Short-Photoperiod Induces Floral Induction Involving Carbohydrate Metabolism and Regulation by VcCO3 in Greenhouse Blueberry.

Blueberry flower buds cultivated in greenhouses develop during both autumn and spring, with floral induction being a critical process for flowering, influenced by environmental factors. This study aimed to clarify the regulatory mechanisms governing floral induction in greenhouse blueberries, focusing on the similarities and differences in flower bud differentiation between the spring and autumn seasons. Understanding these mechanisms is pivotal for enhancing blueberry production. In this study, we analysed the phenotypic characteristics associated with flower bud differentiation and observed that short photoperiods markedly affect the induction process. Transcriptomic analyses revealed distinct major metabolic pathways activated in autumn compared to spring. Seasonal variations in carbohydrate metabolism were also noted, with sucrose hydrolysis being prominent in autumn and sucrose synthesis prevailing in spring. The interplay between circadian rhythms and photosynthesis appeared to facilitate the allocation of sugars for bud development. Subsequent investigations underscored the sensitivity of VcCO3 to variations in photoperiod. Predominantly localised in the nucleus, VcCO3 facilitated floral induction in response to short photoperiods by activating the expression of downstream genes, including VcFT, VcLFY, VcAP3, and VcSOC1. Furthermore, VcCO3 exhibits a close association with the sugar metabolism gene VcSUS, promoting increased sucrose concentrations.