Int. J. Dev. Biol. 53: 109 - 120 (2009)

https://doi.org/10.1387/ijdb.082681ms

Vol 53, Issue 1

Ceratitis capitata transformer-2 gene is required to establish and maintain the autoregulation of Cctra, the master gene for female sex determination

Original Article | Published: 1 December 2008

Marco Salvemini¹, Mark Robertson², Benjamin Aronson², Peter Atkinson², Lino C. Polito^1,3 and Giuseppe Saccone*^,1

¹Department of Biological Sciences, Section of Genetics and Molecular Biology, University of Naples “Federico II”, Naples, Italy, ²Department of Entomology, University of California, Riverside, CA, USA and ³Institute of Genetics and Biophysics “A. Buzzati-Traverso”, Naples, Italy

Abstract

In Drosophila melanogaster, transformer-2 (TRA-2) which is a non-sex-specific auxiliary splicing factor, is required to promote female sexual differentiation by interaction with the female-specific TRA. The two proteins positively regulate the splicing of both doublesex (dsx) and fruitless (fru) pre-mRNAs, which in turn regulate phenotypic and behavioural sexual dimorphism. In the Mediterranean fruitfly Ceratitis capitata, the female-specific CcTRA is similarly required not only for Ccdsx splicing, but also to exert a novel autoregulatory function that consists of promoting female-specific splicing of Cctra pre-mRNA. This study reports the isolation and functional analysis of the C. capitata homologue of the Drosophila transformer-2 gene (Cctra-2). Transient RNAi against Cctra-2 during embryonic development causes the full sex reversal of XX flies in adult fertile pseudo-males, as well as changes in the splicing pattern of Cctra, Ccdsx and Ccfruitless (Ccfru). We propose that: 1) Cctra-2, as in Drosophila, is necessary for promoting Ccdsx and putative Ccfru pre-mRNA female-specific splicing and that 2) unlike in Drosophila, Cctra-2 appears to be necessary for establishing female sex determination in early XX embryos and for maintaining the positive feedback regulation of Cctra during development.

Keywords

sex determination, Drosophila, Ceratitis, alternative splicing, autoregulation