Plant Hsp90 and its co-chaperones.

ABSTRACT

Molecular chaperones, central to cellular protein homeostasis, are conserved within species. Hsp90 and its cochaperones participate in major cellular functions such as cell growth, response to biotic and abiotic stresses and differentiation, and are critical to the regulation of these functions. Regulation is done through their interacting with client proteins in various cellular compartments under specific conditions. Plant Hsp90 and its co-chaperones resemble their mammalian counterparts in their structure. They were shown to participate in diverse and unique pathways such as defense mechanism against pathogens, regulation of gene expression by regulation of the silencing of RNAs, transport of pre-proteins into chloroplasts and response to heat stress. In many cases, the Hsp90 interaction with the co-chaperone is a prerequisite to interaction with client proteins and regulation of their function. While our understanding of the interaction of plant Hsp90 and its co-chaperones has been greatly enhanced, the large number of isoforms in plants and the diverse molecular pathways specific to plants still leave many open questions about the regulation, specificity, and biophysical characteristics of the complexes formed and their contribution to the cellular homeostasis.