Promoter-directed expression of recombinant fire-fly luciferase in the salivary glands of Hermes-transformed Aedes aegypti.

Molecular genetic analyses of biological properties characteristic of insect vectors of disease, such as hematophagy and competence for pathogens, require the ability to isolate and characterize genes involved in these processes. We have been working to develop molecular approaches for studying the promoter function of genes that are expressed specifically in the adult salivary glands of the yellow fever mosquito, Aedes aegypti. Genomic DNA fragments containing cis-acting promoter elements from the Maltase-like I (MalI) and Apyrase (Apy) genes were cloned so as to direct the expression of the reporter gene, luciferase (luc). The function of the promoters was assayed transiently in cultured insect cells and by germ-line transformation of Ae. aegypti. MalI and Apy DNA fragments consisting of at least 650 nucleotides (nt) of DNA immediately adjacent to the 5'-end of the initiation codon of the mosquito genes directed constitutive expression of the luc reporter gene in cultured cells. When introduced into Ae. aegypti chromosomes, approximately 1.5 kilobases (kb) of each promoter were able to direct the predicted developmental-, sex- and tissue-specific expression of the reporter gene in patterns identical to those determined for the respective endogenous genes.