title: High pigment1 mutation negatively regulates phototropic signal transduction in tomato seedlings.
abstract: Phototropins and phytochromes are the major photosensory receptors in plants and they regulate distinct photomorphogenic responses. The molecular mechanisms underlying functional interactions of phototropins and phytochromes remain largely unclear. We show that the tomato (Lycopersicon esculentum) phytochrome A deficient mutant fri lacks phototropic curvature to low fluence blue light, indicating requirement for phytochrome A for expression of phototropic response. The hp1 mutant that exhibits hypersensitive responses to blue light and red light reverses the impairment of second-positive phototropic response in tomato in phytochrome A-deficient background. Physiological analyses indicate that HP1 functions as a negative regulator of phototropic signal transduction pathway, which is removed via action of phytochrome A. The loss of HP1 gene product in frihp1 double mutant allows the unhindered operation of phototropic signal transduction chain, obviating the need for the phytochrome action. Our results also indicate that the role of phytochrome in regulating phototropism is restricted to low fluence blue light only, and at high fluence blue light, the phytochrome A-deficient fri mutant shows the normal phototropic response.
authors.affiliation: School of Life Sciences, University of Hyderabad, Hyderabad-500046, India.
authors.forename: Ankanagari
authors.initials: A
authors.lastname: Srinivas
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Behera
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Kagawa
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Wada
authors.forename: Rameshwar
authors.initials: R
authors.lastname: Sharma
mesh_terms: D002736:Chloroplasts / Q000502:physiology / Q000528:radiation effects; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D008027:Light; D018551:Solanum lycopersicum / Q000235:genetics / Q000254:growth & development* / Q000528:radiation effects; D009154:Mutation; D018524:Phototropism / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D010834:Phytochrome / Q000096:biosynthesis* / Q000528:radiation effects; D051942:Phytochrome A; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D013997:Time Factors
chemical_list: D051942:Phytochrome A; D010940:Plant Proteins; D010834:Phytochrome