Drosophila salivary gland proteins and pupation

Abstract

Pulse-labeling experiments of salivary glands from the prepupal stages of development showed selectively high rates of synthesis of a set of low molecular weight proteins (6K-12K). These proteins are stably maintained in the salivary glands during prepupal development and are subsequently transported to the pupation fluid (found between the pupal case and the prepupal cuticle) when pupation occurs. These small polypeptides are very basic with the major components having isoelectric points of 8.6-8.7 and the minor components having isoelectric points of 9.1-9.5. This study shows the continuing function of the salivary glands-specifically, the synthesis and secretion of a set of proteins with a putative role in pupation.

Apocrine Secretion in Drosophila Salivary Glands: Subcellular Origin, Dynamics, and Identification of Secretory Proteins

“…We suspect that this process is the same as one described by Sarmiento and Mitchell [123], called the salivary glands “second secretory cycle“. This non-canonical secretion occurs 4 to 6 hr prior to the period, 14 to 16 hr APF, during which salivary glands undergo PCD [47], [52], [124]–[126].…”

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

“…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).…”

A Kunitz type protease inhibitor related protein is synthesized in Drosophila prepupal salivary glands and released into the moulting fluid during pupation

“…Due to the availability of a putative electrophoretic mutant of the KIL-1 protein, we could test for the presumption that prepupal salivary gland proteins contribute to the pupation fluid, which covers the external surface of the pupating animal (Mitchell et al, 1977b;Sarmiento and Mitchell, 1982). Samples of the wildtype pupation fluid were collected and the proteins analysed by SDS-PAGE.…”

“…The presence of predominant low molecular weight components among prepupal salivary gland proteins has been demonstrated in various Drosophila species (Mitchell et al, 1977b;Kress, 1982;Sarmiento and Mitchell, 1982;Shirk et al, 1988). Hence, they might be major representatives of prepupal salivary gland function.…”