Evolution of combined versus seperate sexes in flowering plants

尽管性在生物生物学中扮演着核心角色，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出现的知之甚少。对性系统基因控制的进化过程更是知之甚少。植物的有性系统之所以特别令人感兴趣，不仅是因为它们具有明显的农业重要性，还因为它们的复杂性，以及它们为研究总体上不同性别的逐渐进化提供了独特的机会。具有不同性别决定模式的植物种群在其有性系统中表现出可变性，是研究性别决定染色体进化的理想环境。我们选择了欧亚葫芦科的一个小分支，由苔藓属和杂色葫芦属组成，用它来研究植物中分离和组合的性别的进化以及决定性别的染色体的进化。这一分支中的物种要么是雌雄同株的，要么是雌雄异株的，性系统甚至可以在不同的种群之间变化，显然取决于栖息地。之前的一项实验室工作已经澄清了这一组中的系统发育和系统地理关系。这为我们提供了一个强大的比较框架，我们可以用它来研究不同物种之间染色体上性别决定区域的组织。这项拟议的研究将回答有关与性相关的DNA区域的进化以及性染色体的起源和组成的问题。我们请求资金(1)从与雄性相关的AFLP标记的上游和下游测序，并在分子系统发育框架中分析这些序列，以及(2)构建B.dioica的BAC文库，以便通过荧光原位杂交(FISH)进行染色体绘制。这项研究计划的最终目的是为了更好地理解植物中分离和结合的性别以及性别决定的进化。

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.