Auxin biosynthetic key gene CpYUC10B in embryo involved in large-fruited Chinese cherry massive abscission during the pit hardening process.

Chinese cherry [Cerasus pseudocerasus (Lindl.) G.Don] is an economically important Rosaceae fruit crop in China. Massive fruit abscission in the majority of large-fruited Chinese cherry landraces leads to a catastrophic yield loss, hindering the development of the Chinese cherry industry. Herein, we performed systematic physiological analyses to comprehensively characterize the dynamic changes in auxin-centered phytohormones during fruit development across four Chinese cherry landraces exhibiting varying degrees of fruit abscission. These analyses, along with exogenous indole-3-acetic acid (IAA) rescue experiments, confirmed that the endogenous phytohormone imbalance triggered by reduced IAA accumulation in embryos is the core cause of young fruit abscission. Transcriptomic profiling revealed divergent expression patterns of genes associated with IAA synthesis and transport in the embryo, pedicel, and flesh at two critical fruit developmental stages. Weighted gene co-expression network analysis prioritized the rate-limiting YUCCA flavin monooxygenase encoding gene CpYUC10B. Transient overexpression of CpYUC10B elevated IAA levels and upregulated polar auxin transporter gene CpPIN1 expression in embryos, pedicels, and flesh, while repressing the expression of cell wall hydrolase genes in pedicels, consequently reducing fruit abscission. Conversely, VIGS-mediated silencing produced opposite effects. Meanwhile, ectopic overexpression of CpYUC10B in tomato delayed distal pedicel abscission after flower removal, accompanied by elevated IAA levels in the abscission zone, upregulated expression of SlPIN1, and downregulated expression of cell wall hydrolase genes (SlEXLB1, SlBGL12, SlPG, and SlPME7). Collectively, our findings provide a valuable theoretical foundation and practical reference for enhancing yield stability, and offer a new target gene for the genetic improvement of large-fruited cultivars.