title: Insulin receptor-mediated nutritional signalling regulates juvenile hormone biosynthesis and vitellogenin production in the German cockroach.
abstract: Female reproductive processes, which comprise, amongst others, the synthesis of yolk proteins and the endocrine mechanisms which regulate this synthesis, need a considerable amount of energy and resources. The role of communicating that the required nutritional status has been attained is carried out by nutritional signalling pathways and, in particular, by the insulin receptor (InR) pathway. In the present study, using the German cockroach, Blattella germanica, as a model, we analysed the role of InR in different processes, but mainly those related to juvenile hormone (JH) synthesis and vitellogenin production. We first cloned the InR cDNA from B. germanica (BgInR) and then determined that its expression levels were constant in corpora allata and fat body during the first female gonadotrophic cycle. Results showed that the observed increase in BgInR mRNA in fat body from starved compared to fed females was abolished in those females treated with systemic RNAi in vivo against the transcription factor BgFoxO. RNAi-mediated BgInR knockdown during the final two nymphal stages produced significant delays in the moults, together with smaller adult females which could not spread the fore- and hindwings properly. In addition, BgInR knockdown led to a severe inhibition of juvenile hormone synthesis in adult female corpora allata, with a concomitant reduction of mRNA levels corresponding to 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase-1, HMG-CoA synthase-2, HMG-CoA reductase and methyl farnesoate epoxidase. BgInR RNAi treatment also reduced fat body vitellogenin mRNA and oocyte growth. Our results show that BgInR knockdown produces similar phenotypes to those obtained in starved females in terms of corpora allata activity and vitellogenin synthesis, and indicate that the InR pathway mediates the activation of JH biosynthesis and vitellogenin production elicited by nutrition signalling.
authors.affiliation: Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Abrisqueta
authors.affiliation: Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Songül
authors.initials: S
authors.lastname: Süren-Castillo
authors.affiliation: Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain. Electronic address: joseluis.maestro@ibe.upf-csic.es.
authors.forename: José L
authors.initials: JL
authors.lastname: Maestro
mesh_terms: D000818:Animals; D020048:Blattellidae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D003335:Corpora Allata / Q000201:enzymology / Q000378:metabolism; D005260:Female; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics / Q000378:metabolism; D006904:Hydroxymethylglutaryl-CoA Synthase / Q000235:genetics / Q000378:metabolism; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007605:Juvenile Hormones / Q000096:biosynthesis*; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014819:Vitellogenins / Q000096:biosynthesis*
chemical_list: D019476:Insect Proteins; D007605:Juvenile Hormones; D014819:Vitellogenins; D006903:Hydroxymethylglutaryl CoA Reductases; D006904:Hydroxymethylglutaryl-CoA Synthase; D011972:Receptor, Insulin
keywords: Blattella germanica; Insulin receptor; Juvenile hormone; Nutritional signalling; Vitellogenesis