Rhythmic change of adipokinetic hormones diurnally regulates locust vitellogenesis and egg development

Abstract

Adipokinetic hormones (AKHs), the neurohormones synthesized in the insect corpora cardiaca are known to mobilize lipids and carbohydrates for energyconsuming activities including reproduction. However, both inhibitory and stimulatory effects of AKHs on insect reproduction have been reported, and the underlying mechanisms remain elusive. Using the migratory locust, Locusta migratoria, as a model system, we report here that AKHs are expressed in response to rhythmic diel change, and AKH III expression increases markedly at photophase. Diurnal injection of AKH III but not AKH I or AKH II in adult females stimulates vitellogenesis and egg development. In contrast, AKH treatment at scotophase represses female reproduction. RNA interference-mediated knockdown of AKH receptor (AKHR) results in significantly reduced vitellogenin (Vg) expression in the fat body at photophase along with reduced Vg deposition in the ovary. AKHR knockdown also leads to decreased expression of Brummer, triacylglycerol lipase and trehalose transporter, accompanied by suppressed mobilization of triacylglycerol and trehalose. We propose that in addition to stimulating Vg expression at photophase, AKH/AKHR signalling is likely to regulate ovarian uptake of Vg via triacylglycerol mobilization and trehalose homeostasis. This study provides new insights into the understanding of AKH/AKHR signalling in the regulation of insect reproduction.

Identification of G protein‐coupled receptors required for vitellogenesis and egg development in an insect with panoistic ovary

“…The gregarious colony of L. migratoria was reared under 14 : 10 L : D photoperiod and at 30 ± 2 °C at a density of ∼200 locusts in a well‐ventilated cage as previously described (Wu et al ., 2018; Zheng et al ., 2020). Wheat bran was continuously supplied and wheat seedlings were provided daily.…”

“…Protein extracts were isolated from the fat body, hemolymph and ovary of adult females at 8 d PAE, and quantified with a BCA protein assay kit (Applygen Technologies) as previously described (Zheng et al ., 2020). Western blots were performed using the antibodies against VgA (Luo et al ., 2017; Song et al ., 2018) and β‐actin (MBL), corresponding horseradish peroxidase‐conjugated secondary antibodies (CWBIO) and an enhanced chemiluminescent reagent (CWBIO).…”

Juvenile hormone acts through FoxO to promote Cdc2 and Orc5 transcription for polyploidy-dependent vitellogenesis

“…Total RNA was extracted from fat bodies using Trizol reagent (Tiangen) as previous reported (Wang et al, 2017;Wu et al, 2018;Zheng et al, 2020). cDNA was reverse-transcribed using FastQuant RT Kit with gDNase (Tiangen).…”

Knockdown of the Halloween Genes spook, shadow and shade Influences Oocyte Development, Egg Shape, Oviposition and Hatching in the Desert Locust

“…To further investigate this, the effect of knocking down the Halloween genes on transcript levels of SchgrMet and SchgrKr - h1 was investigated using qRT-PCR. Both genes were previously indicated to be a good measure for the activity of JH [ 76 , 77 , 78 , 79 ]. Furthermore, transcript levels of SchgrVg1 and SchgrVg2 after knockdown of the different Halloween genes, separately and in combination, were investigated to evaluate the effect on vitellogenin synthesis.…”