The acquisition of thermal tolerance in larvae of Calpodes ethlius (Lepidoptera) and the in situ and in vitro synthesis of heat-shock proteins

Abstract

Larvae of Calpodes ethlius (Lepidoptera) reared at 22 °C die after 1 h at 45 °C, but they acquire the ability to tolerate 1 h at 45 °C if they are first exposed to 37 °C for 1 or 2 h. Incubation of intact larvae at 37 °C for 1 h induces the new and (or) enhanced synthesis of a similar family of polypeptides (relative masses (Mrs) ~ 22 000) in all tissues examined (silk gland, fat body, wing discs, central nervous system, and muscle). When these same tissues are cultured at 37 °C for 1 h, the new and (or) enhanced synthesis of at least 5 polypeptides (Mrs ~ 95 000, 81 000, 74 000, 26 000, and 22 000) is evident. The more dramatic response elicited from cultured tissues by heat shock results, presumably, from the added stress of dissection. The new and (or) enhanced synthesis of polypeptides with Mrs of ~22 000 by tissues of intact larvae, incubated at 37 °C for 1 h, may be related to the acquisition of thermal tolerance by similarly treated larvae. These results suggest that the induced synthesis of these polypeptides is an integral part of a ubiquitous molecular mechanism involved in the development of thermal tolerance.