The CNT1 Domain of Arabidopsis CRY1 Alone Is Sufficient to Mediate Blue Light Inhibition of Hypocotyl Elongation

Cryptochromes (CRY) are photolyase-like blue light receptors that mediate various light responses in plants and animals. In Arabidopsis, there are two homologous cryptochromes, CRY1 and CRY2, which mainly regulate photomorphogenesis and photoperiodic flowering, respectively (Guo et al., 1998; Lin et al., 1998). Cryptochromes are structurally divided into an N-terminal domain related to the photolyase and a C-terminal extension domain (Yang et al., 2000; Cashmore, 2003). The C-terminal domains of CRY1 and CRY2 (CCT1 [residues 490–681] and CCT2 [residues 486–612], also known as CCE1 and CCE2) are shown to mediate blue light signaling, whereas the N-terminal domains of CRY1 and CRY2 (CNT1 [residues 1–489] and CNT2 [residues 1–485]) are known to bind chromophores to sense blue light and mediate CRY dimerization (Yang et al., 2000; Brautigam et al., 2004; Sang et al., 2005).