Introgression in Helianthus (Asteraceae)

[9419206 . Rieseberg]生物物种通常被定义为种群中不与其他种群交换基因的杂交生物群体。任何阻碍两个物种之间基因交流的因素都会造成生殖隔离，从而影响单个物种的完整性和一致性。然而，物种之间的许多生理或生殖障碍并不能完全阻止基因流动，但允许少量杂交发生；这些障碍中的一些可能实际上只限制了基因流向基因组的某些区域。印第安纳大学的Loren Rieseberg博士进行这项研究的目的是通过经验来测试染色体结构差异对植物基因流动最重要的生殖障碍之一的影响。这将通过调查来自向日葵属（菊科）的两个杂交种群（加利福尼亚和俄克拉何马州）的数百株单株来完成，并利用139个特定的向日葵染色体基因组标记，这些标记是先前研究支持的结果。由于这些分子标记的染色体位置在每个亲本向日葵物种中都是已知的，并且在一些情况下位置不同，因此它们可以用来追踪特定基因或染色体片段在杂交的两个区域中跨越物种屏障的流动。这些结果将提供染色体结构差异作为生殖障碍的有效性的数据，并将表明这些障碍是否只限制了基因组结构相似区域的种间基因流动。

9419206 Rieseberg Biological species are often defined as groups of interbreeding organisms in populations that do not exchange genes with other groups. Any factor that impedes the exchange of genes between two species contributes to reproductive isolation and hence to the integrity and coherence of individual species. However, many physiological or reproductive barriers between species do not prevent gene flow completely but allow some small amount of hybridization to occur; and some of these barriers may actually limit gene flow to certain regions of the genome only. The purpose of research by Dr. Loren Rieseberg at Indiana University is to test empirically the effects of one of the most important reproductive barriers to gene flow in plants, chromosomal structural differences. This will be accomplished by surveying several hundred individual plants taken from two hybridizing populations (in California and Oklahoma) of sunflower species, genus Helianthus (Asteraceae), and by making use of 139 particular genomic markers of sunflower chromosomes already developed as a result of prior research support. Because the chromosome locations of these molecular markers are known in each of the parental sunflower species and differ in location in several instances, they can be used to trace the flow of particular genes or chromosomal segments across the species barrier in the two zones of hybridization. The results will yield data about the effectiveness of chromosomal structural differences as reproductive barriers and they will indicate whether such barriers limit interspecific gene flow to structurally similar regions of the genome only.