The Aquaporin MdPIP2;2 Regulates Glomerella Leaf Spot Resistance in Apple

Plant aquaporins (AQPs), the membrane channels that facilitate the transport of small compounds across plasma membranes or organelle membranes, play a crucial role in regulating various physiological and pathological responses. Here, we report that the apple (Malus domestica) AQP MdPIP2;2 transports H₂O₂ and enhances the resistance of apple to Colletotrichum fructicola, which causes Glomerella leaf spot (GLS). In response to C. fructicola, MdPIP2;2 is phosphorylated at serine 117 (S117), leading to the enhanced ability of transporting H₂O₂. Intriguingly, the apoplastic H₂O₂ induced by C. fructicola infection is the factor that triggers phosphorylation of MdPIP2;2 at S117, which enhances its ability to activate pattern-triggered immunity (PTI) and confer resistance to GLS. Potentially, MdPIP2;2 and MdPIP2;2^S117D (the phosphomimetic mutant) can be used in crops to improve their disease resistance.