OPUS: CRS: Why do heterosporous plants have so few chromosomes?

大多数植物，包括许多作物物种，都经历了染色体数量的增加，这一过程被称为多倍体化。多倍体化可以产生新的适应性性状，促进物种多样化，但也可能导致基因组不稳定和不育。该项目将综合首席研究员关于植物基因组在进化过程中如何响应多倍体化的长期研究。合成活动将集中于描述基因组缩小现象的机制，即植物在多倍体化后失去遗传物质。然后，该项目将比较同孢子和异孢子陆地植物之间的这种现象，以推进对其不同基因组结构的可能起源的了解。异孢子植物包括所有有籽植物和一些无籽植物，它们的染色体平均比同孢子植物少几倍，同孢子植物包括无维管植物以及大多数蕨类和石松植物。更广泛的影响将包括编写评论论文，以传达综合工作的结果。这项研究的结果可能有助于农学家了解多倍体作物发育过程中的基因组不稳定性和不育。尽管有五十年的理论和实验，为什么同孢子植物比异孢子植物有更高的染色体数目的机制解释仍然难以捉摸。已建立的陆地植物系统发育关系表明，异孢子是衍生条件，减数分裂期间基因组缩小可能是导致这些主要陆地植物群体基因组结构差异的原因。首席研究员将把这个长期存在的研究问题放在所有植物基因组动力学的更广泛背景下。合成活动将包括：1)回顾基因组缩小的机制，重点是二倍体与多倍体植物物种的纺锤体形成和基因组间易位；2)比较同源和异孢子植物基因组的生物信息学分析，研究减数分裂不同阶段表达基因的分布，特别是与纺锤体形成相关的基因；3)综合资料和理论，对同孢体与染色体数目的关系进行综合评述；4)设计下一阶段的研究，以研究同质和异孢植物的纺锤体形成和交叉行为。这项工作的结果将为这一研究问题的方法提供一个综合的历史视角，并将提高未来研究人员研究植物基因组进化的能力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Most plants, and including many crop species, have undergone an increase in the number of their chromosomes through a process called polyploidization. Polyploidization can yield new adaptive traits and promote species diversification, but it can also lead to genomic instability and infertility. This project will synthesize the principal investigator's long-term research on how plant genomes respond to polyploidization over evolutionary time. Synthesis activities will focus on characterizing the mechanisms responsible for the phenomenon of genome downsizing, whereby plants lose genetic material following polyploidization. The project will then compare this phenomenon among homosporous and heterosporous land plants to advance knowledge about the possible genesis of their divergent genome architectures. Heterosporous plants, which include all seed plants and some seedless ones, have several times fewer chromosomes on average than do homosporous plants, which include non-vascular plants as well as most ferns and lycophytes. Broader impacts will include the production of review papers to communicate the results of the synthetic work. Results from this research may help agronomists understand genome instability and infertility during polyploid crop development.Despite five decades of theory and experiments, a mechanistic explanation for why homosporous plants have higher chromosome numbers than heterosporous plants has remained elusive. Well-established phylogenetic relationships of land plants show that heterospory is the derived condition and that genome downsizing during meiosis bears close investigation as a possible cause of divergent genome architectures among these major groups of land plants. The principal investigator will place this long-standing research question in a broader context of genome dynamics in all plants. Synthetic activities will include: 1) a review of mechanisms of genome downsizing, with a focus on spindle formation and intergenomic translocation in diploid versus polyploid plant species; 2) comparative bioinformatic analyses of homosporous and heterosporous plant genomes to examine distribution of genes expressed during different stages of meiosis and especially those associated with spindle formation; 3) synthesis of data and theories into a comprehensive review of the relationship between homospory and chromosome number; and 4) design of the next phase of research to examine spindle formation and crossing-over behavior in homosporous and heterosporous plants. Outcomes of the work will provide a synthetic historical perspective on approaches to this research question and will advance the ability of future researchers to investigate plant genome evolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.