Pupal Ecdysteroids Review final version.pdf (619.73 kB)
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Rethinking the ecdysteroid source during Drosophila pupal–adult development

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preprint
posted on 18.08.2022, 22:59 authored by Jack ScanlanJack Scanlan, CHARLES ROBINCHARLES ROBIN, Christen MirthChristen Mirth

Manuscript preprint for a review article to be submitted to a peer-reviewed journal. 

Authors

Jack L Scanlan1*, Charles Robin1, Christen Mirth2

Affiliations 

1 School of BioSciences, The University of Melbourne, Parkville Campus, Melbourne, Victoria, 3010, Australia

2 School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia

* Corresponding author

Email: jacksca@gmail.com 

Abstract

Ecdysteroids, typified by 20-hydroxyecdysone (20E), are essential hormones for the development, reproduction and physiology of insects and other arthropods. For over half a century, the vinegar fly Drosophila melanogaster has been used as a model of ecdysteroid biology, with many aspects of the biosynthesis and regulation of ecdysteroids understood at the molecular level, particularly with respect to their secretion from the prothoracic gland (PG) cells of the ring gland, widely considered the dominant biosynthetic tissue during development. Discrete pulses of 20E orchestrate transitions during the D. melanogaster life cycle, the sources of which are generally well understood, apart from the large 20E pulse at the onset of pharate adult development, which has received little recent attention. As the source of this pharate adult pulse (PAP) is a curious blind spot in Drosophila endocrinology, we evaluate published biochemical and genetic data as they pertain to three hypotheses for the source of PAP 20E: the PG; an alternative biosynthetic tissue; or the recycling of stored 20E. Based on multiple lines of evidence, we contend the PAP cannot be derived from biosynthesis, with other data consistent with D. melanogaster able to recycle ecdysteroids before and during metamorphosis. Further experimental work is required to test the ecdysteroid recycling hypothesis, which would establish fundamental knowledge of the function, regulation and evolution of metamorphic hormones in insects. 

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