Transcription factor PmNAC90 delays flower induction through IAA regulation in Prunus mume

NAC transcription factors play a pivotal role in plant development and stress responses, but their functional dynamics in flower induction remain unexplored in woody plant species. This study identified a NAC module, PmNAC90-PmNAC32, that controls flower induction in Prunus mume. Comprehensive interaction assays confirmed the direct physical binding between PmNAC90 and PmNAC32. Transcriptional profiling revealed that PmNAC90 had significantly higher expression in late-flowering cultivar 'Qingfeng', and its expression was positively regulated by exogenous IAA treatment. PmNAC90 overexpression in Arabidopsis significantly delayed the flowering time through transcriptional repression of core floral integrators and reduced endogenous IAA levels. Mechanistically, PmNAC90 directly activated transcription of the floral repressor PmTFL1 and auxin glycosyltransferase PmUGT84B. PmNAC32 had antagonistic effects through dual regulatory mechanisms: transcriptional repression of PmNAC90 expression and protein interaction-mediated inhibition of the transactivation activity of PmNAC90 on downstream targets. Our findings reveal a NAC-mediated regulatory switch that integrates protein interaction and hormonal signaling to fine-tune flower induction in perennial woody plants, providing critical insights into the evolutionary diversification of NAC functions in flowering control.