Plant sex determination: epigenomics and genomics of evolving sex determining regions

对大多数动物来说，拥有不同的性别是理所当然的自然状态，然而大多数开花植物是雌雄同体的。然而，大约6%的开花植物是雌雄异株（有不同的性别），这在许多不同的谱系中已经进化了多次。许多经济上重要的植物是，或者是从雌雄异株物种发展而来的（如猕猴桃、啤酒花、大麻、葡萄、草莓、菠菜）。直到最近，不同植物实现雌雄异株的分子机制一直是个谜。现在，由于基因组学的进步，正在取得快速进展。我们之前的工作发现了存在于杨树基因组性别决定区（SDR）的基因，并在其中一个基因上发现了性别特异性DNA改变（甲基化）。我们现在能够在这些成果的基础上再接再厉。本研究计划的长期目标是提供对植物性别决定机制的新认识，并提供可应用于任何雌雄异株植物的新工具和方法。具体而言，我们将(1)完成SDR的组装（目前在杨树基因组的v.3中错误组装），并充分表征杨树性别特异性表达和性别特异性甲基化的模式；(2)开发一种对任何雌雄异株物种进行快速全甲基化扫描的方案，作为性别决定的门户；(3)将这些研究扩展到新的雌雄异株系统，包括柳树（Salix）和海莓（Hippophae）。(4)了解甲基化在植物雌雄异株进化中的作用；(5)了解SDR的结构如何与物种形成、种间杂交和多倍体化等过程相互作用。雌雄异株对加拿大很重要。其中，极地是纸浆和造纸业的重要人工林，柳树是重要的生物质和生物修复作物，海莓是草原省份快速发展的中性营养作物。通过与加拿大农业和农业食品（AAFC）的合作，我们的工作将允许性别鉴定和性别操纵，帮助植物育种和农艺实践。

Having separate sexes is taken for granted as a natural condition in most animals, yet the majority of flowering plants are hermaphrodite. However, around 6% of flowering plants are dioecious (having separate sexes) and this has evolved multiple times, in many different lineages. Many economically important plants are, or were developed from, dioecious species (e.g. kiwi fruit, hops, hemp, grape, strawberry, spinach). The molecular mechanisms by which different plants achieve dioecy has been mysterious until recently. Now rapid progress is being made due to advances in genomics. Our previous work discovered the genes present in the sex-determining region of the genome (SDR) of poplar (cottonwoods; Populus spp.) and discovered sex-specific DNA alterations (methylation) on one of these genes. We are now in a position to build on these results. The long-term objective of this research program is to provide a new understanding of sex-determination mechanisms in plants and to provide new tools and methods that can be applied to any plant that is dioecious. Specifically, we will (1) complete the assembly of the SDR (currently misassembled in v.3 of the Populus genome) and fully characterize the patterns of sex-specific expression and sex-specific methylation in Populus; (2) Develop a protocol for rapid whole methylome scan of any dioecious species, as a gateway into sex determination; (3) extend these studies to new dioecious systems including willows (Salix) and seaberry (Hippophae). (4) Understand the role of methylation in the evolution of dioecy in plants generally; (5) Understand how the structure of the SDR interacts with processes such as speciation, interspecific hybridization and polyploidization. Dioecious species are important to Canada. Of the plants in this proposal polars are important plantation trees for the pulp and paper industry, willows are an important biomass and bioremediation crop, and seaberry is a rapidly developing neutraceutical crop for the prairie provinces. Through collaboration with Agriculture and Agrifood Canada (AAFC) our work will allow sex identification and sex manipulation, aiding plant breeding and agronomic practice.