ABSTRACT
When the first group of DNA puffs is active in the salivary gland regions S1 and S3 of Bradysia hygida larvae, there is a large increase in the production and secretion of new salivary proteins demonstrable by [3H]-Leu incorporation. The present study shows that protein separation by SDS-PAGE and detection by fluorography demonstrated that polypeptides range in molecular mass from about 23 to 100 kDa. Furthermore, these proteins were synthesized mainly in the S1 and S3 salivary gland regions where the DNA puffs C7,C5,C4 and B10 are conspicuous, while in the S2 region protein synthesis was very low. Others have shown that the extent of amplification for DNA sequences that code for mRNA in the DNA puffs C4 and B10 was about 22 and 10 times, respectively. The present data for this group of DNA puffs are consistent with the proposition that gene amplification is necessary to provide some cells with additional gene copies for the production of massive amounts of proteins within a short period of time (Spradling AC and Mahowald AP (1980) Proccedings of the National Academy of Sciences, USA, 77: 1096-1100).
Subject(s)
Animals , Female , Diptera/genetics , DNA Probes/genetics , Gene Amplification/genetics , In Vitro Techniques , Peptides/biosynthesis , Salivary Glands/physiology , Saliva/chemistry , Electrophoresis , Electrophoresis, Polyacrylamide Gel , RadioactivityABSTRACT
A recombinant clone carrying a 2-kb fragment was isolated from a mini-library of the B10 DNA puff of Bradysia hygida. This fragment was amplified in the salivary gland during the period of DNA puff formation. Amplification started when DNA puff anlage was formed and continued to increase, reaching a maximum of abouth 10-fold 28 h later. Northern blot hybridization experiments showed that this 2-kb fragment was complementary to two RNA species of about 1.3 kb and 1.1 kb, which are developmentally regulated in the salivary gland. Maximum amounts of these messages were present when the B10 puff is fully expanded