Arabidopsis NPH3:: A NPH1 photoreceptor-interacting protein essential for phototropism

Phototropism of Arabidopsis thaliana seedlings in response to a blue Light source is initiated by nonphototropic hypocotyl 1 (NPH1), a Light-activated serine-threonine protein kinase. Mutations in three Loci [NPH2, root phototropism 2 (RPT2), and NPH3] disrupt early signaling occurring downstream of the NPH1 photoreceptor, The NPH3 gene, now cloned, encodes a NPH1-interacting protein. NPH3 is a member of a large protein family, apparently specific to higher plants, and may function as an adapter or scaffold protein to bring together the enzymatic components of a NPH1-activated phosphorelay.