title: Regulation of Carotenoid Biosynthesis by Shade Relies on Specific Subsets of Antagonistic Transcription Factors and Cofactors.
abstract: Carotenoids are photosynthetic pigments essential for the protection against excess light. During deetiolation, their production is regulated by a dynamic repression-activation module formed by PHYTOCHROME-INTERACTING FACTOR1 (PIF1) and LONG HYPOCOTYL5 (HY5). These transcription factors directly and oppositely control the expression of the gene encoding PHYTOENE SYNTHASE (PSY), the first and main rate-determining enzyme of the carotenoid pathway. Antagonistic modules also regulate the responses of deetiolated plants to vegetation proximity and shade (i.e. to the perception of far-red light-enriched light filtered through or reflected from neighboring plants). These responses, aimed to adapt to eventual shading from plant competitors, include a reduced accumulation of carotenoids. Here, we show that PIF1 and related photolabile PIFs (but not photostable PIF7) promote the shade-triggered decrease in carotenoid accumulation. While HY5 does not appear to be required for this process, other known PIF antagonists were found to modulate the expression of the Arabidopsis (Arabidopsis thaliana) PSY gene and the biosynthesis of carotenoids early after exposure to shade. In particular, PHYTOCHROME-RAPIDLY REGULATED1, a transcriptional cofactor that prevents the binding of true transcription factors to their target promoters, was found to interact with PIF1 and hence directly induce PSY expression. By contrast, a change in the levels of the transcriptional cofactor LONG HYPOCOTYL IN FAR RED1, which also binds to PIF1 and other PIFs to regulate shade-related elongation responses, did not impact PSY expression or carotenoid accumulation. Our data suggest that the fine-regulation of carotenoid biosynthesis in response to shade relies on specific modules of antagonistic transcriptional factors and cofactors.
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain (J.B.-T., G.T.-O., M.O.-A., N.C.-E., J.F.M.-G., M.R.-C.);School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JF, United Kingdom (G.T.-O., K.J.H.); andInstitució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain (J.F.M.-G.).
authors.forename: Jordi
authors.initials: J
authors.lastname: Bou-Torrent
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain (J.B.-T., G.T.-O., M.O.-A., N.C.-E., J.F.M.-G., M.R.-C.);School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JF, United Kingdom (G.T.-O., K.J.H.); andInstitució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain (J.F.M.-G.).
authors.forename: Gabriela
authors.initials: G
authors.lastname: Toledo-Ortiz
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain (J.B.-T., G.T.-O., M.O.-A., N.C.-E., J.F.M.-G., M.R.-C.);School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JF, United Kingdom (G.T.-O., K.J.H.); andInstitució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain (J.F.M.-G.).
authors.forename: Miriam
authors.initials: M
authors.lastname: Ortiz-Alcaide
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain (J.B.-T., G.T.-O., M.O.-A., N.C.-E., J.F.M.-G., M.R.-C.);School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JF, United Kingdom (G.T.-O., K.J.H.); andInstitució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain (J.F.M.-G.).
authors.forename: Nicolas
authors.initials: N
authors.lastname: Cifuentes-Esquivel
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain (J.B.-T., G.T.-O., M.O.-A., N.C.-E., J.F.M.-G., M.R.-C.);School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JF, United Kingdom (G.T.-O., K.J.H.); andInstitució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain (J.F.M.-G.).
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Halliday
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain (J.B.-T., G.T.-O., M.O.-A., N.C.-E., J.F.M.-G., M.R.-C.);School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JF, United Kingdom (G.T.-O., K.J.H.); andInstitució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain (J.F.M.-G.) jaume.martinez@cragenomica.es manuel.rodriguez@cragenomica.es.
authors.forename: Jaime F
authors.identifier: http://orcid.org/0000-0003-1516-0341
authors.initials: JF
authors.lastname: Martinez-García
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, 08193 Barcelona, Spain (J.B.-T., G.T.-O., M.O.-A., N.C.-E., J.F.M.-G., M.R.-C.);School of Biological Sciences, Edinburgh University, Edinburgh EH9 3JF, United Kingdom (G.T.-O., K.J.H.); andInstitució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain (J.F.M.-G.) jaume.martinez@cragenomica.es manuel.rodriguez@cragenomica.es.
authors.forename: Manuel
authors.identifier: http://orcid.org/0000-0002-1280-2305
authors.initials: M
authors.lastname: Rodriguez-Concepcion
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D008027:Light; D011401:Promoter Regions, Genetic; D036226:Seedlings; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; D014157:Transcription Factors; D002338:Carotenoids