Expression Characterization of AtPDI11 and Functional Analysis of AtPDI11 D Domain in Oxidative Protein Folding

The formation and isomerization of disulfide bonds mediated by protein disulfide isomerase (PDI) in the endoplasmic reticulum (ER) is of fundamental importance in eukaryotes. Canonical PDI structure comprises four domains with the order of - - - . In , the PDI-S subgroup contains only one member, AtPDI11, with an - - organization, which has no orthologs in mammals or yeast. However, the expression pattern of AtPDI11 and the functioning mechanism of AtPDI11 domain are currently unclear. In this work, we found that PDI-S is evolutionarily conserved between land plants and algal organisms. is expressed in various tissues and its induction by ER stress is disrupted in and mutants that are null mutants of key components in the unfolded protein response (UPR) signal transduction pathway, suggesting that the induction of by ER stress is mediated by the UPR signaling pathway. Furthermore, enzymatic activity assays and genetic evidence showed that the domain is crucially important for the activities of AtPDI11. Overall, this work will help to further understand the working mechanism of AtPDI11 in catalyzing disulfide formation in plants.