Starvation increases insulin sensitivity and reduces juvenile hormone synthesis in mosquitoes.
BACKGROUND
The interactions between the insulin signaling pathway (ISP) and juvenile hormone (JH) controlling reproductive trade-offs are well documented in insects. JH and insulin regulate reproductive output in mosquitoes; both hormones are involved in a complex regulatory network, in which they influence each other and in which the mosquito's nutritional status is a crucial determinant of the network's output. Previous studies reported that the insulin-TOR (target of rapamacyn) signaling pathway is involved in the nutritional regulation of JH synthesis in female mosquitoes. The present studies further investigate the regulatory circuitry that controls both JH synthesis and reproductive output in response to nutrient availability.


METHODS
We used a combination of diet restriction, RNA interference (RNAi) and insulin treatments to modify insulin signaling and study the cross-talk between insulin and JH in response to starvation. JH synthesis was analyzed using a newly developed assay utilizing fluorescent tags.


CONCLUSIONS
Our results reveal that starvation decreased JH synthesis via a decrease in insulin signaling in the corpora allata (CA). Paradoxically, starvation-induced up regulation of insulin receptor transcripts and therefore "primed" the gland to respond rapidly to increases in insulin levels. During this response to starvation the synthetic potential of the CA remained unaffected, and the gland rapidly and efficiently responded to insulin stimulation by increasing JH synthesis to rates similar to those of CA from non-starved females.
Department of Biological Sciences, Florida International University, Miami, Florida, United States of America.
Meritxell
M
Perez-Hedo
Department of Biological Sciences, Florida International University, Miami, Florida, United States of America.
Crisalejandra
C
Rivera-Perez
Department of Biological Sciences, Florida International University, Miami, Florida, United States of America.
Fernando G
FG
Noriega
D000330:Aedes / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D003335:Corpora Allata / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes; D005786:Gene Expression Regulation; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007333:Insulin Resistance; D007605:Juvenile Hormones / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011972:Receptor, Insulin / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D012098:Reproduction / Q000235:genetics; D015398:Signal Transduction; D013217:Starvation
D005456:Fluorescent Dyes; D007328:Insulin; D007605:Juvenile Hormones; D034741:RNA, Small Interfering; D011972:Receptor, Insulin