Heat shock induced proteins in plant cells

Abstract

Abstract Tobacco (Nicotiana tabacum) and soybean (Glycine max) tissue culture cells were exposed to a heat shock and protein synthesis studied by SDS‐polyacrylamide gel electrophoresis after labeling with radioactive amino acids. A new pattern of protein synthesis is observed in heat‐shocked cells compared to that in control cells. About 12 protein bands, some newly appearing, others synthesized in greatly increased quantities in heat‐shock cells, are seen. Several of the heat‐shock proteins (HSPs) in both tobacco and soybean are similar in size. One of the HSPs in soybean (76K) shares peptide homology with its presumptive 25°C counterpart, indicating that the synthesis of at least some HSPs may not be due to activation of new genes. The optimum temperature for maximal induction of most HSPs is 39–40°C. Total protein synthesis decreases as heat‐shock temperature is increased and is barely detectable at 45°C. The heat‐shock response is maintained for a relatively short time in tobacco cells. After 3 hr at 39°C, a decrease is seen in the synthesis of the HSPs, and after 4 hr practically no HSPs are synthesized. After exposure to 39°C for 1 hr, followed by a return of tobacco cells to 26°C, recovery to the control pattern of synthesis requires greater than 6 hours. These results indicate that cells of flowering plants exhibit a heat‐shock response similar to that observed in animal cells.