Forchlorfenuron (CPPU) suppresses fruitlet abscission in Areca catechu by modulating carbohydrate allocation,...

CPPU treatment increased the supply of carbohydrates in the fruiting branches, and the upregulation of genes related to lignin synthesis improved the tensile strength of the AZ, thereby inhibiting fruitlet abscission in A. catechu. Forchlorfenuron (CPPU) is a synthetic plant growth regulator with cytokinin activity that effectively promotes cell division and expansion, thereby enhancing fruit set rate and improving fruit quality. In this study, CPPU has been verified to effectively suppress fruitlet abscission in A. catechu. The CPPU treatment resulted in a notable increase in the levels of total sugar, starch, sucrose, glucose, and lignin in the abscission zones (AZs) of A. catechu fruitlets. Concurrently, the levels of ACC (1-aminocyclopropane-1-carboxylic acid) and ABA (abscisic acid) significantly decreased, while the levels of ZR (zeatin riboside) and GA₃ (gibberellic acid) significantly increased. Furthermore, totally 1,503 differentially expressed genes (DEGs) between the AZs treated by CPPU and control have been identified through RNA-Seq, including 778 upregulated and 725 downregulated genes. Within the phytohormone signaling pathways, two genes involved in GA₃ signaling transduction, AcCXE and AcGAST, were significantly upregulated, while AcABI, a gene related to ABA signaling, was significantly downregulated. Additionally, genes involved in sucrose and starch metabolism pathways, such as AcSUS4 and AcFRK, and genes associated with lignin biosynthesis, including AcPAL, AcC4H, AcOMT, and AcF5H, were significantly upregulated. These results suggest that CPPU may accelerate the transport of carbohydrates in the leaves and increasing the carbohydrate supply in fruit-bearing branches, and the elevated lignin content improves the tensile strength of the AZ, thereby suppressing fruitlet abscission. These results not only provide preliminary insights into the regulatory mechanisms underlying the suppression of CPPU on fruitlet abscission, but also offer a practical strategy for improving the management of A. catechu industrial.