2 INDEPENDENT CIS-ACTING ELEMENTS REGULATE THE SEX-SPECIFIC AND TISSUE-SPECIFIC EXPRESSION OF YP3 IN DROSOPHILA-MELANOGASTER

In Drosophila, the three yolk protein (yp) genes are transcribed in a sex-, tissue- and developmentally specific manner, providing an ideal system in which to investigate the factors involved in their regulatio n. The yolk proteins are synthesized in the fat body of adult females, and in the ovarian follicle cells surrounding the developing oocyte d uring stages 8-10 of oogenesis. We report here an analysis of the yolk protein 3 (yp3) gene and its flanking sequences by means of P-element mediated germ-line transformation and demonstrate that a 747 bp promo ter region is sufficient to direct sex-specific expression in the fema le fat body and both the temporal- and cell-type-specific ficity of ex pression during oogenesis. Two elements that independently govern yp3 transcription in these tissues have been separated and no other sequen ces in the upstream, downstream or coding regions have been identified that are autonomously involved in yp3 expression.