MOLECULAR-CLONING AND EXPRESSION OF A HEXAMERIN CDNA FROM THE MALARIAMOSQUITO, ANOPHELES-GAMBIAE

During the last larval instar, dipteran insects synthesize two hexamer ins rich in aromatic residues, typified by the larval serum proteins 1 and 2 (LSP-1 and LSP-2) of Drosophila melanogaster. We report here th e characterization of a complete cDNA sequence encoding a LSP-1-like p rotein from a lower dipteran insect, the malaria mosquito Anopheles ga mbiae. The cDNA encodes the subunit of a homohexamer, A. gambiae hexam erin-1.1 (AgHex-1.1), which is a major pupal protein but only a minor constituent of late larval hemolymph. AgHex-1.1 is moderately rich in methionine (3.9%) and particularly rich in aromatic residues (21% Phe + Tyr). Cytogenetic analysis reveals AgHex-1.1 to be encoded by a sing le-copy gene localized to division 22F within the proximal 2La inversi on breakpoint of chromosome 2 of A. gambiae. The AgHex-1.1 transcript is first detected in fourth-instar larvae (L4) and disappears abruptly in early pupae. In situ hybridization shows accumulation of the trans cript uniquely in the larval fat body. AgHex-1.1 mRNA is re-expressed in male and female adults at about 10% of the L4 level, with no effect of bloodfeeding in females. The potential roles of AgHex-1.1 in Anoph eles development and reproductive maturation are discussed.