Overexpression of MdPIP1;2 affects plant low temperature stress tolerance

Plasma membrane intrinsic proteins (PIPs) are highly efficient water-selective channels that play vital roles in maintaining cellular water balance and improving plant stress tolerance. To elucidate the function of MdPIP1;2 in cold stress response, we generated transgenic Arabidopsis thaliana and apple calli overexpressing MdPIP1;2. Under 4 °C treatment, MdPIP1;2 overexpression significantly promoted seed germination and root elongation in A. thaliana, and enhanced growth of transgenic apple calli compared with wild type. GUS reporter assays demonstrated that the MdPIP1;2 promoter exhibited tissue-specific and cold-inducible expression patterns. Using a yeast one-hybrid assay, the transcription factor MdCBF-l1 was identified as a positive regulator directly binding to the MdPIP1;2 promoter. RNA-seq revealed that MdPIP1;2 regulates stress-related genes associated with antioxidant defense and cold response. Collectively, these results indicate that MdPIP1;2, under the positive regulation of MdCBF-l1, enhances cold tolerance by coordinating transcriptional reprogramming and stress-responsive pathways. This study provides new insights into the molecular mechanisms of PIP-mediated cold adaptation in plants.