Physiological, metabolomic, and transcriptomic insights into the regulatory mechanisms of fruitlet abscission in ‘Kuerle Xiangli’ pear (Pyrus sinkiangensis Yu)

Fruitlet abscission is a complex developmental process that greatly influences yield in ‘Kuerle Xiangli’ pear (Pyrus sinkiangensis Yu). However, its molecular and metabolic mechanisms remain poorly understood. In this study, we employed an integrative approach that combined physiological assays, transcriptomics, and metabolomics to compare abscission zone (AZ) tissues from persistently setting (SF) and abscising (DF) fruitlets at 10 days after pollination. Multi-omics analyses revealed distinct metabolic and transcriptional profiles in abscising fruitlets. We identified four core pathways that cooperatively regulate abscission: (1) ascorbate and aldarate metabolism, in which key genes (e.g., PbGLDH1, PbASOL) were downregulated concurrently with reduced dehydroascorbate levels, thereby disrupting redox homeostasis; (2) phytohormone signaling, characterized by the suppression of auxin, cytokinin, and gibberellin pathways, alongside enhanced signaling of abscisic acid (ABA), ethylene, and salicylic acid (SA) collectively promote abscission; (3) linoleic acid metabolism, marked by accumulation of oxidized lipids (e.g., 9-HPODE, EpOMEs) and downregulation of PbLOXs, indicative of a shift toward non-jasmonate oxylipin production; and (4) carotenoid biosynthesis, where upregulation of genes such as PbNCED1 and PbPSY increased ABA levels, further stimulating abscission. Additionally, our findings revealed disruptions in sugar-energy metabolism, cell wall remodeling, reactive oxygen species homeostasis, as well as the activation of programmed cell death-like processes. Collectively, this study provides a systems-level understanding of fruitlet abscission, elucidating how the intricate cross-talk between metabolic and hormonal pathways orchestrates this process. Our findings offer promising targets for molecular breeding or phytohormonal management strategies aimed at mitigating fruit drop in pear and related species.