Abstract
PhyA and phyB share similar structures but perform distinct physiological functions. Properties specific to phyA include; 1) rapid degradation in cR, 2) nuclear accumulation in cFR, 3) physiological responses in cFR (FR-HIR). By contrast, physiological responses in cR are mediated mainly by phyB. In the present study, chimeric phytochromes in which each of four domains of phytochrome (N-terminal extension+PAS (N-PAS), GAF, PHY and C-terminal) were derived from either phyA or phyB. These chimeric phytochromes were fused to GFP and expressed under the control of 35S promoter in the phyA phyB double mutant of Arabidopsis. Confocal microscopic observation of the resulting plants demonstrated that degradation in cR and nuclear accumulation in cFR mainly determined by the structure of N-PAS. For FR-HIR, PHY played an important role in addition to N-PAS. Taken together, phyA and phyB perform their proper functions through complex interactions between different domains.
