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

大多数植物，包括许多作物物种，都通过一个称为多倍化的过程经历了染色体数量的增加。多倍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如何在进化时间内对多倍化做出反应的长期研究。合成活动将侧重于表征基因组缩小现象的机制，即植物在多倍化后失去遗传物质。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，以推进关于其不同基因组结构可能起源的知识。异孢子植物，包括所有种子植物和一些无籽植物，平均染色体比同孢子植物少几倍，同孢子植物包括非维管植物以及大多数蕨类植物和石松植物。更广泛的影响将包括编写审查文件，以传播综合工作的结果。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基因组的不稳定性和不育性。尽管有50年的理论和实验，为什么同孢植物比异孢植物有更高的染色体数目的机制解释仍然难以捉摸。陆生植物的系统发育关系表明，异孢子生殖是派生条件，减数分裂过程中基因组的缩小是陆生植物这些主要类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背景下。综合活动将包括：1）综述了基因组缩小的机制，重点是二倍体与多倍体植物物种中纺锤体的形成和基因组间的易位; 2）对同孢子和异孢子植物基因组进行比较生物信息学分析，以检查在减数分裂的不同阶段表达的基因的分布，特别是与纺锤体形成相关的基因; 3）将数据和理论综合成同孢子生殖和染色体数目之间关系的全面综述;以及4）设计下一阶段的研究以检查同孢子和异孢子植物中的纺锤体形成和交换行为。这项工作的成果将提供一个综合的历史观点的方法，这一研究问题，并将推进未来的研究人员调查植物基因组evolution.This奖项的能力反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

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.