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The Nuclear Factor Y subunits NF-YB2 and NF-YB3 play additive roles in the promotion of flowering by inductive long-day photoperiods in Arabidopsis

Kumimoto, Roderick W., Adam, Luc, Hymus, Graham J., Repetti, Peter P., Reuber, T. Lynne, Marion, Colleen M., Hempel, Frederick D., Ratcliffe, Oliver J.
Planta 2008 v.228 no.5 pp. 709-723
Arabidopsis, DNA, flowering, gene expression regulation, loci, models, play activities, proteins, yeasts
Accumulating evidence supports a role for members of the plant Nuclear Factor Y (NF-Y) family of CCAAT-box binding transcription factors in the regulation of flowering time. In this study we have used a genetic approach to show that the homologous proteins NF-YB3 and NF-YB2 have comparable activities and play additive roles in the promotion of flowering, specifically under inductive photoperiodic conditions. We demonstrate that NF-YB2 and NF-YB3 are both essential for the normal induction of flowering by long-days and act through regulation of the expression of FLOWERING LOCUS T (FT). Using an ELISA-based in-vitro assay, we provide a novel demonstration that plant NF-YB subunits are capable of directly binding to a CCAAT-box containing region of the FLOWERING LOCUS T promoter as part of an NF-Y trimer in combination with the yeast HAP2 and HAP5 subunits. These results support an emerging model in which NF-Y complexes provide a component of the DNA target specificity for transcriptional regulators such as CONSTANS.