Cytological and Transcriptomic Analyses Reveal the Regulatory Mechanisms of Flowering and Petaloid-Anther Development in Camellia oleifera.

Gibberellins (GAs) play important roles in regulating reproductive development, especially flower development. However, the regulation of GA metabolism and GA signaling component genes of flower bud development in Camellia oleifera is not entirely understood. In this study, 6-year-old C. oleifera 'Huashuo' was used as the experimental material. Exogenous GA and GA biosynthesis inhibitors, chlormequat chloride (CCC) and uniconazole (UCZ), were applied to investigate the flower development, levels of GA, GA metabolism, and the expression of genes involved in GA signaling across the different treatments. Our results demonstrate that exogenous GA promoted flower bud growth and accelerated blooming, with the rate of petaloid-anther transformation reaching up to 64.11% during the peak blooming period. Cytological analysis showed that the anthers in the GA-treated flowers exhibited abnormal longitudinal elongation 30 days after spraying, and gradually developed into petaloid anthers. KEGG analysis revealed that the GA treatment regulated the plant hormone signal transduction. The genes encoding DELLA protein accounted for the largest proportion (52.45%) of the gibberellin signal transduction pathway DEGs. GA enhanced gibberellin content by regulating the gibberellin biosynthesis gene CoGA20ox1 during early flower development, and GID1 also showed a significant response to GAs. Additionally, the expression of genes associated with flower development (FT, LFY, SOC1, SVP) and those involved in petaloid-anther (MADS-box family members AP1, AGL8) exhibited significant differences. These results elucidated the regulatory effects of gibberellins and their inhibitors on anther development via the GA pathway in C. oleifera, which provides a foundation for further investigation into the mechanism of flower development.