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Regulation of flowering time by light quality


The transition to flowering in plants is regulated by environmental factors such as temperature and light1. Plants grown under dense canopies or at high density perceive a decrease in the ratio of red to far-red incoming light. This change in light quality serves as a warning of competition, triggering a series of responses known collectively as the ‘shade-avoidance syndrome’. During shade avoidance, stems elongate at the expense of leaf expansion, and flowering is accelerated2,3. Of the five phytochromes—a family of red/far-red light photoreceptors—in Arabidopsis, phytochrome B (phyB) has the most significant role in shade-avoidance responses4,5, but the mechanisms by which phyB regulates flowering in response to altered ratios of red to far-red light are largely unknown. Here we identify PFT1 (PHYTOCHROME AND FLOWERING TIME 1), a nuclear protein that acts in a phyB pathway and induces flowering in response to suboptimal light conditions. PFT1 functions downstream of phyB to regulate the expression of FLOWERING LOCUS T (FT), providing evidence for the existence of a light-quality pathway that regulates flowering time in plants.

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Figure 1: Phenotypes of pft1, phyA and phyB single, double and triple mutants.
Figure 2: Molecular characterization of PFT1.
Figure 3: FT and CO mRNA levels in WT, phyB, pft1 and pft1 phyB mutants.
Figure 4: PFT1 acts in a light-quality pathway upstream of FT.


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We thank the Kasuza Research Institute and the Arabidopsis Stock Center for providing EST clone APZL03h11R and BAC F2J7, respectively; D. Weigel for providing FT- and CO-overexpressing lines, and for useful advice; P. Wigge, S. Mora-Garcia, D. Weigel, J. Nemhauser, M. Yanovsky and J. Casal for comments on the manuscript; L. Barden for figure preparation; and B. Smoot, N. Ga and M. Ledgerwood for technical assistance. This work was supported by a grant from the National Institutes of Health to J.C. (GM52413) and by the Howard Hughes Medical Institute. P.C. was a fellow of the PEW Latin American Fellows Program and Fundación Antorchas.

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Correspondence to Joanne Chory.

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Cerdán, P., Chory, J. Regulation of flowering time by light quality. Nature 423, 881–885 (2003).

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