The prepupal salivary glands of Drosophila melanogaster

Abstract

Evidence is presented in support of the concept that the larval salivary gland of Drosophila melanogaster continues to function as an important secretory organ throughout prepupal stages and after pupation. Just after puparium formation, and at other later periods, the glands appear to be in the process of disintegration, but each time they recover until after pupation. Nuclear blebbing occurs through the time of survival of the glands, but is shown not to involve transport of RNA out of the nucleus. Transport in and out of the nucleus is clearly rapid and in a steady state as compared to the massive and intermittent export of cytoplasmic substance into the lumen of the gland.

The timing of Drosophila salivary gland apoptosis displays an l(2)gl-dose response

“…Following secretion of the glue granules, the cytoskeletal proteins become first uniformly distributed in the cytoplasm of the salivary glands cells and then are gradually released in the lumen of the glands through a process which apparently leaves the cells intact, albeit strongly vacuolated. The release of these proteins appears to correspond to the second secretory cycle noticed by Mitchell et al 61 Surprisingly, after the release of the cytoskeletal components, the l(2)gl +t24 salivary gland cells which are essentially depleted of p127 and myosin-II retain however an apparent normal size and shape for several hours, albeit without regaining a normal cytoplasmic structure. In these glands, final histolysis occurs at least 12 h after the formation of cytoplasmic vacuoles.…”

“…In wild-type prepupae the disintegration of the salivary glands occurs relatively suddenly, 12 ± 13 h after the onset of pupariation 11,12,20,61,87 and cell death takes place in a nearly synchronous manner in all larval cells. Our investigations show that this process can be studied in vivo with the analytical achievement of a tissue culture system while maintaining the physiological relevance of an intact organism.…”

Expression of the Scavenger Receptor Class B type I (SR-BI) family in Drosophila melanogaster

“…Later, the larvae empty their gut, synthesize high levels of ecdysone and will enter into pupariation. We selected these as 120 h AEL clear-gut larvae and corroborated that already received the ecdysone pulse after dissection according to the morphology of their salivary glands (Mitchell et al, 1977). We focused our analysis in the steroidogenic tissues such as PG, ovaries and testes.…”

Mutations in a steroid hormone-regulated gene disrupt the metamorphosis of internal tissues in Drosophila: salivary glands, muscle, and gut

“…During mid-to-late third larval instar the salivary glands synthesize and secrete glycoproteins (Korge 1975;Zhimulev and Kolesnikov 1975;Beckendorf and Kafatos 1976;Boyd and Ashburner 1977), which serve as a "glue" to attach the animal to its substrate during the ensuing metamorphosis (Fraenkel and Brookes 1953). During the subsequent prepupal stage, the salivary glands synthesize and secrete novel proteins of unknown function (von Gaudecker and Schmale 1974;Harrod and Kastritis 1972;Korge 1977;Mitchell et al 1977;Zhimulev etal. 1981;Sarmiento and Mitchell 1982).…”

“…Over a period of several hours, beginning around the time of pupation, the prepupal salivary glands are destroyed in a distal-to-proximal manner by autolysis and phagocytosis (Bodenstein 1943;Harrod and Kastritis 1972;von Gaudecker 1972;von Gaudecker and Schmale 1974;Mitchell et al 1977). Degenerating salivary glands have a characteristic histological appearance, including progressive vacuolation, fragmentation, pycnotic nuclei and reduction in bulk (von Gaudecker 1972).…”