The juvenile hormone described in Rhodnius prolixus by Wigglesworth is juvenile hormone III skipped bisepoxide

Maria Jose Villalobos-Sambucaro,Francisco Fernandez-Lima,María Eugenia Alzugaray,Marcela Nouzova,Cesar E Ramirez,Jorge Rafael Ronderos,Fernando G Noriega

doi:10.1038/s41598-020-59495-1

Abstract

Juvenile hormones (JHs) are sesquiterpenoids synthesized by the corpora allata (CA). They play critical roles during insect development and reproduction. The first JH was described in 1934 as a “metamorphosis inhibitory hormone” in Rhodnius prolixus by Sir Vincent B. Wigglesworth. Remarkably, in spite of the importance of R. prolixus as vectors of Chagas disease and model organisms in insect physiology, the original JH that Wigglesworth described for the kissing-bug R. prolixus remained unidentified. We employed liquid chromatography mass spectrometry to search for the JH homologs present in the hemolymph of fourth instar nymphs of R. prolixus. Wigglesworth’s original JH is the JH III skipped bisepoxide (JHSB3), a homolog identified in other heteropteran species. Changes in the titer of JHSB3 were studied during the 10-day long molting cycle of 4th instar nymph, between a blood meal and the ecdysis to 5th instar. In addition we measured the changes of mRNA levels in the CA for the 13 enzymes of the JH biosynthetic pathway during the molting cycle of 4th instar. Almost 90 years after the first descriptions of the role of JH in insects, this study finally reveals that the specific JH homolog responsible for Wigglesworth’s original observations is JHSB3.

Highlights

We have previously described the potential of mass spectrometry (MS) based protocols for structural identification and quantification of Juvenile hormones (JHs) homologues from insect samples[11,12]
The changes in the titer of JHSB3 were measured in the hemolymph of R. prolixus 4th instar nymphs during the molting cycle, and quantitative real-time PCR studies revealed the changes of mRNA levels in the corpora allata (CA) for the 13 enzymes of the JH biosynthetic pathway during the molting cycle of 4th instar nymphs
The latter was operated under multiple reaction monitoring (MRM) mode, detecting fragmentation ions after collision-induced dissociation (CID)[13]

Summary

Introduction

The manuscripts contained a series of elegant studies, including a parabiosis techniques that allowed the mixing of the hemolymph of fourth and fifth instar nymphs, as well as corpora allata (CA) transplantation experiments. These studies permitted Wigglesworth to demonstrate for the first time the existence of an “inhibitory hormone” secreted by the CA and delivered to target tissues by the hemolymph. We reported on a liquid chromatography–mass spectrometry (LC-MS/MS) protocol for the identification and quantification of the five most common JH homologs[13] This protocol allows the detection of JH I, JH II, JH III, JH III bisepoxide (JHB3) and JH III skipped bisepoxide (JHSB3) in a single LC-MS/MS run. The changes in the titer of JHSB3 were measured in the hemolymph of R. prolixus 4th instar nymphs during the molting cycle, and quantitative real-time PCR (qRT-PCR) studies revealed the changes of mRNA levels in the CA for the 13 enzymes of the JH biosynthetic pathway during the molting cycle of 4th instar nymphs

Methods

Results

Discussion

Conclusion