Unraveling the molecular and metabolic mechanisms of 6-benzylaminopurine-mediated dormancy release in Xianheng 01 apple rootstock

Bud dormancy is a key adaptive strategy in perennial plants, enabling them to survive in adverse environmental conditions. However, it generates challenges in crop cultivation, especially in fruit crops like apple, where synchronized bud break is crucial for consistent growth and yield. The synthetic cytokinin 6-benzylaminopurine (6-BA) promotes dormancy release, but its molecular and metabolic mechanisms remain poorly understood. This study investigates dormancy release in Xianheng 01 apple rootstock nursery plants through integrated transcriptomic, metabolomics, and hormonal analyses. Dormant buds were treated with 6-BA, followed by morphological, biochemical, and molecular profiling conducted over 30 days. 6-BA treatment increased plant height and leaf emergence by increasing the level of endogenous hormones such as cytokinins (DHZR/IPA) and decrease in level of abscisic acid (ABA). Transcriptomics analysis identified 7,009 differentially expressed genes (DEGs) in response to 6-BA treatment. The cytokinin-responsive gene A-ARR8 exhibited a distinct expression pattern, remained upregulated at 1, 3 and 6 d post-treatment but downregulated at 11 d. In contrast ABA related genes SnRK2a/b, PP2C and ABF3 were consistently downregulated throughout the treatment period. Metabolomics analysis identified 2,053 metabolites, showing early-phase dominance of phenylpropanoids and flavonoids, followed by a shift towards ABC transporter-mediated nutrient mobilization. Conjoint analysis highlighted coordinated activation of secondary metabolite biosynthesis and cytokinin signaling. These results demonstrate that 6-BA induces dormancy release through cytokinin-ABA antagonism and phased metabolic reprogramming from stress protection to growth promotion. Our findings provide a comprehensive framework for optimizing dormancy management in apple cultivation and highlight 6-BA as an effective agrochemical for enhancing temperate fruit production.

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