Heat shock proteins of higher plants

The pattern of protein synthesis changes rapidly and dramatically when the growth temperature of soybean seedling tissue is increased from 28°C (normal) to about 40°C (heat shock). The synthesis of normal proteins is greatly decreased and a new set of proteins, “heat shock proteins,” is induced. The heat shock proteins of soybean consist of 10 new bands on one-dimensional NaDodSO4 gels; a more complex pattern is observed on two-dimensional gels. When the tissue is returned to 28°C after 4 hr at 40°C, there is progressive decline in the synthesis of heat shock proteins and reappearance of a normal pattern of synthesis by 3 or 4 hr.In vitro translation of poly(A)+ RNAs isolated from tissues grown at 28 and 40°C shows that the heat shock proteins are translated from a new set of mRNAs induced at 40°C; furthermore, the abundant class mRNAs for many of the normal proteins persist even though they are translated weakly (or not at all)in vivo at 40 or 42.5°C. The heat shock response in soybean appears similar to the much-studied heat shock phenomenon inDrosophila .