Functions as a holding molecular chaperone (holdase) which stabilizes unfolding protein intermediates and rapidly releases them in an active form once stress has abated. Functions as a folding molecular chaperone (foldase) that assists the non-covalent folding of proteins in an ATP-dependent manner (PubMed:23827697). Molecular chaperone involved in R gene-mediated disease resistance. Required for full RPS2-mediated resistance through interaction with RAR1. Possesses probably ATPase activity (PubMed:14504384). Homodimer (PubMed:24036116). Interacts with RAR1 (PubMed:14504384, PubMed:17148606). Interacts with OEP61, OEP64 and OM64 (PubMed:24036116). Interacts with POLL (PubMed:26230318). Interacts with HTD1 (PubMed:25358503). Expressed constitutively in roots only. After heat treatment, expressed in most tissues. Levels also increase after heavy metal treatment. Expressed in pollen during pollen development, germination and tube growth. Expressed during embryo development and young seedling growth. By heat shock and infection by avirulent and virulent bacterial pathogens (P.syringae). The TPR repeat-binding motif mediates interaction with TPR repeat-containing proteins. No visible phenotype under normal growth condition. In case of infection, plants are altered in RPS2-mediated disease resistance. Belongs to the heat shock protein 90 family. Extended N-terminus. Extended N-terminus. Extended N-terminus. Extended N-terminus. Extended N-terminus.