Aedes aegypti glutamine synthetase: expression and gene structure

The peritrophic, matrix (PM) is the first natural barrier a mosquito-borne parasite faces when ingested with a blood meal; consequently, understanding the biology of PM formation could provide novel transmission control strat egies. Because the PM is composed of chitin (a molecule of repeating units of N-acetyl glucosamine), glycoproteins and glucose, characterizing the reg ulation of enzymes involved in chitin production should provide information concerning factors that influence PM formation. We previously have shown t hat glutamine synthetase (GS) provides the glutamine needed in the initial steps of chitin biosynthesis in the yellow fever mosquito, Aedes aegypti. I n the present study we show that GS is encoded by a single 4.5 kb gene, des ignated inGS, containing three exons and two introns. Multiple transcripts are generated from mGS presumably by differential splicing of the introns. Sequences of two cDNAs encoding GS are identical at the protein level, but differ in their 5'-untranslated regions. GS message is constitutively expre ssed in all developmental stages and in most tissues, with an increase in G S transcription observed in midgut and fat body tissues of female mosquitoe s following a blood meal. Transcripts are localized to the apical side of t he mosquito midgut epithelium and data suggest that mGS transcription is re gulated by an Oct-1 transcription factor. (C) 2001 Elsevier Science B.V. Al l rights reserved.