Abstract
The analysis of a phytochrome deficient mutant revealed that phytochromes repress flowering in rice, a short-day plant by inducing Ghd7, a strong floral repressor, only in the morning under LD. This regulation is required for critical day-length recognition of florigen expression. However, flowering-time phenotypes of single/double phytochrome mutants suggest that each phytochrome can delay flowering by distinct and coordinated molecular actions. To further study the repression of flowering by phytochromes in rice, we examined all single/double phytochrome mutants for gene expression of flowering-time genes.
For example, we examined the role of each phytochrome for Ghd7 induction. Ghd7 was induced in phyA, phyB, phyC, and phyBphyC, but not in phyAphyB, phyAphyC. These suggested that phyA and/or phyBphyC mediate light signals to induce Ghd7 redundantly. In phyB, Ehd1 was highly expressed independent of day-length although the expression of Ghd7 was not changed much. Moreover, in some cases, de-repressed Ehd1 expression patterns were not associated with florigen expression. We here propose a new model to explain possible roles of each phytochrome in photoperiodic flowering of rice.
