Genetic studies on continuous flowering in woody plant .

Continuous flowering is a key horticultural trait in ornamental plants, whereas the specific molecular regulation mechanism remains largely unknown. In sweet osmanthus ( Lour.), plants based on their flowering characteristics are divided into once-flowering (OF) habit and continuous flowering (CF) habit. Here, we first described the flowering phenology shifts of OF and CF habits in sweet osmanthus through paraffin section and microscope assay. Phenotypic characterization showed that CF plants had constant new shoot growth, floral transition, and blooming for 1 year, which might lead to a continuous flowering trait. We performed the transcriptome sequencing of OF and CF sweet osmanthus and analyzed the transcriptional activity of flowering-related genes. Among the genes, three floral integrators, , , and , had a differential expression during the floral transition process in OF and CF habits. The expression patterns of the three genes in 1 year were revealed. The results suggested that their accumulations corresponded to the new shoots occurring and the floral transition process. Function studies suggested that acted as a flowering activator, whereas was a flowering inhibitor. Yeast one-hybrid assay indicated that was a common upstream transcription factor of and , suggesting the vital role of in continuous flowering regulation. These results provide a novel insight into the molecular mechanism of continuous flowering.