Requirement of wingless signaling and engrailed action in the development and differentiation of the reproductive system in Drosophila

The segment polarity genes wingless (wg) and engrailed (en) have been shown to play important roles in pattern formation at different stages of Drosophila development in the thoracic imaginal discs. We have studied the patterns of expression of these genes in genital discs from wild type larvae, pupae and pharate adults and also from hetero-allelic mutant combinations of these genes. Our results suggest that these genes play vital roles in the normal development and differentiation of genital discs and gonads. In the absence of normal wg or en functions, the flies showed a complete lack of internal accessory reproductive organs and specific defects in the external genitalia. In addition, the testes in such males were small, rounded and with an abnormal cellular organization, although the ovaries in females appeared normal. Temperature shift experiments using the conditional mutant allele of wg, (wgIL-114) indicated a requirement of wg signaling from second instar onwards for normal development and differentiation of the accessory reproductive organs. Using a heat-shock allele (Hs-wg) we also show that the spatially regulated expression of wg as a pre-requisite for normal development and differentiation. Based on the expression patterns of en and hedgehog (hh) we suggest that even in the genital disc development and differentiation the action of en is mediated through hh.