Towards the analysis of transcriptome from sexed Ceratitis capitata embryos: how to produce XX male embryos by transgene-mediated RNAi and identify male biased/male determining genes.

In the agricultural pest Ceratitis capitata, the Mediterranean fruitfly (Medfly), the sex determination is controlled by a Y-linked male determining factor (M-factor) which influences either directly or indirectly the state of activity of the female determining master gene Cctraep (Cctra epigenetic) at 5-7 hours  of oviposition. We have developed a Ceratitis transgenic sexing strain which produces male-only progeny (95% efficiency) by transgene-mediated RNAi against the female determiner Cctraep gene. C. capitata XX males are fully fertile and could be successfully mated with XX females thus leading to the production of female-only (XX) progeny. We have prepared polyA+ RNA from XX embryos and from mixed XY-XX embryos, both collected at 5-7 hours from oviposition. We have used a molecular subtractive approach to identify differentially expressed genes in XY versus XX at embryonic stages. We will outline  the molecular strategy employed to approach this scientific problem and preliminary data describing the identification of 8 male-biased cDNA positive clones presently under analysis. We started in parallel a transcriptome analysis of the two samples to approach the identification of male-biased genes/male-determining genes by an in silico subtractive analysis.