title: Interactions within a network of phytochrome, cryptochrome and UV-B phototransduction pathways regulate chalcone synthase gene expression in Arabidopsis leaf tissue.
abstract: The Arabidopsis gene encoding the key flavonoid biosynthesis enzyme chalcone synthase (CHS) is regulated by several environmental and endogenous stimuli. Here we dissect the network of light signalling pathways that control CHS expression in mature leaves using cryptochrome (cry) and phytochrome (phy) deficient mutants. The UV-A/blue light induction of CHS is mediated principally by cry1, but neither cry1 nor cry2 is involved in UV-B induction or in the UV-A and blue light signalling pathways that interact synergistically with the UV-B pathway to enhance CHS expression. Moreover, these synergistic responses do not require phyA or phyB. Phytochrome is a positive regulator of the cry1 inductive pathway, mediating distinct potentiation and coaction effects. A red light pretreatment enhances subsequent cry1-mediated CHS induction. This potentiation is unaltered in phyA and phyB mutants but much reduced in a phyA phyB double mutant, indicating that it requires principally phyA or phyB. In contrast, the cry1-mediated induction of CHS, without pretreatment, is much reduced in phyB but not phyA mutants, indicating coaction between cry1 and phyB. Further experiments with phy-deficient mutants demonstrate that phyB is a negative regulator of the UV-B inductive pathway. We further show that phyB acts upstream of the points of interaction of the UV-A and blue synergism pathways with the UV-B pathway. We propose that phyB functions to balance flux through the cry1 and UV-B signalling pathways.
authors.affiliation: Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: H K
authors.initials: HK
authors.lastname: Wade
authors.forename: T N
authors.initials: TN
authors.lastname: Bibikova
authors.forename: W J
authors.initials: WJ
authors.lastname: Valentine
authors.forename: G I
authors.initials: GI
authors.lastname: Jenkins
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D017956:Photoreceptor Cells, Invertebrate; D010834:Phytochrome / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology*; D018521:Plant Physiological Phenomena; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D018749:RNA, Plant; D043562:Receptors, G-Protein-Coupled; D015398:Signal Transduction; D014466:Ultraviolet Rays / Q000145:classification
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D010940:Plant Proteins; D018749:RNA, Plant; D043562:Receptors, G-Protein-Coupled; C119828:cry protein, Drosophila; D010834:Phytochrome; D000217:Acyltransferases; C020141:flavanone synthetase