Induction of thermotolerance and mitotic recombination by heat-shock in Ustilago maydiss.

Wild-type cells of Ustilago maydis which have been briefly heated at 42 °C subsequently acquire resistance to the lethal effects of a higher temperature (48 °C). This induced thermotolerance develops over a 2 h period after treatment at 42 °C and is dependent on protein synthesis. It is distinct from the cellular response to DNA-damaging agents, since mutants deficient in this and other repair processes show the same induced thermotolerance as wild-type cells. However, UV-light treatment does induce some resistance to subsequent heat treatment. A single 48 °C heat treatment increases recombination in heteroallelic diploids, but the same treatment of thermotolerant cells does not stimulate recombination. This suggests that heat treatment can damage DNA, but thermotolerant cells are protected from such damage.