Transcriptomic Profiling of Buds Unveils Insights into Floral Initiation in Tea-Oil Tree (<i>Camellia oleifera</i> ‘changlin53’)

Flowering is a key agronomic trait that directly influences the yield of the tea-oil tree (<i>Camellia oleifera</i>). Floral initiation, which precedes flower bud differentiation, represents a critical developmental stage affecting the flowering outcomes. However, the molecular mechanisms underlying floral initiation in <i>C. oleifera</i> remain poorly understood. In this study, buds from five key developmental stages of a 12-year-old <i>C. oleifera</i> cultivar ‘changlin53’ were collected as experimental samples. Scanning electron microscopy was employed to identify the stage of floral initiation. UPLC-MS/MS was used to analyze endogenous gibberellin (GA) concentrations, while transcriptomic analysis was performed to reveal the underlying transcriptional regulatory network. Six GA types were detected during floral initiation and petal development. GA₄ was exclusively detected at the sprouting stage (BII), while GA₃ was present in all samples but was significantly lower in BII and the flower bud primordium formation stage (BIII) than in the other samples. A total of 64 differentially expressed genes were concurrently enriched in flower development, reproductive shoot system development, and shoot system development. Weighted gene co-expression network analysis (WGCNA) identified eight specific modules significantly associated with different developmental stages. The magenta module, containing Unigene0084708 (<i>CoFT</i>) and Unigene0037067 (<i>CoLEAFY</i>), emerged as a key regulatory module driving floral initiation. Additionally, <i>GA20OX1</i> and <i>GA2OX8</i> were identified as candidate genes involved in GA-mediated regulation of floral initiation. Based on morphological and transcriptomic analyses, we conclude that floral initiation of <i>C. oleifera</i> is a continuous regulatory process governed by multiple genes, with the <i>FT</i>-<i>LFY</i> module playing a central role in the transition from apical meristem to floral meristem.