ZjPDI1, a Novel S-Nitrosylated Protein, Enhances Postharvest Disease Resistance in Jujube Fruit via the NO-Mediated Redox Signaling and ZjERO1 Interaction.

Nitric oxide (NO) improves postharvest jujube resistance, yet the specific molecular targets remain elusive. Here, we identify the endoplasmic reticulum chaperone ZjPDI1 as a functional target of NO-mediated immunity. Exogenous NO restricted lesion expansion by inducing the expression of ZjPDI1, antioxidant, and defense-related genes. Biochemical assays confirmed that ZjPDI1 is specifically S-nitrosylated at Cys123 and Cys126 within its CGHC catalytic motif. Molecular dynamics simulations demonstrated that this modification increases the structural flexibility of ZjPDI1. In vivo transient overexpression of ZjPDI1 enhanced disease resistance, resulting in H2O2 accumulation and the transcriptional activation of downstream defense genes. Yeast two-hybrid and pull-down assays confirmed a physical interaction between ZjPDI1 and ZjERO1, coupling the ER protein folding complex to the defense-associated redox signaling. These findings indicate that S-nitrosylation alters the conformation of ZjPDI1, and its interaction with ZjERO1 likely serves as a mechanistic basis for the H2O2 accumulation to activate postharvest disease resistance.