Mechanism of Core Browning in Different Maturity Stages of ‘Yali’ Pears During Slow-Cooling Storage and PbRAV-Mediated Regulation

This study investigated the impact of slow cooling on browning and fruit quality at three maturity stages (early, mid and late). Slow cooling reduced core browning in early/mid-harvest pears, as the browning indexes of early-, middle- and late-harvested 'Yali' pears at 60 d were 0.13, 0 and 0.1, respectively, preserving firmness and soluble solids. Transcriptomic analysis revealed that upregulated genes in 'Yali' pears facilitated stress adaptation via enhanced catalytic activity and phosphorylation. Mid-harvested pears exhibited activation of phosphorus metabolism and DNA repair mechanisms to maintain cellular homeostasis, whereas the late-harvested counterparts showed significant suppression of photosynthesis-related pathways and pyrimidine metabolism, which collectively accelerated senescence progression. Universal downregulation of hormone-response pathways such as ethylene and auxin revealed systemic stress adaptation decline. Then, the PbRAV transcription factors' role was also studied. EMSA confirmed that GST-PbRAV2 binds to the PbLAC15 promoter, linking RAV2 to laccase regulation. Overripe pears showed PbRAV2 dysregulation, impairing LAC15 suppression and accelerating browning. Findings provide a theoretical basis for using slow cooling to mitigate browning in pear storage.