Arabidopsis NF–YC7 Interacts with CRY2 and PIF4/5 to Repress Blue Light-Inhibited Hypocotyl Elongation

Abstract

Light is an important environmental factor. Plants adapt to their light environment by developing the optimal phenotypes. Light-mediated hypocotyl growth is an ideal phenotype for studying how plants respond to light. Thus far, many signaling components in light-mediated hypocotyl growth have been reported. Here, we focused on identifying the transcription factors (TFs) involved in blue light-mediated hypocotyl growth. We analyzed the blue-light-mediated hypocotyl lengths of Arabidopsis TF–overexpressing lines and identified three NF–YC proteins, NF–YC7, NF–YC5, and NF–YC8 (NF–YCs being the short name), as the negative regulators in blue light-inhibited hypocotyl elongation. NF–YC–overexpressing lines developed longer hypocotyls than those of the wild type under blue light, while the deficient mutants nf–yc5nf–yc7 and nf–yc7nf–yc8 failed to exhibit hypocotyl elongation under blue light. NF–YCs physically interacted with CRY2 (cryptochrome 2) and PIF4/5 (phytochrome interacting factor 4 or 5), while the NF–YCs–PIF4/5 interactions were repressed by CRY2. Moreover, the overexpression of CRY2 or deficiency of PIF4/5 repressed NF–YC7–induced hypocotyl elongation under blue light. Further investigation revealed that NF–YC7 may increase CRY2 degradation and regulate PIF4/5 activities under blue light. Taken together, this study will provide new insight into the mechanism of how blue light inhibits hypocotyl elongation.