Two medfly promoters that have originated by recent gene duplication drivedistinct sex, tissue and temporal expression patterns

Genes encoding predominantly male-specific serum polypeptides (MSSPs) in th e medfly Ceratitis capitata are members of a multigene family that are stru cturally similar to the genes encoding odorant binding proteins of insects. To study the transcriptional regulation of the genes MSSP-alpha 2 and MSSP -beta 2 overlapping fragments of their promoters, containing the 5' UTRs an d 5' flanking regions, were fused to the lacZ reporter gene and introduced into the medfly genome via Mines-mediated germline transformation. Transgen ic flies were functionally assayed for beta-galactosidase activity. Despite their extensive sequence similarity, the two gene promoters show distinct expression patterns of the reporter gene, consistent with previously report ed evidence for analogous transcriptional activity of the corresponding end ogenous genes. The MSSP-alpha 2 promoter drives gene expression specificall y in the fat body of the adult males, whereas the MSSP-beta 2 promoter dire cts gene expression in the midgut of both sexes. In contrast, similar trans formation experiments in Drosophila melanogaster showed that both promoters drive the expression of the reporter gene in the midgut of adult flies of both sexes. Thus, the very same MSSP-alpha 2 promoter fragment directs expr ession-in the adult male fat body in Ceratitis, but in the midgut of both s exes in Drosophila. Our data suggest that through the evolution of the MSSP gene family a limited number of mutations that occurred within certain cis -acting elements, in combination with new medfly-specific trans-acting fact ors, endowed these recently duplicated genes with distinct sex-, tissue-, a nd temporal-specific expression patterns.