的两性分离的逐渐进化提供了独特的机会。植物类群在其性别系统中表现出可变性，具有不同的性别决定模式，是研究性别决定染色体进化的理想环境。我们选择了一个小的欧亚葫芦科分支，包括Bryonia属和Ecballium属，研究植物的分离和组合性别的进化以及性别决定染色体的进化。这个分支中的物种要么是雌雄同株，要么是雌雄异株，性系统甚至可以在种群之间变化，显然取决于栖息地。先前在实验室的工作已经澄清了这一群体的系统发育和系统地理关系。这为我们提供了一个强有力的比较框架，我们可以用它来研究不同物种染色体上性别决定区域的组织。拟议的研究将回答有关性连锁DNA区域的进化以及性染色体的起源和组成的问题。我们申请资金(1)对雄花Bryonia dioica雄性相关的AFLP标记进行上下游测序，并在分子系统发育框架中分析这些序列；(2)构建雄花Bryonia dioica BAC文库，以便通过荧光原位杂交（FISH）进行染色体绘制。本研究计划的最终目标是有助于更好地理解植物的分离和组合性别和性别决定的进化。

Despite the central role of sex in organismal biology, surprisingly little is known about how and why reproductive systems involving separate sexes have arisen. Even less is understood about the evolutionary processes that underlie the genetic control of sexual systems. The sexual systems of plants are of specific interest not just because of their obvious agricultural importance but also because of their complexity and the unique opportunity they present to study the gradual evolution of separate sexes in general. Plant groups that exhibit variability in their sexual systems and that have different modes of sex determination are the ideal context in which to study the evolution of sex determining chromosomes. We have selected a small Eurasian clade of Cucurbitaceae, comprised of the genera Bryonia and Ecballium, with which to study the evolution of separate and combined sexes in plants and the evolution of sex-determining chromosomes. Species in this clade are either monoecious or dioecious, and sexual systems can even vary between populations, apparently depending on habitat. Previous work in a lab has clarified the phylogenetic and phylogeographic relationships within this group. This provides us with a strong comparative framework that we can use to study the organization of sex determining regions on the chromosomes among the various species. The proposed study will answer questions about the evolution of sex-linked DNA regions, and the origin and composition of sex chromosomes. We request funding (1) to sequence up- and down-stream from AFLP markers linked to the male sex in Bryonia dioica and analyse those sequences in a molecular phylogenetic framework and, (2) to construct a BAC library of B. dioica in order to perform Chromosome Painting via fluorescence in-situ hybridization (FISH). The ultimate goal of this research program is to contribute to a better understanding of the evolution of separate and combined sexes and of sex-determination in plants.