Unfolded protein response activation compensates endoplasmic reticulum-associated degradation deficiency in Arabidopsis

Abiotic stresses often disrupt protein folding and induce endoplasmic reticulum(ER) stress. There is a sophisticated ER quality control(ERQC) system to mitigate the effects of malfunctioning proteins and maintain ER homeostasis. The accumulation of misfolded proteins in the ER activates the unfolded protein response(UPR) to enhance ER protein folding and the degradation of misfolded proteins mediate by ERassociated degradation(ERAD). That ERQC reduces abiotic stress damage has been well studied in mammals and yeast. However, in plants, both ERAD and UPR have been studied separately and found to be critical for plant abiotic stress tolerance. In this study, we discovered thatUPR-associated transcription factors Atb ZIP17, AtbZIP28 and AtbZIP60 responded to tunicamycin(TM) and Na Cl induced ER stress and subsequently enhanced Arabidopsis thaliana abiotic stress tolerance. They regulated the expression level of ER chaperones and the HRD1-complex components. Moreover, overexpression of Atb ZIP17,Atb ZIP28 and Atb ZIP60 could restore stress tolerance via ERAD in the HRD1-complex mutant hrd3a-2, which suggested that UPR and ERAD have an interactive mechanism in Arabidopsis.