Turnover of transfer RNA species during development of the posterior sikgland of Bombyxmori L.

Abstract

Quantitative changes in total tRNA and in five individual tRNA species have been studied in the developing posterior silkgland during the fifth larval instart of the silkworm Bombyxmori L. Using starvation and refeeding of the larvae at two distinct physiological stages — growth and secretion phases — half-lives and syntehsis rates of tRNAs have been estimated. Half-life times are roughly similar for all tRNA species examined (130 h for tRNA Ser, 100 h for tRNA Asp, 97 h for tRNA Gly, 92 h for tRNA Ala and 70 h for tRNA Thr) while the rates of synthesis vary widely according to the intracellular levels of each tRNA species. Ouu results suggests that the adaptation of individual tRNA species takes place at the transcriptional level or at the pre-tRNA maturation level. They rule out a regulatory mechanism through a selective degradation of mature tRNA species.