HSP101: a key component for the acquisition of thermotolerance in plants.

A sudden elevation in temperature triggers a stress response found in all organisms that brings about a global transition in gene expression. Typically, the expression of most genes is either shut down or greatly attenuated, and a specific group of genes, called heat shock (HS) genes, is rapidly induced to high levels (Schlesinger et al., 1982). Proteins encoded by HS genes enable cells to survive the harmful effects of heat by two general strategies: one group of heat shock proteins (HSPs) acts as molecular chaperones that counteract protein denaturation and aggregation, and other HSPs, including ubiquitin and certain proteases, target nonnative proteins for degradation. The HS response is transient in nature, usually peaking 1 to 2 hr after onset, providing protection from acute episodes of thermal stress. Most major classes of HSPs are present in plants and include the small HSPs (ranging in molecular weight from 15 to 28 kD), HSP60, HSP70 (and a constitutively expressed HS cognate protein, HSC70), HSP90, and HSP100 (Vierling, 1991). As is the case in other organisms, refolding of nonnative proteins in plants is thought to occur in complexes (“refolding machines”) containing HSC70/HSP70 and DnaJ homologs (Lee and Vierling, 2000). The robust synthesis of the numerous small HSPs in the HS response differentiates plants from organisms such as Drosophila, in which expression of HSP70 dominates the response. HSPs facilitate growth and survival of plants not only over the course of transient extremes of temperature but also under conditions of severe heat stress HSP101: A Key Component for the Acquisition of Thermotolerance in Plants