Molecular basis of reproductive isolation in blue mussels (Myrtilus, Bivalvia): Identification and characterization of gamete-specific factors

无底海洋无脊椎动物自由产卵是研究生殖隔离分子机制的一个很好的模型系统。这是因为在这些生物中，物种识别的过程（合子前分离机制）几乎完全局限于配子相互作用的过程。一个非常适合研究无根海洋无脊椎动物配子相互作用的例子是Mytilus edulis物种复合体（Mytilus edulis， M. trossulus和M. galloprovincialis），因为世界各地都存在异域种群，它们在种间接触区杂交。以往的研究主要集中在编码顶体蛋白M7溶酶的单个基因的分子进化上。这里概述的项目旨在寻找在精子和卵子的所有细胞区室中参与配子相互作用的广泛候选因素。选择性抗体生产将用于识别新的因子，抗体将用于这些分子的初始功能表征。重点将放在寻找相关的蛋白质和相应的基因上。选定的蛋白质将比较分析，以调查其分子进化模式，通过观察异域贻贝种群。此外，本研究中发现的因素将根据其在生殖隔离中的作用进行功能表征，这两种方法是：i)人工授精试验和ii)波罗的海毛毛鼠-托苏鼠接触区物种特异性等位基因频率分析。该项目的最终目标是了解海洋无脊椎动物在外部配子相互作用/受精条件下的生殖隔离功能和进化。

Free spawning sessile marine invertebrates are an excellent model system to study molecular mechanisms underlying reproductive isolation. This is because the process of species recognition (pre-zygotic isolation mechanism) is almost entirely restricted to the process of gamete interaction in these organisms. A well suited example to study gamete interaction in sessile marine invertebrates is the Mytilus edulis species complex (M. edulis, M. trossulus, and M. galloprovincialis) because allopatric populations exist worldwide which hybridise in zones of interspecies contact. Previous studies mainly focussed on the molecular evolution of a single gene encoding the acrosomal protein M7 lysin. The project outlined here aims at searching for a broad range of candidate factors involved in gamete interaction occurring in all cellular compartments of sperm and eggs. Selective antibody production will be used to identify new factors and the antibodies will be used for initial functional characterization of these molecules. A strong focus will lie on finding relevant proteins and their corresponding genes. Selected proteins will be comparatively analysed to investigate patterns of their molecular evolution by looking at allopatric Mytilus populations. Furthermore, factors found in this study will be functionally characterized in respect to their role in reproductive isolation based on two approaches: i) insemination assays, and ii) analysis of species specific allele frequencies in the Baltic M. edulis – M. trossulus contact zone. The ultimate goal of the project is an understanding of function and evolution of reproductive isolation under the conditions of external gamete interaction/fertilization in a marine invertebrate.