Allatotropin in the Corpora Allata and Ovaries of Rhodnius prolixus: Probable in situ regulatory mechanisms

Abstract

ABSTRACTOriginally described by Sir V. Wigglesworth in the Chagas disease vector Rhodnius prolixus, Juvenile Hormones (JHs) play critical roles during growth and reproduction. The JH described by Wigglesworth is the JH III skipped bisepoxide (JHSB3), and its titer in hemolymph varies along the 4th larval instar molting cycle. Allatotropin (AT), was originally characterized based on its ability to induce the synthesis of the JHs by the corpora allata (CA) in Lepidoptera. Beyond this function, AT has proved to be a myoregulator. Indeed, AT modulates muscle contractions in the gut, dorsal vessel and reproductive tissues. The presence of AT in the CA of 4th instar larvae of R. prolixus and the related species Triatoma infestans was previously shown, suggesting that AT might be involved in the regulation of JH synthesis in triatominae. Furthermore, the existence of allatotropic cells in this gland in T. infestans was also shown. This neuron-like cells show cytoplasmic processes projecting deeply between the cells engaged with JH synthesis. By using RT-qPCR we studied now the expression of both, AT and its receptor in the CA/CC complex along the 4th instar molting cycle, and in the ovaries of adult females. The expression of AT in the CA is highest between days 3 to 5 after meal, correlating with Mev-K and PPMev-D, two enzymes involved in the mevalonate pathway, as well as with the peak of JHSB3 on day 6. The results show that AT transcript is also present in the ovary suggesting a myoregulatory paracrine mechanism of regulation. Finally, our data suggest the existence of in situ mechanisms in the CA and ovaries of R. prolixus involving AT in both JHs synthesis and muscle contraction.