Plasma membrane-localized Hsp40/DNAJ chaperone protein facilitates OsSUVH7-OsBAG4-OsMYB106 transcriptional complex formation for Os HKT1;5 activation

The salinization of irrigated land affects agricultural productivity.HIGH-AFFINITY POTASSIUM(K+)TRANSPORTER 1;5(OsHKT1;5)-dependent sodium(Na+)transport is a key salt tolerance mechanism during rice growth and development.Using a previously generated high-throughput activation tagging-based T-DNA insertion mutant pool,we isolated a mutant exhibiting salt stress-sensitive phenotype,caused by a reduction in OsHKT1;5transcripts.The salt stress-sensitive phenotype of this mutant results from the loss of function of OsDNAJ15,which encodes plasma membranelocalized heat shock protein 40(Hsp40).osdnaj15loss-of-function mutants show decreased plant height,increased leaf angle,and reduced grain number caused by shorter panicle length and fewer branches.On the other háand,OsDNAJ15-overexpression plants showed salt stress-tolerant phenotypes.Intriguingly,salt stress facilitates the nuclear relocation of OsDNAJ15 so that it can interact with OsBAG4,and OsDNAJ15 and OsBAG4synergistically facilitate the DNA-binding activity of OsMYB106 to positively regulate the expression of OsHKT1;5.Overall,our results reveal a novel function of plasma membrane-localized Hsp40protein in modulating,alongside chaperon regulator OsBAG4,transcriptional regulation under salinity stress tolerance.