Dlo-miR164a-DlNAC100 module regulates floral bud induction by activating DlCOL4 expression in longan.

Longan (Dimocarpus longan Lour.) is an economically significant subtropical crop of the Sapindaceae family. Floral bud induction is a critical process that directly determines fruit yield and quality in longan cultivation. However, the molecular mechanisms underlying floral bud induction remain largely unclear. Here, through integrating miRNAome, degradome, and transcriptome analyses, we identified 109 known and 320 novel miRNAs along with their 585 targets during longan floral bud induction. The dlo-miR164a-DlNAC100 module was identified as a key regulator during the physiological differentiation stage of floral induction. The ectopic expression of dlo-MIR164a and DlNAC100 in Arabidopsis thaliana delayed and promoted flowering, respectively. Consistently, overexpression of dlo-MIR164a and silencing of its target DlNAC100 in longan apical buds delayed floral bud differentiation, whereas DlNAC100 overexpression accelerated it. Further analyses demonstrated that DlNAC100 acts upstream of CONSTANS-LIKE 4 (DlCOL4), FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (DlFKF1), and GIGANTEA (DlGI), while DlCOL4 directly activates the expression of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (DlSOC1). Similar to DlNAC100, transient expression of DlCOL4 in longan apical buds promoted floral bud differentiation. Our findings revealed a dlo-miR164a-DlNAC100-DlCOL4-DlSOC1 regulatory cascade that orchestrates floral induction through the integration of miRNA-mediated gene silencing with the photoperiod-responsive pathway. This study provides novel insights into the molecular regulatory mechanism of floral bud induction in longan and woody fruit trees.