Abstract
In animals, sexual differences between males and females are usually determined by sex chromosomes. Alternatively, sex may also be determined by vertically transmitted intracellular microbial endosymbionts. The best known cytoplasmic sex manipulative endosymbiont is Wolbachia which can, for instance, feminize genetic males into phenotypic females in the terrestrial isopod Armadillidium vulgare. However, the molecular genetic basis of cytoplasmic sex determination is unknown. To identify candidate genes of feminization induced by Wolbachia strain wVulC from A. vulgare, we sequenced the genome of Wolbachia strain wCon from Cylisticus convexus, the most closely related known Wolbachia strain to wVulC that does not induce feminization, and compared it to the wVulC genome. Then, we performed gene expression profiling of the 216 resulting wVulC candidate genes throughout host developmental stages in A. vulgare and the heterologous host C. convexus. We identified a set of 35 feminization candidate genes showing differential expression during host sexual development. Interestingly, 27 of the 35 genes are present in the f element, which is a piece of a feminizing Wolbachia genome horizontally transferred into the nuclear genome of A. vulgare and involved in female sex determination. Assuming that the molecular genetic basis of feminization by Wolbachia and the f element is the same, the 27 genes are candidates for acting as master sex determination genes in A. vulgare females carrying the f element.
Highlights
Sex determination is a key biological pathway which governs the sexual differentiation of an individual into a male or female and its ability to produce male or female gametes
We identified a set of 35 feminization candidate genes showing differential expression during host sexual development
We identified a set of 35 candidate genes out of the 1888 wVulC genes that may be implicated in feminization induced by Wolbachia wVulC in the host A. vulgare, two of which appear to be promising
Summary
Sex determination is a key biological pathway which governs the sexual differentiation of an individual into a male or female and its ability to produce male or female gametes. Development as either a male or female is a generally conserved feature in animals, there is an amazing diversity of modes of sex determination [1,2]. The most common mode of sex determination is genotypic sex determination, in which nuclear genetic elements control sex determination. Prime examples of genotypic sex determination are sex chromosomes, i.e., chromosomes that carry sex-determining factors. The second mode of sex determination is environmental sex determination, in which external stimuli control sex determination. Environmental sex determination is defined here in
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