Molecular basis of Recurrent blooming

Roses (Genus Rosa) are polycarpic woody plants with different blooming modes. After a juvenile phase, roses bloom in spring (or early in summer). Some roses have the ability to bloom again during the year. These roses are described as recurrent blooming. Among recurrent blooming roses, roses can flower continuously (continuous flowering) or occasionally later in the season (Occasionally re-blooming). The understanding of the molecular bases of recurrent blooming is an important challenge in the control of flowering in polycarpic plants.

            In the team, we have developed a gene-candidate and transcriptomic approach to isolate key genes involved in blooming control in rose. By analysing in detail rose Arabidopsis homologues of floral initiation genes, we showed the importance of GA metabolism in the first blooming in spring (Foucher et al, 2008; Remay et al, 2010). Furthermore recently, we demonstrated that the mutation of a floral repressor, KSN, a homologue of TERMINAL FLOWER1, is responsible of continuous flowering in rose and woodland strawberry (Iwata et al, 2011). The KSN gene expression is regulated by the plant growth regulator, GA. In spring, non recurrent roses do not accumulate KSN transcript. After the first blooming, KSN transcripts are accumulated and block new blooming. Due to the mutation of KSN, continuous flowering roses do not produce the floral repressor and flower continuously.