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

大多数植物，包括许多作物物种，都通过一种称为多倍化的过程增加了它们的染色体数量。多倍化可以产生新的适应性状，促进物种多样性，但也可能导致基因组不稳定和不育。这个项目将综合首席研究员关于植物基因组如何在进化过程中对多倍化做出反应的长期研究。合成活动将集中于描述基因组缩小现象的机制，即植物在多倍化后丢失遗传物质。然后，该项目将在同种和异种孢子的陆地植物中比较这一现象，以促进对它们不同基因组结构的可能起源的了解。异源孢子植物包括所有种子植物和一些无核植物，其平均染色体数比同源孢子植物少好几倍，同源孢子植物包括非维管植物以及大多数蕨类和番茄。更广泛的影响将包括编写审查论文，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理解多倍体作物发育过程中基因组的不稳定性和不育性。尽管经过了50年的理论和实验，但对于同源孢子植物比异源孢子植物具有更多染色体数量的机制解释仍然难以捉摸。成熟的陆生植物系统发育关系表明，异源孢子是起源的条件，减数分裂过程中基因组的缩小是这些主要陆生植物种群之间基因组结构差异的可能原因。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态的更广泛的背景下。综合活动将包括：1)综述基因组缩小的机制，重点是二倍体和多倍体植物物种的纺锤体形成和基因组间易位；2)同孢子和异孢子植物基因组的比较生物信息学分析，以研究在减数分裂不同阶段表达的基因的分布，特别是与纺锤体形成有关的基因的分布；3)综合数据和理论，全面审查同源孢子和染色体数目之间的关系；以及4)设计下一阶段的研究，以检查同源和异源孢子植物的纺锤体形成和交换行为。这项工作的成果将为这一研究问题的解决方法提供一个综合的历史视角，并将提高未来研究人员调查植物基因组进化的能力。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.