Heat Shock Protein Synthesis in Propagules ofFusarium oxysporumf. sp.niveum

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Abstract
Germlings of Fusarium oxysporum f. sp. niveum respond to elevated temperatures by synthesizing a set of heat shock proteins (HSPs) with apparent molecular masses of 95, 83, 80, 74, 70, 35, and 18 kD. Vital fluorescent staining in germlings decreases in intensity after exposure to elevated temperature levels. Reduction in percentage of intensely stained germlings at 35 and 36 C corresponds to appearance of HSPs. HSP synthesis is observed in germlings as early as 10 min after exposure to heat stress and declines gradually after transfer of the germlings to 25 C. Thermotolerance to high temperatures of 43 or 44 C is acquired by preheating germlings at sublethal levels. This was determined by measurement of survival upon dilution plating, by vital fluorescent staining and incorporation of L-[35S]methionine into protein. The protection effect is abolished in the presence of cycloheximide, indicating dependence on protein synthesis.