Hop/Sti1 and Hsp90 Are Involved in Maturation and Transport of a PAMP Receptor in Rice Innate Immunity

Abstract

Plants have evolved innate immunity systems to fight pathogen infection. Pathogen-associated molecular patterns (PAMPs) receptors are receptor-like kinases (RLKs) in plants. However, the maturation and transport of PAMP receptors are not well understood. Here, we characterize the Hsp90 co-chaperone Hop/Sti1, a novel OsRac1 interactor. Hop/Sti1 and cytoplasmic Hsp90 bind the rice chitin receptor OsCERK1 in the endoplasmic reticulum (ER). The OsCERK1 complex is then transported to the plasma membrane (PM) via the Sar1-dependent trafficking system. Impairment of Hop/Sti1 and Hsp90 function reduces the efficiency of OsCERK1 transport to the PM. Hop/Sti1a acts in chitin-triggered defense and rice blast resistance. Our results suggest that Hop/Sti1 and Hsp90 may function to link PAMP receptors and Rac/Rop GTPases. The Hop/Sti1a-Hsp90 chaperone complex appears to have a highly conserved role in the maturation and transport of receptors and ion channels in plants and animals.