Phosphorylation of MdWRKY70L by MdMPK6/02G mediates reactive oxygen synthesis to regulate apple fruit senescence

ABSTRACT Apple (Malus domestica) is a globally significant crop and a vital dietary component worldwide. During ripening, apples exhibit a longitudinal gradient, ripening first at the stalk cavity and extending toward the calyx pit. Over-ripening in the stalk cavity leads to early senescence, characterized by peel browning, which diminishes fruit quality. This study examines the natural senescence process in 6-year-old ‘Ruixue’ apples by screening transcriptome data to uncover senescence-related genes and validate their molecular functions. Our analysis of antioxidant capacity and reactive oxygen species in different peel regions revealed that malondialdehyde, hydrogen peroxide, and superoxide anion levels increased with senescence, especially in the stalk cavity. Transcriptome clustering and enrichment analyses across developmental stages revealed MdWRKY70L , MdSAG101 , and MdZAT12 as key regulators of peel senescence. Further in vitro and in vivo studies demonstrated that MdWRKY70L is phosphorylated at Ser199 by MdMPK6/02G, enhancing its stability and promoting peel senescence. These findings offer insights for developing strategies to delay fruit senescence and improve postharvest quality control.