Much progress has been made toward understanding how meiosis works, but in only a few organisms. It is, thus, unclear which aspects and functions in meiosis are most fundamental. Nonetheless, the data from these organisms provide a solid basis for initiating an evolutionary investigation of meiosis--more specifically, meiotic genes and their encoded proteins--in a more diverse sampling of eukaryotes. The central goal of this project is to better understand the evolution and function of the meiotic process and its molecular machinery. To accomplish this, the investigator will expand his ongoing evolutionary studies of the eukaryotic recA gene family (RAD51 and DMC1) in protists by (a) isolating these genes from additional protist species representing major eukaryotic lineages, and (b) investigating possible cases of gene loss in the recA family, some of which are associated with putatively asexual species. To complement and support the proposed experimental studies, he will employ and develop appropriate computational tools to carry out a systematic and comprehensive bioinformatic analysis of additional meiotic genes and proteins. This bioinformatic "data-mining" should result in the identification and initial characterization of key genes encoding meiotic proteins from all available eukaryotic (especially protist) species. In addition to providing information on the function and evolution of meiotic proteins, a major priority of this work is to establish when meiosis evolved, be it during extant eukaryotic evolution (leaving some surviving asexual eukaryotes that lack meiosis because they never evolved it), or alternatively, prior to the diversification of eukaryotes (making contemporary asexual eukaryotes simply the descendants of sexual species which have lost this ability). Phylogenetic analyses of the meiotic genes identified from protists will be used to directly address this issue, especially those genes that have duplicated and diverged from prior non-meiotic functions. The results from this project will guide future experimental efforts to isolate and study particular meiotic genes from other relevant eukaryotic lineages.

Meiosis is the specialized cellular division cycle in which diploid cells are "reduced" to haploid cells (such as eggs and sperm), which then fuse to generate new (diploid) individuals. Meiosis is, thus, central to sexual reproduction and has been crucial in the evolution and success of eukaryotes. However, the origin and evolution of sex remains one of the major enigmas in biology. Developing a clearer evolutionary understanding of key meiotic mechanisms will not only broadly illuminate our understanding of the sexual process, but also lend insight into the evolution of proteins and the macromolecular assemblages in which they operate. Finally, these studies should clearly demonstrate the importance of combining information from model eukaryotic genetic systems with data from less well-studied organisms in a comparative evolutionary framework.

National Science Foundation (NSF)
Division of Molecular and Cellular Biosciences (MCB)
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Susan Porter Ridley
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Emory University
United States
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