S ‑glutathionylation of MaWRKY44 orchestrates a MaZFP139‐MaWRKY44‐MaGSTU07 cascade to enhance banana cold tolerance

Chilling injury caused by low temperatures severely reduces the postharvest quality and marketability of banana fruit. Although glutathione S‑transferase (GST)-mediated reactive oxygen species (ROS) scavenging constitutes a core antioxidant defense against cold oxidative stress, the transcriptional and post‑translational mechanisms governing this process remain largely elusive. Here, we discovered that S‑glutathionylation of the WRKY transcription factor MaWRKY44 functions as a previously unknown redox switch that orchestrates a hierarchical transcriptional cascade to enhance cold tolerance. LC‑MS/MS identified Cys45 and Cys199 as conserved S‑glutathionylation sites of MaWRKY44. Biochemical and molecular analyses revealed a biphasic redox switch: Mild ROS triggers reversible glutathionylation to stabilize MaWRKY44 and enhance its DNA‑binding capacity, whereas sustained oxidative stress drives irreversible cysteine over‑oxidation that abolishes its transcriptional function. Mechanistically, we identified a C2H2 zinc finger transcription factor, MaZFP139, as a direct upstream activator of MaWRKY44, which in turn specifically binds to the W‑box motifs of the MaGSTU07 promoter to drive its transcription. Transient gain‑ and loss‑of‑function assays in banana, together with stable heterologous transformation in tomato, demonstrated that the MaZFP139-MaWRKY44-MaGSTU07 cascade positively mitigates cold‑triggered ROS accumulation and peel browning. Collectively, our findings uncover a multilayer transcriptional‑redox module governing fruit cold tolerance, and provide potential molecular targets for improving postharvest cold storage performance in tropical fruits.