Recombinant juvenile hormone esterase, an effective tool for modifying juvenile hormone-dependent expression of the early trypsin gene in mosquitoes

The study of the changes in the steady‐state levels of the early trypsin (ET) messenger RNA (mRNA) was used as a sensitive assay for measuring the effects of recombinant juvenile hormone esterase (rJHE) on juvenile hormone (JH)‐dependent gene expression in mosquitoes. ET is a female‐specific protease present in the midgut of the yellow fever mosquito Aedes aegypti during the first few hours after ingestion of a blood meal. Transcription of the early trypsin gene is part of the normal postemergence maturation of the midgut in the adult female, and it is regulated by JH. JHE was cloned from Heliothis virescens and expressed in a baculovirus vector. Injection of rJHE into mosquitoes resulted in an increase of JHE activity in the haemolymph. Injection of rJHE into newly emerged adult females delayed the normal increase in steady‐state levels of ET mRNA observed in controls. Topically applied methoprene (a JH analogue) reversed the effect of rJHE. Injection of increasing concentrations of rJHE into 3‐day‐old unfed females resulted in a dose‐dependent decrease in the steady‐state levels of ET mRNA after 24 h. The effect of rJHE was transient, once the enzyme was cleared (72 h after injection), the steady‐state levels of ET mRNA were restored. The injection of rJHE is an effective tool for modifying JH‐dependent expression of the early trypsin gene in mosquitoes.