FoxO inhibits juvenile hormone biosynthesis and vitellogenin production in the German cockroach

Abstract

The transcription factor Forkhead-box O (FoxO) is the main transcriptional effector of the Insulin Receptor/Phosphatidylinositol 3-kinase (InR/PI3K) pathway. In a situation of nutrient restriction, the pathway is inactive and FoxO translocates to the nucleus to exert its transcriptional action. In starved females of the cockroach Blattella germanica, the reproductive processes, and in particular the synthesis of juvenile hormone in the corpora allata and that of vitellogenin in the fat body, are arrested. In the present report we examine the possible role of FoxO in the transduction of the nutritional signals to these reproductive events. We first cloned FoxO cDNA from B. germanica (BgFoxO), and showed that its expression is not nutritionally regulated. BgFoxO knockdown using systemic RNAi in vivo in starved females elicited an increase of juvenile hormone biosynthesis, although without modifying mRNA levels of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase-1, HMG-CoA synthase-2, HMG-CoA reductase or methyl farnesoate epoxidase (CYP15A1) in corpora allata. In addition, BgFoxO RNAi treatment produced a remarkable increase of vitellogenin mRNA levels in fat body and of vitellogenin protein in the haemolymph. Our results indicate that BgFoxO plays an inhibitory role on juvenile hormone biosynthesis and vitellogenin production in a situation of nutrient shortage.

Juvenile hormone and insulin suppress lipolysis between periods of lactation during tsetse fly pregnancy

“…Suppression of FOXO significantly increased JHAMT expression, while reducing bmm expression (Figure 5a). Therefore, FOXO reduction increases JH biosynthesis through upregulation of JHAMT, as predicted by Suren-Castillo et al (2012). Since the promoter region of bmm was reported to harbor several FOXO response elements in Drosophila (Wang et al, 2011), reduction of bmm expression following FOXO reduction is not unexpected.…”

“…Recent studies show that the JH signaling may intersect with the IIS pathway through the Chico (an adaptor protein that interacts with the insulin-like peptide receptor) and/or FOXO (the downstream transcriptional regulator of the insulin pathway) proteins or may even directly alter the expression of specific ILPs (Parthasarathy and Palli, 2011; Sheng et al, 2011). Genetic suppression of chico or FOXO reduces or increases JH biosynthesis, respectively (Tu et al, 2005; Suren-Castillo et al, 2012). Unlike the IIS pathway, JH signaling is unique to insects.…”

Methoprene-Tolerant (Met) Knockdown in the Adult Female Cockroach, Diploptera punctata Completely Inhibits Ovarian Development

“…These effects could be rescued by injection of bovine insulin. Studies in the mosquito, Aedes aegypti and the cockroach, Blattella germanica , have demonstrated feedback of the ILP/TOR pathways on the JH biosynthetic activity of the CA, thus placing JH downstream of the ILP/TOR pathway [60]–[62]. In starved B. germanica , silencing FOXO resulted in increased Vg mRNA levels in the fat body and a rise in JH biosynthetic activity.…”

Interplay between insulin signaling, juvenile hormone, and vitellogenin regulates maternal effects on polyphenism in ants

“…10) suggest that the insulin/insulin-like growth factor signaling (IIS), JH, and vitellogenin (Vg) pathways, known to regulate reproduction in adult insects (47)(48)(49)(50)(51), play predominant roles in modulating larval development in response to environmental cues. A well-known example illustrating the role of these pathways is the caste fate of the female brood (queen or worker) in the honey bee Apis mellifera (52)(53)(54)(55)(56)(57)(58).…”