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

Abstract

Independent of the design of the life cycle of any insect, their growth and reproduction are highly choreographed through the action of two versatile hormones: ecdysteroids and juvenile hormones (JH). However, the means by which JH can target tissues and exert its pleiotropic physiological effects is currently still not completely elucidated. Although the identity of the one JH receptor is currently still elusive, recent evidence seems to point to the product of the Methoprene-tolerant gene (Met) as the most likely contender in transducing the action of JH. Studies on the role of this transcription factor have mostly been focused on immature insect stages. In this study we used the viviparous cockroach Diploptera punctata, a favorite model in studying JH endocrinology, to examine the role of Met during reproduction. A tissue distribution and developmental profile of transcript levels was determined for Met and its downstream partners during the first gonadotropic cycle of this cockroach. Using RNA interference, our study shows that silencing Met results in an arrest of basal oocyte development; vitellogenin is no longer transcribed in the fat body and no longer taken up by the ovary. Patency is not induced in these animals which fail to produce the characteristic profile of JH biosynthesis typical of the first gonadotropic cycle. Moreover, the ultrastructure of the follicle cells showed conspicuous whorls of rough endoplasmic reticulum and a failure to form chorion. Our study describes the role of Met on a cellular and physiological level during insect reproduction, and confirms the role of Met as a key factor in the JH signaling pathway.

Genomic and functional characterization of a methoprene-tolerant gene in the kissing-bug Rhodnius prolixus

“…In fact, it was recently shown that Met knockdown inhibits ovarian development in the cockroach D. punctata (Marchal et al, 2014). Our functional studies also confirmed the importance of RpMet for the normal reproductive maturation of adult females.…”

Juvenile hormone signaling – a mini review

“…In L . migratoria , JH signaling promotes endoreplication of adult fat body cells to prepare the female for vitellogenesis (Guo et al ., ; Song et al ., ; Wu et al ., ) and is indispensable for basal oocyte development (Marchal et al ., ). In P .…”

Physiology: Female Flies Have the Guts for Reproduction

“…Speech category learning is, a priori, a good candidate for a dedicated mechanism. Even though the inventories of speech categories are variable across languages, infants learn them quickly, reliably, and without formal supervision [5]. In contrast, past a critical period, they are very difficult to learn, as becomes evident when adults learn a second language [6].…”

“…JH is generated by the corpora allata and is essential to multiple physiological processes, including molting, metamorphosis, growth regulation, as well as egg production. Surgical removal of the corpora allata in grasshoppers and butterflies arrests egg development [4], as does ubiquitous knockdown of the JH receptor in cockroaches [5]. In Drosophila, starvation or perturbation of the insulin signaling pathway -a major regulator of the nutritional response in all animalsresults in a suppression of JH synthesis and reproductive diapause [6].…”