Abstract
Photoperiod dependent flowering is one of several mechanisms used by plants to initiate the developmental transition from vegetative growth to reproductive growth. The NUCLEAR FACTOR Y (NF-Y) transcription factors are heterotrimeric complexes composed of NF-YA and histone-fold domain (HFD) containing NF-YB/NF-YC, that initiate photoperiod-dependent flowering by cooperatively interacting with CONSTANS (CO) to drive the expression of FLOWERING LOCUS T (FT). This involves NF-Y and CO binding at distal CCAAT and proximal “CORE” elements, respectively, in the FT promoter. While this is well established for the HFD subunits, there remains some question over the potential role of NF-YA as either positive or negative regulators of this process. Here we provide strong support, in the form of genetic and biochemical analyses, that NF-YA, in complex with NF-YB/NF-YC proteins, can directly bind the distal CCAAT box in the FT promoter and are positive regulators of flowering in an FT-dependent manner.
Author Summary For plants to have reproductive success, they must time their flowering with the most beneficial biotic and abiotic environmental conditions - after all, reproductive success would likely be low if flowers developed when pollinators were not present or freezing temperatures were on the horizon. Proper timing mechanisms for flowering vary significantly between different species, but can be connected to a variety of environmental cues, including water availability, temperature, and day length. Numerous labs have studied the molecular aspects of these timing mechanisms and discovered that many of these pathways converge on the gene FLOWERING LOCUS T (FT). This means that understanding precisely how this gene is regulated can teach us a lot about many plant species in both natural and agricultural settings. In the current study, we focus on day length as an essential cue for flowering in the plant species Arabidopsis thaliana. We further unravel the complexity of FT regulation by clarifying the roles of NUCLEAR FACTOR Y genes in day length perception.
