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Recent origins of sperm genes in Drosophila.

ABSTRACT: Newly created genes often acquire testis-specific or enhanced expression but neither the mechanisms responsible for this specificity nor the functional consequences of these evolutionary processes are well understood. Genomic analyses of the Drosophila melanogaster sperm proteome has identified 2 recently evolved gene families on the melanogaster lineage and 4 genes created by retrotransposition during the evolution of the melanogaster group that encode novel sperm components. The expanded Mst35B (protamine) and tektin gene families are the result of tandem duplication events with all family members displaying testis-specific expression. The Mst35B family encodes rapidly evolving protamines that display a robust signature of positive selection within the DNA-binding high-mobility group box consistent with functional diversification in genome repackaging during sperm nuclear remodeling. The Mst35B paralogs also reside in a significant regional cluster of testis-overexpressed genes. Tektins, known components of the axoneme, are encoded by 3 nearly identical X-linked genes, a finding consistent with very recent gene family expansion. In addition to localized duplication events, the evolution of the sperm proteome has also been driven by recent retrotransposition events resulting in Cdlc2, CG13340, Vha36, and CG4706. Cdlc2, CG13340, and Vha36 all display high levels of overexpression in the testis, and Cdlc2 and CG13340 reside within testis-overexpressed gene clusters. Thus, gene creation is a dynamic force in the evolution of sperm composition and possibly function, which further suggests that acquisition of molecular functionality in sperm may be an influential pathway in the fixation of new genes.

SUBMITTER: Dorus S

PROVIDER: S-EPMC2727386 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature

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Recent origins of sperm genes in Drosophila.

Dorus Steve S Freeman Zoë N ZN Parker Elizabeth R ER Heath Benjamin D BD Karr Timothy L TL

Molecular biology and evolution 20080724 10

Newly created genes often acquire testis-specific or enhanced expression but neither the mechanisms responsible for this specificity nor the functional consequences of these evolutionary processes are well understood. Genomic analyses of the Drosophila melanogaster sperm proteome has identified 2 recently evolved gene families on the melanogaster lineage and 4 genes created by retrotransposition during the evolution of the melanogaster group that encode novel sperm components. The expanded Mst35 ...[more]

PMID: 18653731

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Project description:The single celled eukaryote Trypanosoma cruzi, a parasite transmitted by numerous species of triatomine bug in the Americas, causes Chagas disease in humans. T. cruzi generally reproduces asexually and appears to have a clonal population structure. However, two of the six major circulating genetic lineages, TcV and TcVI, are TcII-TcIII inter-lineage hybrids that are frequently isolated from humans in regions where chronic Chagas disease is particularly severe. Nevertheless, a prevalent view is that hybridisation events in T. cruzi were evolutionarily ancient and that active recombination is of little epidemiological importance. We analysed genotypes of hybrid and non-hybrid T. cruzi strains for markers representing three distinct evolutionary rates: nuclear GPI sequences (n?=?88), mitochondrial COII-ND1 sequences (n?=?107) and 28 polymorphic microsatellite loci (n?=?35). Using Maximum Likelihood and Bayesian phylogenetic approaches we dated key evolutionary events in the T. cruzi clade including the emergence of hybrid lineages TcV and TcVI, which we estimated to have occurred within the last 60,000 years. We also found evidence for recent genetic exchange between TcIII and TcIV and between TcI and TcIV. These findings show that evolution of novel recombinants remains a potential epidemiological risk. The clearly distinguishable microsatellite genotypes of TcV and TcVI were highly heterozygous and displayed minimal intra-lineage diversity indicative of even earlier origins than sequence-based estimates. Natural hybrid genotypes resembled typical meiotic F1 progeny, however, evidence for mitochondrial introgression, absence of haploid forms and previous experimental crosses indicate that sexual reproduction in T. cruzi may involve alternatives to canonical meiosis. Overall, the data support two independent hybridisation events between TcII and TcIII and a recent, rapid spread of the hybrid progeny in domestic transmission cycles concomitant with, or as a result of, disruption of natural transmission cycles by human activities.

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Recent origins of sperm genes in Drosophila.

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Recent origins of sperm genes in Drosophila.

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