Reassessing ecdysteroidogenic cells from the cell membrane receptors’ perspective

Abstract

Ecdysteroids secreted by the prothoracic gland (PG) cells of insects control the developmental timing of their immature life stages. These cells have been historically considered as carrying out a single function in insects, namely the biochemical conversion of cholesterol to ecdysteroids and their secretion. A growing body of evidence shows that PG cells receive multiple cues during insect development so we tested the hypothesis that they carry out more than just one function in insects. We characterised the molecular nature and developmental profiles of cell membrane receptors in PG cells of Bombyx mori during the final larval stage and determined what receptors decode nutritional, developmental and physiological signals. Through iterative approaches we identified a complex repertoire of cell membrane receptors that are expressed in intricate patterns and activate previously unidentified signal transduction cascades in PG cells. The expression patterns of some of these receptors explain precisely the mechanisms that are known to control ecdysteroidogenesis. However, the presence of receptors for the notch, hedgehog and wingless signalling pathways and the expression of innate immunity-related receptors such as phagocytosis receptors, receptors for microbial ligands and Toll-like receptors call for a re-evaluation of the role these cells play in insects.

Transcriptomic analysis of crustacean molting gland (Y-organ) regulation via the mTOR signaling pathway

“…Wnt (Fig. 6 ), an activator of mTORC1, has been implicated in ecdysteroidogenesis in the insect prothoracic gland 73 . These genes may undergo increased initial rates of transcription due to rapamycin treatment.…”

Combinatory annotation of cell membrane receptors and signalling pathways of Bombyx mori prothoracic glands

“…1) as described in a supporting paper 20 , 2) annotations of signalling pathways that are present in PG cells (Fig. 2), 3) annotations of Bombyx mori genes with the LocTree3 21 protein subcellular localisation prediction dataset (Data Citation 1) and 4) annotation of the coding sequences of the proteins (Data Citation 1), by integrating results of our bioinformatics, LC-MS/MS and RNA-seq analyses from PG samples from day 0 (V−0) and day 6 (V−6) of the 5th instar (Data Citation 1) and further analysis of the expression patterns of these receptors by quantitative PCR (qPCR).…”

“…Due to high sequence similarity between some transcripts a total of 30 genes could not be analysed by qPCR 20 . Of those 339 genes that were analysed by qPCR, 29 genes were found to be false negative, i.e., expressed in the PG cells (Table 1), mainly because their expression showed peaks on days other than day 0 (V−0) or day 6 (V−6) from which the RNA-seq and LC-MS/MS samples were derived.…”

Hedgehog promotes cell proliferation in the midgut of silkworm, Bombyx mori

“…BmCi is involved in the maintenance of micro‐compartment identity within the middle silk glands (Dhawan & Gopinathan, ). In the prothoracic gland of B. mori , five genes that encode proteins with high sequence similarity to Patch and one gene encoding Smo have been identified (Alexandratos et al ., ). However, the physiological roles of the BmHh signaling pathway in the midgut of B. mori remain unknown.…”