Transcription and translation of heat shock and normal proteins in seedlings and developing seeds of soybean exposed to a gradual temperature increase

Abstract

Heat shock proteins (hsps) are synthesized at higher temperatures in soybean seedlings exposed to a gradual temperature increase as compared to a rapid heat shock (hs). There are differences in the pattern of synthesis of different hsps depending on whether the temperature exposure is rapid or gradual. The synthesis of normal temperature proteins also occurs at higher temperatures after a gradual increase in temperature than after a rapid hs. The increased protein synthesis seen with a gradual temperature increase is because of increased mRNA levels. In general the mRNAs for actin and the hsps are found at temperatures 6 to 9°C higher after a gradual temperature increase than after a rapid hs. While hsps are detected in developing seeds after either type of heat treatment an increase in the synthesis of hsps is observed at the higher temperatures after a gradual temperature increase compared to a rapid hs to the same temperatures. The only proteins synthesized at the highest temperatures (49°C) after a gradual temperature increase are the precursors of the storage proteins and the hsps. After a gradual increase in temperature the mRNAs for the 11S storage proteins are present in relatively large amounts up to 43°C decreasing thereafter but were detectable at 52°C; whereas, the hsp mRNA levels were relatively constant from 40 to 52°C.