新形成异源多倍体小麦减数分裂染色体稳定性快速适应性进化的遗传基础和分子机制

具有染色体数目和结构 (核型) 稳定性是所有物种的基本特征之一。多倍化是被子植物物种形成的重要方式。然而，研究表明，多倍体 (包括同源多倍体和异源多倍体) 形成早期因减数分裂异常而产生大量染色体数目和结构变异，降低其适合度、育性和竞争力。因此，多倍体个体在形成早期如何快速进化出应对突然倍增基因组的减数分裂机器，进而保证染色体数目和结构的相对稳定性是决定其能否建立有效群体进而成为新物种的必备条件之一。本项目将在我们已从新形成异源四倍体和六倍体小麦后代群体中成功筛选到具有“减数分裂染色体稳定性”表型的稳定株系基础上，通过比较基因组和转录组学分析并结合候选基因功能验证，揭示多倍体小麦形成早期如何快速进化出该重要表型的遗传基础，并探讨其可能的分子机制。本项目研究将为进一步理解多倍化如何驱动被子植物基因组进化并实现物种形成这一重要进化生物学问题提供新认知，并可能为作物多倍体育种提供新启示。

Every species has a defined karyotype with an evolved combination of chromosome number and structure, known as karyotype (Stebbins, 1971). Polyploidy has been increasingly recognized as an important route to speciation in angiosperms (Jiao et al., 2011). However, polyploid formation at the initial stage is inherently associated with numerical and structural chromosome instabilities due to malfunctioning of the otherwise highly evolved, intricate meiosis machinery to handle abruptly doubled chromosome complements. This will inevitably result in reduced fertility, organismal fitness and competitiveness. Therefore, the ability of a newly formed polyploid genome to evolve a modified meiosis machinery, in a timely manner, to accurately and efficiently deal with the doubled chromosomes is critical for the nascent polyploid individuals to become a demographically successful population, which is an essential evolutionary entity for speciation (Fowler & Levin, 2016). This issue remains poorly understood. Here, we propose to address this important evolutionary issue in newly synthesized allotetraploid and allohexaploid wheats, based on the putative mutants we already obtained which manifest the “meiotic chromosome stability” phenotype. We will execute the study by conducting extensive comparative genomic and transcriptomic analyses as well as experimental validation of the biological functions for putatively critical genes to be identified. The major goal of this proposed study is to elucidate the genetic basis underpinning the observed “meiotic chromosome stability” phenotype in both newly formed tetraploid and hexaploid wheats, and the possible molecular mechanisms thereof. Expected findings of this study will provide new insights into our further understating of the driving roles of polyploidy in plant genome evolution and speciation, and may generate useful clues to polyploid crop improvement as well.