TERMINATION OF QUIESCENCE IN CRUSTACEA: THE ROLE OF TRANSFER RNA AMINOACYLATION AND INTRACELLULAR PH IN THE BRINE SHRIMP ARTEMIA
G.M.C. Janssen, M. Brandsma, W. Moller
Abstract:
Upon resumption of development of quiescent embryos of the brine shrimp Artemia the charging level of individual transfer RNAs increased in vivo, concomitant with the onset of protein synthesis. After one hour of development at 27 C, partial charging of most transfer RNAs was observed using quiescent embryos previously hydrated in the cold. The level of transfer RNA charging rose dramatically from an average of 4% tot 50% within the 24 hours of development before hatching. Concerning the mechanism of recharging of transfer RNAs, we observed that the level of aminoacyl-tRNA synthetase increased during development. For instance, methionyl-tRNA synthetase rose no less than ten-fold. In the case of valyl-tRNA synthetase the increase was lower and correlated to the amount of its mRNA. Therefore, synthetases and their transcription are considered to be crucial parameters for the gradual animation of cryptobiotic Artemia embryos and deacylated tRNAs as the "hunger" signal which controls gene transcription.
(Department of Medical Biochemistry, Leiden University, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands)