Analysis of rice ER-resident J-proteins reveals diversity and functional differentiation of the ER-resident Hsp70 system in plants

J Exp Bot. 2013 Dec;64(18):5429-41. doi: 10.1093/jxb/ert312. Epub 2013 Oct 23.


The heat shock protein 70 (Hsp70) chaperone system participates in protein folding and quality control of unfolded proteins. To examine the roles of co-chaperones in the rice Hsp70 chaperone system in the endoplasmic reticulum (ER), the functions of six ER-resident J-proteins (OsP58A, OsP58B, OsERdj2, OsERdj3A, OsERdj3B, and OsERdj7) in rice were investigated. The expression of OsP58B, OsERdj3A, and OsERdj3B was predominantly up-regulated in roots subjected to ER stress. This response was mediated by signalling through ATF6 orthologues such as OsbZIP39 and OsbZIP60, but not through the IRE1/OsbZIP50 pathway. A co-immunoprecipitation assay demonstrated that OsP58A, OsP58B, and OsERdj3B preferentially interact with the major OsBiP, OsBiP1, while OsERdj3A interacts preferentially with OsBiP5, suggesting that there are different affinities between OsBiPs and J-proteins. In the endosperm tissue, OsP58A, OsP58B, and OsERdj2 were mainly localized in the ER, whereas OsERdj2 was localized around the outer surfaces of ER-derived protein bodies (PB-Is). Furthermore, OsERdj3A was not expressed in wild-type seeds but was up-regulated in transgenic seeds accumulating human interleukin-7 (hIL-7). Since ERdj3A-green fluorescent protein (GFP) was also detected in vacuoles of callus cells under ER stress conditions, OsERdj3A is a bona fide vacuole-localized protein. OsP58A, OsP58B and OsERdj3A were differentially accumulated in transgenic plants expressing various recombinant proteins. These results reveal the functional diversity of the rice ER-resident Hsp70 system.

Keywords: BiP; ER stress; Hsp70; J-protein; endoplasmic reticulum; rice..

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum Stress
  • Endosperm / metabolism
  • Gene Expression Regulation, Plant
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / metabolism*
  • Humans
  • Interleukin-17 / genetics
  • Interleukin-17 / metabolism
  • Molecular Sequence Data
  • Oryza / genetics
  • Oryza / metabolism*
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Plant Roots / genetics
  • Plant Roots / metabolism
  • Plants, Genetically Modified / genetics
  • Seeds / genetics
  • Seeds / physiology
  • Up-Regulation


  • HSP70 Heat-Shock Proteins
  • Interleukin-17
  • Plant Proteins
  • Green Fluorescent Proteins