Male Sex Interspecies Divergence and Down Regulation of Expression of Spermatogenesis Genes in Drosophila Sterile Hybrids |
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Authors: | Vignesh Sundararajan Alberto Civetta |
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Institution: | (1) Department of Biology, University of Winnipeg, 515 Portage Ave., Winnipeg, MB, R3B 2E9, Canada; |
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Abstract: | Male sex genes have shown a pattern of rapid interspecies divergence at both the coding and gene expression level. A common
outcome from crosses between closely-related species is hybrid male sterility. Phenotypic and genetic studies in Drosophila sterile hybrid males have shown that spermatogenesis arrest is postmeiotic with few exceptions, and that most misregulated
genes are involved in late stages of spermatogenesis. Comparative studies of gene regulation in sterile hybrids and parental
species have mainly used microarrays providing a whole genome representation of regulatory problems in sterile hybrids. Real-time
PCR studies can reject or reveal differences not observed in microarray assays. Moreover, differences in gene expression between
samples can be dependant on the source of RNA (e.g., whole body vs. tissue). Here we survey expression in D. simulans, D. mauritiana and both intra and interspecies hybrids using a real-time PCR approach for eight genes expressed at the four main stages
of sperm development. We find that all genes show a trend toward under expression in the testes of sterile hybrids relative
to parental species with only the two proliferation genes (bam and bgcn) and the two meiotic class genes (can and sa) showing significant down regulation. The observed pattern of down regulation for the genes tested can not fully explain
hybrid male sterility. We discuss the down regulation of spermatogenesis genes in hybrids between closely-related species
within the contest of rapid divergence experienced by the male genome, hybrid sterility and possible allometric changes due
to subtle testes-specific developmental abnormalities. |
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