A point mutation in Phytochromobilin Synthase alters the circadian clock and photoperiodic flowering of Medicago truncatula

To expand our understanding of genes controlling flowering in legumes, we screened a TILLING population of Medicago truncatula for mutants displaying a late flowering phenotype. Here, we show that one such mutant results from a disruption in the MtP0BS gene, and in addition to delayed flowering and the characteristic photo-morphogenic defects, also shortens the period of circadian rhythms. We also compared these phenotypes with those of mutants for the PHYA and PHYB genes. Our data suggest that the late flowering of the MtP0BS mutant reflects a deficiency of PHYA and a delayed expression of FT genes and is also associated with altered circadian clock properties. These results support the idea that PHYA inputs light information into the circadian clock, which is translated to regulates the expression of MtFTb1/2 to induce precise flowering in long days in Medicago truncatula