Gene networks underlying faster flowering induction in response to far-red light
Light is one of the main signals that regulates flowering. Low red to far-red ratios accelerate flowering in a wide range of species. The central gene pathways controlling flowering time in Arabidopsis, appear to be largely conserved in legumes. However, numerous examples exist 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 RNA-seq 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 With no lysine kinase, a CCT motif related to CONSTANS, a FLOWERING LOCUS T b2 like protein, and their active downstream cascade. The earlier down-regulation of these genes under blue compared to far-red-enriched light may explain their role in floral induction. A second independent approach (qPCR analysis) confirmed our findings. Contrasting responses to light quality related to reproduction and defence mechanisms were also found. These results will contribute to a better understanding of the molecular basis of flowering in response to light quality in long-day plants.