Combined hormonomic, transcriptomic, and metabolomic analyses reveal the role of programmed cell death in bud abscission of Chinese chestnut (Castanea mollissima BL.)

Introduction: BL.), making it an agronomically important trait; however, the molecular and metabolic regulatory mechanisms underlying this process remain unclear. Methods: This study used 'the abscission bud' cultivar 'Tima Zhenzhu' and 'the non abscission bud' cultivar 'Dabanhong' as materials. By integrating histology, widely targeted metabolomics, transcriptomics, and hormone quantification, we systematically analyzed the dynamic changes that occurred during key stages of bud programmed cell death (PCD). Results: During bud abscission, typical PCD features were observed, including degradation of the cytoskeleton, cell wall shrinkage, and disintegration of vacuoles, nuclei, and other organelles. Hormone dynamics further revealed that the levels of active cytokinins decreased, whereas auxin precursors, ABA, jasmonic acid, and ethylene accumulated markedly, jointly driving the PCD process. At the S25 and S30 stages, 705 and 4,731 differentially expressed genes (DEGs) were identified, along with 241 and 345 differentially accumulated metabolites (DAMs), respectively. These molecules were significantly enriched in pathways such as plant hormone signal transduction, secondary metabolite biosynthesis, sugar metabolism, and lipid metabolism. Based on multi omics data, this study predicts a co regulatory network for bud PCD, illustrating how ordered programmed cell death is achieved through suppression of growth signals, activation of autophagy and antioxidant systems, and reprogramming of secondary metabolic flux. Discussion: These findings not only revealed the intrinsic molecular landscape of bud abscission in 'Tima Zhenzhu', but also provided potential targets and strategic insights for future metabolic engineering or genetic improvement.