SALIVARY GLAND SECRETION AND ITS RELATION TO CHROMOSOMAL PUFFING IN THE DIPTERAN, CHIRONOMUS THUMMI

Abstract

An analysis of the proteins of the salivary secretion of Chironomus thummi larvae has revelaed the presence of a number of enzymes and antigens. These enzymes and antigens are indistinguishable from a number of constituents also present in the insect''s blood and in other tissues. None of the major protein components of the secretion that we have detected are tissue-specific in the sense of being unique to the salivary gland cells. By injecting isotopically labeled proteins into the larval coelom, we could demonstrate that both hemolymph proteins and human serum albumin are taken up by the salivary gland cells and secreted in saliva. Autoradiographic techniques indicated that these proteins were taken up at the hemel border of the gland and were then incorporated into vesicles having the appearance of secretion granules. Transfer of protein seems to occur without degradation, since the human serum albumin retained its antigenic properties as well as its radioactivity. The secretory processes of the salivary gland appear to be intimately linked with the activities of tissue-specific puffs of the chromosomes, particularly with the largest of the puffs (the Balbiani rings). These findings indicate that the tissue-specific puffs are not related to the synthesis of specific constituents of the salivary secretion. The possibility is suggested that the puffs are associated with the selective uptake, concentration, and release of the secretion.