Marine Bio-Tech Fellowship: Variation in a Gamete Recognition Protein of Pacific Sand Dollars

密切相关的海洋无脊椎动物物种通常一起出现，经常同时产卵，但这些物种之间很少形成杂交。配子表面的蛋白质控制着物种特有的受精。三种证据表明，这些配子识别蛋白的变化可能与生殖隔离的进化有关：1)非可育的异种杂交通常是由于精子无法附着在异种卵子上造成的；2)亲缘关系密切、生殖隔离的物种通常表现出很少的整体遗传差异；3)选择促进了不同种类鲍鱼中精子携带的配子识别蛋白的差异。该项目将研究两个尚未解决的关键问题：1)在物种重叠的地理区域，配子识别蛋白的种间差异是否最大？ 2)物种内配子识别蛋白的变化程度如何？这两个问题将通过记录共同发生和分离的太平洋沙美元种群中精子携带的配子识别蛋白结合的核苷酸序列变化来解决。该项目将重点研究Dendraster属的成员，它们的地理分布（重叠和非重叠区域）和非常近的起源（5月1日）应该有助于区分驱动结合蛋白分化的不同进化机制。最后，结合蛋白的种间和种内变异的功能意义将通过成对受精试验进行检验。该研究项目将对种间杂交在促进配子识别蛋白分化中的潜在作用产生新的见解。* * *

9321243 Hellberg Closely related species of marine invertebrates commonly occur together and often spawn simultaneously, yet hybrids between these species rarely form. Proteins on the surface of the gametes control species-specific fertilization. Three lines of evidence suggest that changes in these gamete recognition proteins may be involved in the evolution of reproductive isolation: 1) non-fertile heterospecific crosses usually result from the failure of sperm to attach to heterospecific eggs, 2) closely related, reproductively isolated species often show little overall genetic divergence, and 3) selection promotes the divergence of sperm-borne gamete recognition proteins found in different species of abalone. This project will examine two critical questions which remain unanswered: 1) Are interspecific differences in gamete recognition proteins greatest in geographical areas of species overlap, and 2) How variable are gamete recognition proteins within species? These two questions will be addresses by documenting nucleotide sequence variation of the sperm borne gamete recognition protein bindin from both co-occurring and isolated populations of Pacific sand dollars. The project will focus on members of the genus Dendraster, whose geographical distribution (both overlapping and non- overlapping regions) and very recent origins (1 May) should facilitate discrimination between alternative evolutionary mechanisms driving bindin divergence. Finally, the functional significance of both inter-and intraspecific variation in bindin will be examined using pairwise fertilization assays. This research project should produce novel insights into the role of the potential for interspecific hybridization in promoting the divergence of gamete recognition proteins. ***