PsGA2ox1 -mediated gibberellin inactivation regulates hormonal reprogramming and cell wall remodelling during early fruit abscission in the ‘Fengtang’ plum

'Fengtang' plum (Prunus salicina Lindl. cv. 'Fengtang'), a high-sugar cultivar, suffers from severe yield losses due to early physiological fruit drop. We identified 24 days after flowering as the critical abscission period, which is characterized by ovule abortion and abscission zone formation. Hormonal profiling revealed a significant reduction in gibberellin (GA) and jasmonic acid (JA) levels, along with elevated abscisic acid content, in abscised fruits. Integrated transcriptomic and metabolomic analyses highlighted the central role of hormone signalling pathways. Among the differentially expressed genes, PsGA2ox1, encoding a GA-inactivating enzyme, was highly up-regulated in abscised fruits and exhibited strong negative correlations with bioactive GA and JA levels. Functional validation demonstrated that PsGA2ox1 overexpression reduced GA3 levels and induced the expression of key abscission-related genes, whereas its silencing had the opposite effects. Our findings indicate that PsGA2ox1-mediated GA inactivation plays a pivotal role in modulating hormonal balance and transcriptional reprogramming, which involves cell wall remodelling, during early fruit abscission in plum. This study provides molecular insights into a key regulatory node for fruit retention and identifies a potential target for improving fruit set.