The insect transformer2 (tra2) gene has a prevalent role in cooperating with the sex-determining gene transformer (tra) to direct female differentiation. Here, we report the identification and characterization of Btau-tra2, the tra2 orthologue of the pumpkin fruit fly, Bactrocera tau, an invasive agricultural pest. The Btau-tra2 gene produces three transcript variants. However, only two transcripts can be examined; one is present at all developmental stages in the soma and germline of both sexes and the other one is specific to the embryo and the germline. Knocking down the function of Btau-tra2 produced a male-biased sex ratio and some intersexes. Consistent with a role in sex determination, the obtained intersexual and male sterility phenotypes express a mix of male and female splice variants of the tra and doublesex (dsx) orthologues, indicating that Btau-tra2 has a conserved splicing regulatory function and acts together with/upstream of tra and dsx. In addition, some males obtained from the knock down are fertile but their fertilities are extremely reduced. Moreover, almost all surviving RNA interference (RNAi) males harbour testes having some defects in their external morphologies. Most notably, the body size of a few surviving RNAi flies was two-to threefold increased with respect to the normal size. Our findings suggest that Btau-tra2 is involved in male fertility and may also have an unprecedented role in body size control besides its conserved role in sex determination.
http://www.eje.cz tein, TRA F , which combines with TRA2, a non sex-specifi c protein, generating the TRA/TRA2 complex protein. This protein complex regulates dsx splicing in the female mode to produce DSX F , which directs female embryonic development. In XY embryos that do not have the SXL protein, both tra and dsx genes produce male-specifi c proteins, TRA M and DSX M , which induce embryos to develop as male fl ies (Baker & Wolfner, 1988; Burtis & Baker, 1989; Hoshijima et al., 1991; Salz & Erickson, 2010). Sex determination cascades of other insects do, however, seem to be different from that of Drosophila. In tephritid insects for example, the Sxl genes identifi ed from Ceratitis capitata and Bactrocera oleae do not function in sex determination, although their Sxl sequences are highly similar to that of Drosophila (Saccone et al., 1998; Lagos et al., Identifi cation and characterization of doublesex from the pumpkin fruit fl y, Bactrocera tau (Diptera: Tephritidae
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