Juvenile hormone regulation of female reproduction in the common bed bug, Cimex lectularius

Abstract

To begin studies on reproduction in common bed bug, Cimex lectularius, we identified three genes coding for vitellogenin (Vg, a protein required for the reproductive success of insects) and studied their hormonal regulation. RNA interference studied showed that expression of Vg3 gene in the adult females is a prerequisite for successful completion of embryogenesis in the eggs laid by them. Juvenile hormone (JH) receptor, Methoprene-tolerant (Met), steroid receptor coactivator (SRC) and GATAa but not ecdysone receptor (EcR) or its partner, ultraspiracle (USP) are required for expression of Vg genes. Feeding and mating working through Vg, Met, SRC, EcR, and GATAa regulate oocyte development. Knockdown of the expression of Met, SRC, EcR, USP, BR-C (Broad-Complex), TOR (target of rapamycin), and GATAa in female adults resulted in a reduction in the number eggs laid by them. Interestingly, Kruppel homolog 1 (Kr-h1) knockdown in the adult females did not reduce their fecundity but affected the development of embryos in the eggs laid by females injected with Kr-h1 double-stranded RNA. These data suggest that JH functioning through Met and SRC regulate both vitellogenesis and oogenesis in C. lectularius. However, JH does not work through Kr-h1 but may work through transcription factors not yet identified.

Methoprene-Tolerant (Met) Is Indispensable for Larval Metamorphosis and Female Reproduction in the Cotton Bollworm Helicoverpa armigera

“…The expression of Vg, the major yolk protein in oocyte, is regulated by JH via its receptor Met, which has been documented in A. aegypti ( Raikhel et al, 2005 ; Zou et al, 2013 ), P. apterus ( Smykal et al, 2014 ), and T. castaneum ( Parthasarathy et al, 2010 ). Other studies in Cimex lectularius ( Gujar and Palli, 2016 ) and Nilaparvata lugens ( Lin et al, 2015 ) also confirmed that Met was required for Vg expression and ovarian development. Our RNAi experiment revealed that knockdown of HaMet resulted in the significant decline of Vg expression in the fat body, the reduced expression of VgR in the ovary, and the atrophied ovaries with less yolk protein deposition.…”

Dissecting the role of Krüppel homolog 1 in the metamorphosis and female reproduction of the cotton bollworm, Helicoverpa armigera

“…In addition, in our study the fecundity of Kr‐h1 ‐depleted adults was reduced. Interestingly, knockdown of Kr‐h1 in female adults of Cimex lectularius did not reduce their fecundity but affected the development of their embryos (Gujar & Palli, ). Taken together, these studies demonstrate that there are some differences amongst insect species in the mechanisms by which the JH signalling pathway regulates vitellogenesis and ovarian development.…”

The microRNAs let-7 and miR-278 regulate insect metamorphosis and oogenesis by targeting the juvenile hormone early-response gene Krüppel-homolog 1

“…In the mosquito Aedes aegypti, Kr-h1 can activate and repress the expression of its target genes for previtellogenic development and egg production in response to JH (Ojani et al, 2018;Shin et al, 2012;Zou et al, 2013). Depletion of Kr-h1 in adult females of the common bed bug Cimex lectularius does not reduce the egg number but severely reduces the egg hatchability (Gujar and Palli, 2016). In the migratory locust Locusta migratoria, Kr-h1 mediates JH action to promote vitellogenesis, ovarian development and oocyte maturation (Song et al, 2014).…”