Blue light diminishes interaction of PAS/LOV proteins, putative blue light receptors in Arabidopsis thaliana, with their interacting partners.

The light, oxygen, or voltage (LOV) domain that belongs to the Per-ARNT-Sim (PAS) domain superfamily is a blue light sensory module. The Arabidopsis thaliana PAS/LOV PROTEIN (PLP) gene encodes three putative blue light receptor proteins, PLPA, PLPB, and PLPC, because of its mRNA splicing variation. PLPA and PLPB each contain one PAS domain at the N-terminal region and one LOV domain at the C-terminal region, while the LOV domain is truncated in PLPC. RNA gel blot analysis showed that PLP mRNA was markedly expressed after exposure to salt or dehydration stress. Yeast two-hybrid screening led to the isolation of VITAMIN C DEFECTIVE 2 (VTC2), VTC2-LIKE (VTC2L), and BEL1-LIKE HOMEODOMAIN 10 proteins (BLH10A and BLH10B) as PLP-interacting proteins. The molecular interaction of PLPA with VTC2L, BLH10A or BLH10B, and that of PLPB with VTC2L were diminished when yeasts were grown under blue light illumination. Furthermore, the possible binding of flavin chromophore to PLPA and PLPB was demonstrated. These results imply that the LOV domain of PLPA and PLPB functions as a blue light sensor, and suggest the applicability of these interactions to blue light-dependent switching in transcriptional regulation in yeast or other organisms.