Functional dissection of the cytosolic chaperone network in tomato mesophyll protoplasts.

The heat stress response is universal to all organisms. Upon elevated temperatures, heat stress transcription factors (Hsfs) are activated to up-regulate the expression of molecular chaperones to protect cells against heat damages. In higher plants, the phenomenon is unusually complex both at the level of Hsfs and heat stress proteins (Hsps). Over-expression of both Hsfs and Hsps and the use of RNA interference for gene knock-down in a transient system in tomato protoplasts allowed us to dissect the in vivo chaperone functions of essential components of thermotolerance, such as the cytoplasmic sHsp, Hsp70 and Hsp100 chaperone families, and the regulation of their expression. The results point to specific functions of the different components in protection from protein denaturation and in refolding of denatured proteins.