Genetic Map-Based Analysis of Paleopolploidy in Homosporous Ferns

世界上的植物包括同孢子植物和异孢子植物，前者以蕨类植物为代表，后者以种子植物为代表。同源孢子物种具有较高的染色体数量，这表明它们是染色体数量翻倍(多倍体)之后基因/基因组沉默的重复循环的产物。该项目将解决古代多倍体的问题，方法是为里氏蕨属植物的39条染色体生成高分辨率的遗传图谱，这种蕨类植物被用作同源孢子植物研究的模式生物。来自500个完全近交杂交植物(DHL)的DNA将用大约1000个分子标记进行分析。对重复标记的染色体位置的分析将使人们有可能确定Ceratopteris物种是否是古老的多倍体。同孢子植物现在已知与种子植物有一个直接的共同祖先，种子植物是包括所有农业食用植物的一个类群。该项目的遗传图谱将提供有关同种孢子植物基因组结构的基本信息，这些信息反过来将提供与进化过程有关的基本比较数据，这些进化过程产生了今天所有植物的基因组组织。除了遗传图谱外，还将克隆500株完全分型的DHL植物，并免费提供给生物学家用于未来的遗传研究。

The world's plants consist of homosporous plants, best represented by ferns, and heterosporous plants, best represented by seed plants. Homosporous species have high chromosome numbers, suggesting that they are products of repeated cycles of doubling of chromosome numbers (polyploidy) followed by gene/genome silencing. This project will address the question of ancient polyploidy by generating high resolution genetic maps of the 39 chromosomes of Ceratopteris richardii, the fern species used as a model organism for studies of homosporous plants. DNAs from 500 completely inbred hybrid plants (DHLs) will be analyzed with approximately 1000 molecular markers. Analyses of the chromosomal locations of duplicate markers will make it possible to determine whether the Ceratopteris species is an ancient polyploid.Homosporous plants are now known to share an immediate common ancestor with seed plants, a group that includes all agricultural food plants. This project's genetic maps will provide fundamental information about genomic structure of homosporous plants, which in turn will provide basic comparative data bearing on evolutionary processes that produced the genomic organization of all of today's plants. In addition to the genetic maps, the 500 fully genotyped DHL plants will be cloned and made freely available to biologists for future genetic studies.