Dehydration of yeast: Changes in the intracellular content of Hsp70family proteins

Yeast is known to experience in natural and industrial conditions cyclesof dehydration-rehydration. Several molecular mechanisms can be triggered inresponse to this and other environmental stressors and to rescue yeast cellsof the cytotoxic effect. Since heat shock proteins constitute one of the mostimportant systems of the response to stress we studied whether the pre-induced major stress protein, Hsp70, can cope with yeast cell drying. Toinduce Hsp70 expression the cells of two yeast species, Saccharomycescerevisiae and Debaryomyces hansenii, were subjected to non-lethal heatshock. It was found that during yeast culture growth Hsp70 accumulationoccurred at the exponential growth phase, and there was no marked change inthe protein level at the stationary phase both in aerobic and anaerobicconditions. Interestingly, dehydration of sensitive to this kind of stressS. cerevisiae grown in anaerobic conditions led to the increase of Hsp70expression; to our knowledge this finding was presented for the first time.Dehydration of yeast taken from the stationary growth phase did not cause theinduction of Hsp70 expression. Irrespective of the inducer, Hsp70 did notrescue yeast cells from dehydration stress damages. This result wellcoincides with data of other groups found that Hsp70 in yeast possesseschaperonic activity, and the latter does not impact to an increase inprotective power of the protein demonstrated in many other organisms.