The blue light-dependent phosphorylation of the CCE domain determines the photosensitivity of Arabidopsis CRY2

摘要

Arabidopsis cryptochrome 2 (CRY2) is a blue light receptor that mediates light inhibition of hypocotyl elongation and long-day promotion of floral initiation. CRY2 is known to undergo blue light-dependent phosphorylation, which is believed to serve regulatory roles in the function of CRY2. We report here a biochemical and genetics study of CRY2 phosphorylation. Using mass spectrometry analysis, we identified at least three serine residues in the CCE domain of CRY2 (S588, S599, and S605) that undergo blue light-dependent phosphorylation in Arabidopsis seedlings. A study of serine-substitution mutations of the CCE domain of CRY2 demonstrates that CRY2 contains two types of phosphorylation in the CCE domain, one in the serine cluster that cause electrophoretic mobility upshift and the other outside of the serine cluster that do not seem to cause mobility upshift. We showed that mutations in the serine residues within and outside of the serine cluster diminished blue light-dependent CRY2 phosphorylation, degradation, and physiological activities. These results support the hypothesis that blue light-dependent phosphorylation of the CCE domain determines the photosensitivity of Arabidopsis CRY2.