Abstract: Protein folding and disaggregation are crucial processes for survival of cells under unfavorable conditions. A network of molecular chaperones supports these processes. Collaborative action of Hsp70 and Hsp100 proteins is an important component of this network. J-proteins/DnaJ members as co-chaperones assist Hsp70. As against 22 DnaJ sequences noted in yeast, rice genome contains 104 J-genes. Rice J-genes were systematically classified into type A (12 sequences), type B (9 sequences), and type C (83 sequences) classes and a scheme of nomenclature of these proteins is proposed. Transcript expression profiles revealed that J-proteins are possibly involved in basal cellular activities, developmental programs, and in stress. Ydj1 is the most abundant J-protein in yeast. Ydj1 deleted yeast cells are nonviable at 37 ?C. Two rice ortholog proteins of yeast Ydj1 protein namely OsDjA4 and OsDjA5 successfully rescued the growth defect in mutant yeast. As Hsp70 and J-proteins work in conjunction, it emerges that rice J-proteins can partner with yeast Hsp70 proteins in functioning. It is thus shown that J-protein machine is highly conserved.