Transcriptomic and physiological analyses reveal the mechanism of acetylene-induced flowering in Guzmania 'Denise'

In Bromeliaceae cultivation, flowering regulation remains a major challenge, and calcium carbide is widely used as a flowering stimulant because of its low cost and ease of application. Upon contact with water, calcium carbide releases acetylene, which subsequently induces flowering in plants. However, to date, no systematic studies have elucidated the mechanisms by which acetylene triggers floral bud differentiation in bromeliads. This study treated the ornamental bromeliad Guzmania 'Denise' with acetylene-saturated water and conducted an integrated analysis combining transcriptomic and physiological approaches. The results showed that the differentially expressed genes were highly enriched in pathways related to cell wall synthesis and remodeling, flavonoid biosynthesis, starch and sucrose metabolism, hormone signal transduction, and multilayer transcriptional regulation. As floral bud differentiation progressed, the contents of starch, soluble sugars, total flavonoids, and ZR in the apical buds increased, whereas those of IAA, ABA, and GAs decreased. AgNO₃ inhibited the acetylene-induced increase in ACC content and blocked the flowering response triggered by acetylene. Mechanistically, acetylene-induced floral bud differentiation is mediated by the upregulation of key enzymes such as ACO, thereby enhancing endogenous ethylene biosynthesis. The hormonal signal is then transduced through ethylene receptors. Hd3a/FT-like genes are highly expressed and transported to the shoot apex, where they activate floral meristem identity genes such as MADS14, thereby initiating the transition from vegetative to reproductive growth in Guzmania 'Denise'. This work enhances the theoretical basis of flowering regulation in Bromeliaceae and facilitates the development of improved flowering control methods.