Differentially Expressed Genes Related to Flowering Transition between Once- and Continuous-Flowering Roses

Roses are the most important cut flower crops and widely used woody ornamental plants in gardens throughout the world, and they are model plants for studying the continuous-flowering trait of woody plants. To analyze the molecular regulation mechanism of continuous flowering, comparative transcriptome data of once- and continuous-flowering roses in our previous study were used to conduct weighted gene co-expression network analysis (WGCNA) to obtain the candidate genes related to flowering transitions. The expression patterns of candidate genes at different developmental stages between <i>Rosa chinensis</i> “Old Blush” (continuous-flowering cultivar) and <i>R.</i> “Huan Die” (once-flowering cultivar) were investigated, and the relationship of the key gene with the endogenous hormone was analyzed. The results showed that the expression trends of <i>VIN3-LIKE 1</i> (<i>VIL1</i>), <i>FRIGIDA- LIKE 3</i> (<i>FRI3</i>), <i>APETALA 2- LIKE</i> (<i>AP2-like</i>) and <i>CONSTANS-LIKE 2</i> (<i>CO-like 2</i>) genes were significantly different between “Old Blush” and “Huan Die”, and the expression trends of <i>SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1</i> (<i>SOC1</i>) and <i>CO-like 2</i> were consistent in the flowering transition of “Old Blush” under different environments. The changes in cytokinin and gibberellic acid (GA₃) content were different in the two rose cultivars. The overall change trend of the abscisic acid and GA₃ in the flowering transition of “Old Blush” under different environments was consistent. The promoter sequence of <i>CO-like 2</i> contained a P-box element associated with gibberellin response, as well as binding sites for transcription factors. In a word, we found <i>CO-like 2</i> associated with continuous flowering and some factors that may synergistically regulate continuous flowering. The results provided a reference for elucidating the molecular regulatory mechanisms of continuous-flowering traits in roses.