Heat Shock Proteins in Tobacco Cell Suspension during Growth Cycle

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Abstract
Tobacco (Nicotiana tabacum L. cv. Wisconsin 38) cells grown in suspension culture at 26.degree. C produce heat shock proteins (HSP) when exposed to elevated temperature of 34.degree.-42.degree. C. At 34.degree. and 38.degree. C synthesis of normal proteins is maintained, while HSP are expressed within 30 min after initiation of the shock. At 42.degree. C, HSP are still expressed but normal proteins are made at a reduced rate or not at all. Exposure of cells to 38.degree. C allows for a full expression of HSP without inhibition of the synthesis of normal proteins. Induced synthesis of HSP at 38.degree. C is maximal 1-2 h after elevation of temperature and diminishes thereafter through at least 6 h. Cells growing asynchronously in the logarithmic phase of growth produce HSP at a much higher rate than those in the stationary phase. The ability to synthesize HSP disappears about 1 generation time before the cells reach a growth plateau.