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
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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.
KeywordsFlowering time NF-Y CONSTANS FT CCAAT-box
Nuclear Factor Y
Heme Activator Protein
FLOWERING LOCUS T
SUPPRESSOR OF OVEREXPRESSION OF CO 1
We thank Alemu Belachew, Han-Chang Chang and Megan McPartland, for excellent experimental assistance. Hans Holtan for assistance with statistical analysis, and Shiv Tiwari, Neal Gutterson, Rajnish Khanna, Jacqueline Heard, Gabriela Vaduva, Venkatramana Pegadaraju and Michael Luethy for critical discussion and comments on the manuscript.
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