A shut-down in expression of an insulin-like peptide, ILP-1, halts ovarian maturation during the overwintering diapause of the mosquito Culex pipiens.
Short day-length is used to programme adult diapause in the mosquito, Culex pipiens. The downstream endocrine event that halts ovarian maturation is a shut-down in juvenile hormone (JH) production, and recent evidence suggests that the insulin signalling pathway may be a key upstream player in executing this developmental arrest. Genes encoding insulin-like peptides-1, -2 and -5 were identified in C. pipiens, and we report that transcript levels of insulin-like peptides-1 and -5 were significantly lower in diapausing females than in their nondiapausing counterparts. Genes encoding both insulin-like peptides-1 and -5 were suppressed using RNA interference in mosquitoes programmed for nondiapause, and ovarian maturation was monitored. Knocking down insulin-like peptide-1 with RNAi in nondiapausing mosquitoes resulted in a cessation of ovarian development akin to diapause, and this arrest in development could be reversed with an application of JH. Knocking down insulin-like peptide-5 did not alter ovarian development. These results are consistent with a role for insulin-like peptide-1 in the signalling pathway leading from the perception of short day-lengths to the shut-down in JH production that characterizes adult diapause in C. pipiens.
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Department of Entomology, Ohio State University, Columbus, USA.
Denlinger
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D000818:Animals; D003465:Culex / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D007605:Juvenile Hormones / Q000378:metabolism; D008969:Molecular Sequence Data; D010053:Ovary / Q000254:growth & development; D034622:RNA Interference; D012621:Seasons; D015398:Signal Transduction
D019476:Insect Proteins; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D007605:Juvenile Hormones