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

在大多数动物中，拥有不同的性别被认为是理所当然的，然而大多数开花植物都是雌雄同体的。然而，大约6%的开花植物是雌雄异株的（有不同的性别），这已经在许多不同的谱系中进化了多次。许多经济上重要的植物是雌雄异株的物种，或由雌雄异株的物种发展而来（例如猕猴桃、啤酒花、大麻、葡萄、草莓、菠菜）。直到最近，不同植物获得异黄酮的分子机制一直是个谜。现在由于基因组学的进步，正在取得迅速的进展。我们以前的工作发现了存在于白杨基因组性别决定区（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。该研究计划的长期目标是提供对植物性别决定机制的新理解，并提供可应用于任何雌雄异株植物的新工具和方法。具体来说，我们将（1）完成SDR的组装（2）建立一种快速的雌雄异株物种全甲基化组扫描方法，作为性别决定的基础;（3）将这些研究扩展到包括柳树（Salix）和海浆果（Hippophae）在内的新的雌雄异株系统。(4)了解甲基化在植物二萜类基因进化中的作用;（5）了解SDR的结构如何与物种形成、种间杂交和多倍化等过程相互作用。雌雄异株的物种对加拿大很重要。在该提案中的植物中，北极星是纸浆和造纸工业的重要种植园树木，柳树是重要的生物质和生物修复作物，海浆果是草原省份快速发展的营养作物。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.