Gene networks underlying faster flowering induction in response to far-red light

Light is one of the most important signals that regulate flowering through quality, quantity and duration. The low red to far-red ratio accelerates flowering in a wide range of species. The central gene pathways for controlling flowering time, identified in arabidopsis, appear to be largely conserved in legumes. However, there are numerous examples of gene duplication and loss. The role of CONSTANS-LIKE genes as integrators of the photoperiod response has been questioned in several dicot species including legumes. In this study on subterranean clover, using whole-genome transcriptome profiling and controlled light spectra, we identified 13 differentially expressed genes related to light signalling, meristem identity and flowering promotion. Of these, we pinpointed genes which seem to link photoperiod and far-red light signalling coding for a CCT motif related to CONSTANS and a FLOWERING LOCUS T b2 like protein, and their active downstream cascade. The earlier down-regulation of these genes observed under blue compared to far-red -enriched light may explain their role in floral induction. We also found contrasting responses to light quality related to reproduction and defence mechanisms. These results will contribute to a better understanding of the molecular basis of flowering in response to different light quality in long-day plants.