phototropin2

Phototropin2 is a blue-light receptor protein in plants; it is a member of the plant phototropin family that also includes phototropin1. It is encoded by the PHOT2 gene and has been studied in Arabidopsis thaliana as a model. Phototropin2 functions as a flavin-based photoreceptor that detects blue light to trigger light-directed responses.

Phototropin2 has two N-terminal LOV domains (A and B) that bind flavin mononucleotide as chromophore and a C-terminal serine/threonine kinase domain. Upon blue light, a covalent flavin-cysteinyl adduct forms in LOV2, causing a conformational change and activation of kinase activity. The receptor autophosphorylates and transduces signals to downstream targets to elicit cellular responses.

Functions of phototropin2 include mediating phototropism toward blue light, directing chloroplast movements (accumulation at low light and avoidance at high light), promoting stomatal opening, and influencing leaf positioning. It often operates alongside phototropin1, but the two receptors contribute differently depending on light intensity and tissue context.

Signaling interactions involve NPH3/RPT1 family adapters and PKS proteins, which link phot2 activation to modulation of auxin transport and growth responses. Phot2 signaling can operate in coordination with phot1, providing a degree of redundancy and specialization within the blue-light signaling network.

Distribution and significance: phototropin2 is widely conserved across green plants. In Arabidopsis and other species, genetic and biochemical studies of PHOT2 have helped define the blue-light signaling pathway and its integration with growth and developmental programs, offering insights relevant to crop light-use efficiency and adaptability.