Abstract
Pharbitis nil cv. Violet is the absolute short-day (SD) plant, that is used as a model plant to study the physiology of SD flowering response. P. nil cv. Violet 7-day-old seedling can be induced to flower by a single 16-h dark treatment. We had isolated PnCOP1 (P. nil CONSTITUTIVE PHOTOMORPHOGENIC1) using a fluorescent differential display (FDD) method. In Arabidopsis thaliana, COP1 functions to repress flowering and photomorphogenesis. To clarify the role of PnCOP1 in flowering, we made PnCOP1-RNAi transformants. The number of flower buds decreased in PnCOP1-RNAi transformants by a single inductive darkness. That was correlated with decreased expression of PnFT1 (P. nil FLOWERING LOCUS T1, that is the flowering hormone gene). In contrast with A. thaliana's finding, these data suggested that PnCOP1 is a flowering promoter. We also present the pattern of expression of PnCOP1 under various day lengths and effect of light off signal on the phase setting of PnCOP1 expression to discuss photoperiodic flowering pathway in P. nil cv. Violet.
