Synthesis of Only Two Heat Shock Proteins Is Required for Thermoadaptation in Cultured Cowpea Cells

Cell cultures of a heat sensitive genotype of cowpea (Vigna unguiculata) were adapted to tolerate moderate levels of heat by maintaining cells at 32, 36, and 38 degrees C over many cell generations. Cells adapted to 32 and to 36 degrees C did not produce the typical heat shock proteins (HSP). Cells adapted to 38 degrees C synthesized two new proteins, which appear to be a subset of the HSP. In many temperature sensitive organisms it is thought that HSP confer thermotolerance. However, we hypothesize that specific proteins are associated with heat tolerance in cowpea, other heat tolerant plants (species such as sorghum and millet), and adapted cells which provide them with enhanced heat tolerance. From present data we suggest two proteins (70 and 80 kilodaltons) are strongly associated with heat tolerance and heat adaptation.