Abstract
Pretreatment of heat shock at a temperature slightly higher than germinating temperature induces various genes and the acquisition of higher temperature tolerance. We found that HSP90 negatively regulates heat-inducible genes and transient inhibition of HSP90 induces heat-inducible genes and heat adaptation in Arabidopsis. Heat shock reduces the activity of an exogenously expressed glucocorticoid receptor, a client of HSP90, in transgenic Arabidopsis. This indicates that heat shock reduced HSP90 activity in vivo. Heat shock or HSP90 inhibitors induce the genes that have heat shock response element (HSE) in its promoter, suggesting that heat shock transcription factor (HSF) is involved in the response. Several HSF genes constitutively express in Arabidopsis, suggesting that HSP90 actively suppresses HSF function and heat shock transiently inactivate HSP90 to activate HSF. Overall, these results indicate that HSP90 regulates heat adaptation in plants and transient HSP90 inhibition is useful to protect plants from unceremoniously occurring heat-induced damage.
