Abstract
We have isolated all phytochrome mutants (phyA, phyB and phyC) from rice (Oryza sativa) and have produced all combinations of double mutants. Seedlings of phyB and phyBphyC mutants exhibited a partial loss of sensitivity to continuous red light (Rc) but still showed significant de-etiolation responses. The responses to Rc were completely canceled in phyAphyB double mutants. These results indicate that phyA and phyB act in a highly redundant manner to control de-etiolation under Rc. Under continuous far-red light (FRc), phyA mutants showed partially impaired de-etiolation and phyAphyC double mutants showed no significant residual phytochrome responses, indicating that not only phyA but also phyC is involved in the photoperception of FRc in rice. Interestingly, the phyBphyC double mutant displayed clear R/FR reversibility in the pulse-irradiation experiments, indicating that both phyA and phyB can mediate the low-fluence response for gene expression.
