1. P. Gonczy, B. J. Thomas and S. DiNardo (1994) roughex is a dose-dependent regulator of the second meiotic division during Drosophila spermatogenesis. Cell 77(7): 1015-25.
Abstract
During spermatogenesis, germ cells execute two meiotic divisions, then withdraw from the cell cycle and initiate postmeiotic differentiation. We show that the gene roughex (rux) is a dose-dependent regulator of meiosis II during Drosophila spermatogenesis. rux mutant germ cells execute the two meiotic divisions, but then undergo an additional M phase resembling an extra meiosis II. Conversely, germ cells with excess rux function fail to undergo meiosis II. rux does not appear to act directly at meiosis II. Rather, rux appears to act through cyclin A during premeiotic G2 to regulate meiosis II. We propose that cyclin A-cdc2 kinase at the G2 to M transition of meiosis I activates a target necessary for meiosis II, thereby coupling the two meiotic divisions. PMID: [8020092]
2. A. Llopart and J. M. Comeron (2008) Recurrent events of positive selection in independent Drosophila lineages at the spermatogenesis gene roughex. Genetics 179(2): 1009-20.
Abstract
Our understanding of the role of positive selection in the evolution of genes with male-biased expression can be hindered by two observations. First, male-biased genes tend to be overrepresented among lineage-specific genes. Second, novel genes are prone to experience bursts of adaptive evolution shortly after their formation. A thorough study of the forces acting on male-biased genes therefore would benefit from phylogenywide analyses that could distinguish evolutionary trends associated with gene formation and later events, while at the same time tackling the interesting question of whether adaptive evolution is indeed idiosyncratic. Here we investigate the roughex (rux) gene, a dose-dependent regulator of Drosophila spermatogenesis with a C-terminal domain responsible for nuclear localization that shows a distinct amino acid sequence in the melanogaster subgroup. We collected polymorphism and divergence data in eight populations of six Drosophila species, for a total of 99 rux sequences, to study rates and patterns of evolution at this male-biased gene. Our results from two phylogeny-based methods (PAML and HyPhy) as well as from population genetics analyses (McDonald-Kreitman-based tests) indicate that amino acid replacements have contributed disproportionately to divergence, consistent with adaptive evolution at the Rux protein. Analyses based on extant variation show also the signature of recent selective sweeps in several of the populations surveyed. Most important, we detect the significant and consistent signature of positive selection in several independent Drosophila lineages, which evidences recurrent and concurrent events of adaptive evolution after rux formation. PMID: [18505872]
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