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Xing Wang Deng - One of the best experts on this subject based on the ideXlab platform.

  • ArAbidopsis Phytochrome A directly tArgets numerous promoters for individuAlized modulAtion of genes in A wide rAnge of pAthwAys
    The Plant Cell, 2014
    Co-Authors: Xing Wang Deng, Fang Chen, Jeanbenoit Charron, Mingqiu Dai, Xiarong Shi
    Abstract:

    ORCID IDs: 0000-0002-2938-1770 (F.C.); 0000-0002-1816-7007 (B.L.) The fAr-red light (FR) photoreceptor Phytochrome A (phyA) contAins no DNA binding domAin but AssociAtes with the CHALCONE SYNTHASE promoter through its chAperone FAR-RED ELONGATED HYPOCOTYL1 And trAnscription fActors. Here, we performed A genome-wide identificAtion of phyA tArgets using A combinAtion of phyA chromAtin immunoprecipitAtion And RNA sequencing methods in ArAbidopsis thAliAnA. Our results indicAte thAt phyA signAling widely Affects gene promoters involved in multiple FR-modulAted Aspects of plAnt growth. Furthermore, we observed An enrichment of hormone- And stressresponsive elements in the phyA direct tArget promoters, indicAting thAt A much broAder thAn expected rAnge of trAnscription fActors is involved in the phyA signAling pAthwAy. To verify our hypothesis thAt phyA regulAtes genes other thAn light-responsive ones through the interAction with corresponding trAnscription fActors, we exAmined the Action of phyA on one of its direct tArget genes, NAC019, which encodes An Abscisic Acid–dependent trAnscription fActor. The phyA signAling cAscAde not only tArgets two G-boxes on the NAC019 promoter for subsequent trAnscriptionAl regulAtion but Also positively coordinAtes with the Abscisic Acid signAling response for root elongAtion inhibition under FR. Our study provides new insight into how plAnts rApidly fine-tune their growth strAtegy upon chAnges in the light environment by escorting photoreceptors to the promoters of hormone- or stress-responsive genes for individuAlized modulAtion.

  • phosphorylAtion of fAr red elongAted hypocotyl1 is A key mechAnism defining signAling dynAmics of Phytochrome A under red And fAr red light in ArAbidopsis
    The Plant Cell, 2012
    Co-Authors: Yunping Shen, Zhenzhen Zhou, Jigang Li, Fang Chen, Liang Chen, Gang Li, Xing Wang Deng
    Abstract:

    Emerging plAnts hAve to AdApt to A high rAtio of fAr-red light (FR)/red light (R) light in the cAnopy before they reAch the R-enriched direct sunlight. Phytochrome A (phyA) is the single dominAnt photoreceptor in young ArAbidopsis thAliAnA seedlings thAt initiAtes photomorphogenesis in response to A FR-enriched environment And trAnsduces increAsing R signAls to eArly responsive genes. To dAte, how phyA differentiAlly trAnsmits FR And R signAls to downstreAm genes remAins obscure. Here, we present A phyA pAthwAy in which FAR-RED ELONGATED HYPOCOTYL1 (FHY1), An essentiAl pArtner of phyA, directly guides phyA to tArget gene promoters And coActivAtes trAnscription. Furthermore, we identified two phosphorylAtion sites on FHY1, Ser-39 And Thr-61, whose phosphorylAtion by phyA under R inhibits phyA signAling At eAch step of its pAthwAy. DeregulAtion of FHY1 phosphorylAtion renders seedlings colorblind to FR And R. FinAlly, we show thAt the weAker phyA response resulting from FHY1 phosphorylAtion ensures the seedling deetiolAtion process in response to A R-enriched light condition. Collectively, our results reveAl FHY1 phosphorylAtion As A key mechAnism for FR/R spectrum-specific responses in plAnts And An essentiAl event for plAnt AdAption to chAnging light conditions in nAture.

  • Phytochrome A mediAtes rApid red light induced phosphorylAtion of ArAbidopsis fAr red elongAted hypocotyl1 in A low fluence response
    The Plant Cell, 2009
    Co-Authors: Haiyang Wang, Yunping Shen, Zhenzhen Zhou, Suhua Feng, Jigang Li, Anna L Tanwilson, Lijia Qu, Xing Wang Deng
    Abstract:

    Phytochrome A (phyA) is the primAry photoreceptor for mediAting the fAr-red high irrAdiAnce response in ArAbidopsis thAliAnA. FAR-RED ELONGATED HYPOCOTYL1 (FHY1) And its homolog FHY1-LIKE (FHL) define two positive regulAtors in the phyA signAling pAthwAy. These two proteins hAve been reported to be essentiAl for light-regulAted phyA nucleAr AccumulAtion through direct physicAl interAction with phyA. Here, we report thAt FHY1 protein is phosphorylAted rApidly After exposure to red light. Subsequent exposure to fAr-red light After the red light pulse reverses FHY1 phosphorylAtion. Such A phenomenon represents A clAssicAl red/fAr-red reversible low fluence response. The phosphorylAtion of FHY1 depends on functioning phyA but not on other Phytochromes And cryptochromes. Furthermore, we demonstrAte thAt FHY1 And FHL directly interAct with phyA by bimoleculAr fluorescence complementAtion And thAt both FHY1 And FHL interAct more stAbly with the Pr form of phyA in ArAbidopsis seedlings by coimmunoprecipitAtion. FinAlly, in vitro kinAse AssAys confirmed thAt A recombinAnt phyA is Able to robustly phosphorylAte FHY1. Together, our results suggest thAt phyA mAy differentiAlly regulAte FHY1 And FHL Activity through direct physicAl interAction And red/fAr-red light reversible phosphorylAtion to fine-tune their degrAdAtion rAtes And resulting light responses.

  • ArAbidopsis cop1 spA1 complex And fhy1 fhy3 AssociAte with distinct phosphorylAted forms of Phytochrome A in bAlAncing light signAling
    Molecular Cell, 2008
    Co-Authors: Yusuke Saijo, Ute Hoecker, Haiyang Wang, Yunping Shen, Vicente Rubio, Zhenzhen Zhou, Danmeng Zhu, Xing Wang Deng
    Abstract:

    Fine tuning of light signAling is cruciAl to plAnt development. Following light-triggered nucleAr trAnslocAtion, the photoreceptor Phytochrome A (phyA) regulAtes gene expression under continuous fAr-red light And is rApidly destAbilized upon red light irrAdiAtion by E3 ubiquitin ligAses, including COP1. Here we provide evidence thAt the light signAling repressors SPA proteins contribute to COP1-mediAted phyA degrAdAtion And thAt A COP1/SPA1 protein complex is tightly AssociAted with phyA ubiquitinAtion Activity. Furthermore, A phosphorylAted phyA form AccumulAtes in the nucleus And preferentiAlly AssociAtes with the COP1/SPA1 complex. In contrAst, underphosphorylAted phyA predominAntly AssociAtes with the phyA-signAling intermediAtes FHY3 And FHY1. However, COP1 AssociAtes with underphosphorylAted phyA in the Absence of FHY3 or FHY1, suggesting thAt phyA AssociAtions with FHY3 And FHY1 protect underphosphorylAted phyA from being recognized by the COP1/SPA complex. We propose thAt light-induced phyA phosphorylAtion Acts As A switch controlling differentiAl interActions of the photoreceptor with signAl propAgAtion or AttenuAtion mAchineries.

  • the cop1 spA1 interAction defines A criticAl step in Phytochrome A mediAted regulAtion of hy5 Activity
    Genes & Development, 2003
    Co-Authors: Yusuke Saijo, Ute Hoecker, Haiyang Wang, James A Sullivan, Jianping Yang, Yunping Shen, Vicente Rubio, Xing Wang Deng
    Abstract:

    ArAbidopsis COP1 is A constitutive repressor of photomorphogenesis thAt interActs with photomorphogenesis-promoting fActors such As HY5 to promote their proteAsome-mediAted degrAdAtion. SPA1 is A repressor of Phytochrome A-mediAted responses to fAr-red light. Here we report thAt COP1 Acts As pArt of A lArge protein complex And interActs with SPA1 in A light-dependent mAnner. We further demonstrAte the E3 ubiquitin ligAse Activity of COP1 on HY5 in vitro And the AlterAtion of thAt Activity by SPA1. Thus, the COP1-SPA1 interAction defines A criticAl step in coordinAting COP1-mediAted ubiquitinAtion And subsequent degrAdAtion of HY5 with PHYA signAling.

Peter H Quail - One of the best experts on this subject based on the ideXlab platform.

  • Phytochrome-Deficient hy 1 And hy2 Long Hypocotyl MutAnts of ArAbidopsis Are Defective in Phytochrome
    2015
    Co-Authors: Chromophore Biosynt Hesis, Brian M Parks, Peter H Quail
    Abstract:

    The h y l And hy2 long hypocotyl mutAnts of ArAbidopsis contAin normAl levels of immunochemicAlly detectAble Phytochrome A, but the molecule is photochemicAlly nonfunctionAl. We hAve investigAted the biochemicAl bAsis for this lAck of function. When the h y l And hy2 mutAnts were grown in white light on A medium contAining biliverdin IXA, A direct precursor to phytochromobilin, the Phytochrome chromophore, the seedlings developed with A morphologicAl phenotype indistinguishAble from the light-grown wild-type control. RestorAtion of A light-grown phenotype in the h y l mutAnt wAs Also Accomplished by using phycocyAnobilin, A tetrApyrrole AnAlog of phytochro-mobilin. Spectrophotometric And immunochemicAl AnAlyses of the rescued h y l And hy2 mutAnts demonstrAted thAt they possessed wild-type levels of photochemicAlly functionAl Phytochrome thAt displAyed light-induced confor-mAtionAl chAnges in the holoprotein indistinguishAble from the wild type. Moreover, Phytochrome A levels declined in vivo in response to white light in rescued h y l And hy2 seedlings, indicAtive of biliverdin-dependent formAtion of photochemicAlly functionAl Phytochrome A thAt wAs then subject to normAl selective turnover in the fAr-red-light-Absorbing form. Combined, these dAtA suggest thAt the h y l And hy2 mutAnts Are inhibited in chromophore biosynthesis At steps prior to the formAtion of biliverdin IXA, thus potentiAlly cAusing A globAl functionAl deficiency in All members of the Phytochrome photoreceptor fAmily

  • identificAtion of promoter motifs involved in the network of Phytochrome A regulAted gene expression by combined AnAlysis of genomic sequence And microArrAy dAtA
    Plant Physiology, 2003
    Co-Authors: Matthew E Hudson, Peter H Quail
    Abstract:

    SeverAl hundred ArAbidopsis genes, trAnscriptionAlly regulAted by Phytochrome A (phyA), were previously identified using An oligonucleotide microArrAy. We hAve now identified, in silico, conserved sequence motifs in the promoters of these genes by compAring the promoter sequences to those of All the genes present on the microArrAy from which they were sAmpled. This wAs done using A Perl script (cAlled Sift) thAt identifies over-represented motifs using An enumerAtive ApproAch. The utility of Sift wAs verified by AnAlysis of circAdiAn-regulAted promoters known to contAin A biologicAlly significAnt motif. SeverAl elements were then identified in phyA-responsive promoters by their over-representAtion. Five previously undescribed motifs were detected in the promoters of phyA-induced genes. Four novel motifs were found in phyA-repressed promoters, plus A motif thAt strongly resembles the DE1 element. The G-box, CACGTG, wAs A prominent hit in both induced And repressed phyA-responsive promoters. Intriguingly, two distinct flAnking consensus sequences were observed AdjAcent to the G-box core sequence: one predominAting in phyA-induced promoters, the other in phyA-repressed promoters. Such different conserved flAnking nucleotides Around the core motif in these two sets of promoters mAy indicAte thAt different members of the sAme fAmily of DNA-binding proteins mediAte phyA induction And repression. An increAsed AbundAnce of G-box sequences wAs observed in the most rApidly phyA-responsive genes And in the promoters of phyA-regulAted trAnscription fActors, indicAting thAt G-box-binding trAnscription fActors Are upstreAm components in A trAnscriptionAl cAscAde thAt mediAtes phyA-regulAted development.

  • the fhy3 And fAr1 genes encode trAnsposAse relAted proteins involved in regulAtion of gene expression by the Phytochrome A signAling pAthwAy
    Plant Journal, 2003
    Co-Authors: Matthew E Hudson, Peter H Quail, Damon Lisch
    Abstract:

    SummAry The ArAbidopsis mutAnts fAr1 And fhy3 displAy A phenotype of reduced inhibition of hypocotyl elongAtion, which is specific to fAr-red light And therefore specific to the Phytochrome A (phyA)-signAling pAthwAy. We report thAt the proteins encoded by the FAR1 And FHY3 genes Are both relAted to the trAnsposAses of type II MuDR fAmily trAnsposons. We demonstrAte thAt the FAR1 protein is cApAble of ActivAting trAnscription in ArAbidopsis, indicAting thAt it mAy define A type of trAnscriptionAl regulAtor. Using microArrAy expression AnAlysis, we show thAt of 293 mRNAs twofold induced in wild-type Col-0 plAnts by continuous fAr-red light, 85% show reduced responsiveness in the fhy3 mutAnt. NotAble AlterAtions were observed in the responses of genes encoding certAin trAnscription fActors, proteins involved in cell wAll extension, And proteins relAted to redox bAlAnce control. We Also found genes, including some involved in trAnscriptionAl control, which showed Altered trAnscriptionAl behAvior in the dArk-grown mutAnt plAnts. TAken together, our dAtA suggest thAt FAR1 And FHY3 mAy function 'permissively' outside the signAl trAnsduction pAthwAy of light- regulAted development, yet be required for the expression of trAnscriptionAl regulAtory components. An AlternAtive possibility is thAt their role includes both light-signAl trAnsduction And trAnscriptionAl regulAtion of other genes not responsive to light. We propose thAt FAR1 And FHY3 control the expression of their tArget genes by A mechAnism thAt hAs evolved directly from the wAy thAt An AncestrAl, MuDRA-like trAns- posAse bound to the TIRs of mobile elements.

  • the Phytochrome A specific signAling intermediAte spA1 interActs directly with cop1 A constitutive repressor of light signAling inArAbidopsis
    Journal of Biological Chemistry, 2001
    Co-Authors: Ute Hoecker, Peter H Quail
    Abstract:

    SPA1 is A Phytochrome A (phyA)-specific signAling intermediAte thAt Acts As A light-dependent repressor of photomorphogenesis in ArAbidopsis seedlings. It contAins A WD-repeAt domAin thAt shows high sequence similArity to the WD-repeAt region of the constitutive repressor of light signAling, COP1. Here, using yeAst two-hybrid And in vitro interAction AssAys, we show thAt SPA1 strongly And selectively binds to COP1. DomAin mApping studies indicAte thAt the putAtive coiled-coil domAin of SPA1 is necessAry And sufficient for binding to COP1. Conversely, similAr deletion AnAlyses of the COP1 protein suggest thAt SPA1 interActs with the presumed coiled-coil domAin of COP1. To further investigAte SPA1 function in the phyA signAling pAthwAy, we tested whether SPA1, like COP1, mediAtes chAnges in gene expression in response to light. We show thAt spA1 mutAtions increAse the photoresponsiveness of certAin light-regulAted genes within 2 h of light treAtment. TAken together, the results suggest thAt SPA1 mAy function to link the Phytochrome A-specific brAnch of the light signAling pAthwAy to COP1. Hence, our dAtA provide moleculAr support for the hypothesis thAt COP1 is A convergence point for upstreAm signAling pAthwAys dedicAted to individuAl photoreceptors.

  • multiple trAnscription fActor genes Are eArly tArgets of Phytochrome A signAling
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: James M Tepperman, Hursong Chang, Xun Wang, Peter H Quail
    Abstract:

    The Phytochrome fAmily of sensory photoreceptors directs AdAptAtionAl chAnges in gene expression in response to environmentAl light signAls. Using oligonucleotide microArrAys to meAsure expression profiles in wild-type And Phytochrome A (phyA) null-mutAnt ArAbidopsis seedlings, we hAve shown thAt 10% of the genes represented on the ArrAy Are regulAted by phyA in response to A continuous fAr-red light signAl. Strikingly, 44% of the genes responding to the signAl within 1 h Are predicted to encode multiple clAsses of trAnscriptionAl regulAtors. Together with previous dAtA, this observAtion suggests thAt phyA mAy regulAte seedling photomorphogenesis by direct tArgeting of light signAls to the promoters of genes encoding A mAster set of diverse trAnscriptionAl regulAtors, responsible in turn for orchestrAting the expression of multiple downstreAm tArget genes in vArious brAnches of A phyA-regulAted trAnscriptionAl network.

Pillsoon Song - One of the best experts on this subject based on the ideXlab platform.

  • hfr1 A Phytochrome A signAlling component Acts in A sepArAte pAthwAy from hy5 downstreAm of cop1 in ArAbidopsis thAliAnA
    Plant Journal, 2002
    Co-Authors: Youngmi Kim, Pillsoon Song, Jechang Woo, Moonsoo Soh
    Abstract:

    SummAry HFR1, A bAsic helix–loop–helix protein, is known to be required for A subset of Phytochrome A (phyA)-dependent photoresponses. To investigAte the role of HFR1 in light signAlling, we hAve exAmined the genetic interAction between HFR1 And HY5, A positive regulAtor of light signAlling, And COP1, A repressor of photomorphogenesis. Double mutAnt AnAlysis suggests thAt HFR1 mediAtes phyA-dependent inhibition of hypocotyl elongAtion independently of HY5. HFR1 wAs shown to be necessAry for A subset of cop1-triggered photomorphogenic phenotypes in the dArk, including inhibition of hypocotyl elongAtion, grAvitropic hypocotyl growth, And expression of the light-inducible genes CAB And RBCS. Phenotypic AnAlysis of the triple mutAnt cop1hy5hfr1 indicAted thAt both HFR1 And HY5 Are required for cop1-mediAted photomorphogenic seedling development in dArkness, consistent with their Additive roles in phyA-dependent signAlling. TAken together, these results suggest thAt HFR1 might Act downstreAm of COP1, in A sepArAte pAthwAy from HY5, to mediAte photomorphogenesis in ArAbidopsis.

  • rep1 A bAsic helix loop helix protein is required for A brAnch pAthwAy of Phytochrome A signAling in ArAbidopsis
    The Plant Cell, 2000
    Co-Authors: Moonsoo Soh, Youngmi Kim, Sangjo Han, Pillsoon Song
    Abstract:

    Phytochromes Are primAry photoreceptors mediAting diverse responses rAnging from induction of germinAtion to florAl induction in higher plAnts. We hAve isolAted novel recessive rep1 (reduced Phytochrome signAling 1) mutAnts, which exhibit A long-hypocotyl phenotype only under fAr-red light but not under red light. PhysiologicAl chArActerizAtion showed thAt rep1 mutAtions greAtly reduced A subset of Phytochrome A–regulAted responses, including the inhibition of hypocotyl elongAtion, cotyledon expAnsion, modulAtion of grAvitropic growth of hypocotyl, And induction of the CAB (encoding chlorophyll A/b binding protein) gene, without Affecting the AccumulAtion of AnthocyAnin, fAr-red-preconditioned blocking of greening, induction of germinAtion, And induction of CHS (encoding chAlcone synthAse) And FNR (encoding ferredoxin-NADP+ oxidoreductAse) genes. These results suggest thAt REP1 is A positive signAling component, functioning in A brAnch of the Phytochrome A signAling pAthwAy. MoleculAr cloning And chArActerizAtion of the REP1 gene reveAled thAt it encodes A light-inducible, putAtive trAnscription fActor contAining the bAsic helix-loop-helix motif.

Garry C. Whitelam - One of the best experts on this subject based on the ideXlab platform.

  • roles of different Phytochromes in ArAbidopsis photomorphogenesis
    Plant Cell and Environment, 1997
    Co-Authors: Garry C. Whitelam, Paul F Devlin
    Abstract:

    The red/fAr-red light-Absorbing Phytochromes plAy fundAmentAl roles in photoperception of the light environment And the subsequent AdAptAtion of plAnt growth And development. Higher plAnts possess multiple, discrete Phytochromes, the Apoproteins of which Are the products of A fAmily of divergent (PHY) genes. ArAbidopsis thAliAnA hAs At leAst five PHY genes, encoding the Apoproteins of Phytochromes A-E. Through the AnAlysis of mutAnts thAt Are deficient in Phytochrome A or B And the corresponding double mutAnt, it is becoming cleAr thAt these Phytochromes perform both discrete And overlApping roles throughout plAnt development. Through AnAlysis of the phyA phyB double mutAnt, it hAs been possible to define severAl responses thAt Are mediAted by other members of the Phytochrome fAmily. This Article reviews some of the recent progress in the study of Phytochrome-deficient mutAnts of the model plAnt ArAbidopsis thAliAnA.

  • Both Phytochrome A And Phytochrome B Are required for the normAl expression of phototropism in ArAbidopsis thAliAnA seedlings
    Physiologia Plantarum, 1997
    Co-Authors: Abdul-kader Janoudi, Garry C. Whitelam, Radomir Konjević, William Gordon, Kenneth L. Poff
    Abstract:

    The role of Phytochrome A (phyA) And Phytochrome B (phyB) in phototropism wAs investigAted by using the Phytochrome-deficient mutAnts phyA-101, phyB-1 And A phyA/phyB double mutAnt. The red-light-induced enhAncement of phototropism, which is normAlly observed in wild-type seedlings, could not be detected in the phyA/phyB mutAnt At fluences of red light between 0.1 And 19 000 μmol m -2 . The loss of phyB hAs been shown to hAve no AppArent effect on enhAncement, while the loss of phyA resulted in A loss of enhAncement only in the low fluence rAnge (JAnoudi et Al. 1997). The conclusions of the Aforementioned study cAn now be modified bAsed on the current results which indicAte thAt phototropic enhAncement in the high fluence rAnge is mediAted by either phyA or phyB, And thAt other Phytochromes hAve no role in enhAncement. First positive phototropism wAs unAffected in phyA-101 And phyB-1. However, the mAgnitude of first positive phototropism in the phyA/phyB mutAnt wAs significAntly lower thAn thAt of the wild-type LAndsberg pArent. Thus, the presence of either phyA or phyB is required for normAl expression of first positive phototropism. The time threshold for second positive phototropism is unAltered in the phyA-101 And phyB-1 mutAnts. However, the time threshold in the phyA/phyB mutAnt is About 2 h, ApproximAtely six times thAt of the wild type. FinAlly, the mAgnitude of second positive phototropism in both phyA-101 And phyB-1 is diminished in compArison with the wild-type response. Thus, phyA And phyB, Acting independently or in combinAtion, regulAte the mAgnitude of phototropic curvAture And the time threshold for second positive phototropism. We conclude thAt the presence of phyA And phyB is required, but not sufficient, for the expression of normAl phototropism.

  • fAr red light blocks greening of ArAbidopsis seedlings viA A Phytochrome A mediAted chAnge in plAstid development
    The Plant Cell, 1996
    Co-Authors: Simon A. Barnes, Ronaldo Bento Quaggio, Naoko K Nishizawa, Garry C. Whitelam, Nam-hai Chua
    Abstract:

    We hAve chArActerized A fAr-red-light response thAt induces A novel pAthwAy for plAstid development in ArAbidopsis seedlings. This response results in the inAbility of cotyledons to green upon subsequent white light illuminAtion, And the response is suppressed by exogenous sucrose. Studies with mutAnts showed thAt this fAr-red block of greening is Phytochrome A dependent And requires An intAct downstreAm signAling pAthwAy in which FHY1 And FHY3 mAy be components but in which HY5 is not. This highlights A previously undefined brAnchpoint in the Phytochrome signAling pAthwAy. UltrAstructurAl AnAlysis showed thAt the fAr-red block correlAtes with both the fAilure of plAstids to AccumulAte prolAmellAr bodies And the formAtion of vesicles in the stromA. We present evidence thAt the fAr-red block of greening is the result of severe repression of protochlorophyllide reductAse (POR) genes by fAr-red light coupled with irreversible plAstid dAmAge. This results in the temporAl sepArAtion of Phytochrome-mediAted POR; repression from light-dependent protochlorophyllide reduction, two processes thAt normAlly occur in coordinAtion in white light.

  • Phytochrome A Phytochrome b And hy4 Are involved in hypocotyl growth responses to nAturAl rAdiAtion in ArAbidopsis weAk de etiolAtion of the phyA mutAnt under dense cAnopies
    Plant Cell and Environment, 1995
    Co-Authors: Marcelo J Yanovsky, Jorge J Casal, Garry C. Whitelam
    Abstract:

    The roles of Phytochrome A (phyA), Phytochrome B (phyB) And A putAtive blue-light (BL) photoreceptor (HY4) in the control of hypocotyl growth by nAturAl rAdiAtion were investigAted using phyA, phyB And hy4 mutAnts of ArAbidopsis thAliAnA. Full sunlight inhibited hypocotyl growth to A lArger extent in wild-type (WT) thAn in phyA, phyB And, pArticulArly, hy4 seedlings. In WT seedlings, hypocotyl growth wAs promoted by selectively lowering BL irrAdiAnce, lowering red-light (R) plus fAr-red-light (FR) irrAdiAnce or lowering the R/FR rAtio (which wAs Achieved either by increAsing FR or by reducing R). The effects of lowering BL were reduced in hy4 And exAggerAted in phyA seedlings. The effects of lowering R+FR were reduced in phyA And exAggerAted in hy4 seedlings. Neither phyB nor hy4 mutAnts responded to low R/FR rAtios. Neighbouring plAnts reflecting FR without shAding cAused subtle reductions of the R/FR rAtio. This signAl promoted hypocotyl growth in WT but not in phyA, phyB or hy4 seedlings. IntermediAte cAnopy shAde produced similAr effects in All genotypes. Under deep shAde, de-etiolAtion wAs severely impAired in phyA seedlings, which died premAturely. Thus, the FR ‘high-irrAdiAnce reAction’ mediAted by phyA could be importAnt for seedling survivAl under dense cAnopies.

  • photoresponses of light grown phyA mutAnts of ArAbidopsis Phytochrome A is required for the perception of dAylength extensions
    Plant Physiology, 1994
    Co-Authors: Emma Johnson, Nicholas P Harberd, M Bradley, Garry C. Whitelam
    Abstract:

    SeverAl Aspects of the photophysiology of wild-type ArAbidopsis thAliAnA seedlings were compAred with those of A Phytochrome A null mutAnt, phyA-1, And A mutAnt, fhy1, thAt is putAtively involved in the trAnsduction of light signAls from Phytochrome A. Although phyA seedlings displAy A neAr wild-type phenotype when grown in white light (W), they nevertheless displAy severAl photomorphogenic AbnormAlities. Thus, whereAs the germinAtion of wild-type And fhy1 seeds is Almost fully promoted by A pulse of red light (R) or by continuous fAr-red light (FR), phyA seed germinAtion is responsive only to R. Following growth under dAy/night cycles, but not under continuous W, the hypocotyls of light-grown phyA And fhy1 seedlings Are more elongAted thAn those of wild-type seedlings. For seedlings grown under low red/fAr-red (R/FR) rAtio light conditions, phyA And fhy1 seedlings displAy A more mArked promotion of hypocotyl elongAtion thAn wild-type seedlings. SimilArly, seedlings thAt Are doubly null for Phytochrome A And Phytochrome B(phyA phyB) Also hAve more elongAted hypocotyls under low R/FR rAtio conditions thAn phyB seedlings. This indicAtes thAt Phytochrome A Action in light-grown seedlings is AntAgonistic to the Action of Phytochrome B. Although wild-type, fhy1, And phyA seedlings flower At essentiAlly the sAme time under both short-dAy And long-dAy conditions, An obvious consequence of Phytochrome A deficiency is A pronounced lAte flowering under conditions where A short dAy of 8 h of fluorescent W is extended by 8 h of low-fluence-rAte incAndescent light. The evidence thus indicAtes thAt Phytochrome A plAys A role in seed germinAtion, in the control of elongAtion growth of light-grown seedlings, And in the perception of dAylength.

Masaki Furuya - One of the best experts on this subject based on the ideXlab platform.

  • structurAl requirement of bilin chromophore for the photosensory specificity of Phytochromes A And b
    Proceedings of the National Academy of Sciences of the United States of America, 2002
    Co-Authors: Hiroko Hanzawa, Tomoko Shinomura, Katsuhiko Inomata, Takashi Kakiuchi, Hideki Kinoshita, Keishiro Wada, Masaki Furuya
    Abstract:

    Phytochromes Are An importAnt clAss of chromoproteins thAt regulAte mAny cellulAr And developmentAl responses to light in plAnts. The model plAnt species ArAbidopsis thAliAnA possesses five Phytochromes, which mediAte distinct And overlApping responses to light. PhotobiologicAl AnAlyses hAve estAblished thAt, under continuous irrAdiAtion, Phytochrome A is primArily responsible for plAnt's sensitivity to fAr-red light, whereAs the other Phytochromes respond mAinly to red light. The present study reports thAt the fAr-red light sensitivity of Phytochrome A depends on the structure of the lineAr tetrApyrrole (bilin) prosthetic group. By reconstitution of holoPhytochrome in vivo through feeding vArious synthetic bilins to chromophore-deficient mutAnts of ArAbidopsis, the requirement for A double bond on the bilin D-ring for rescuing Phytochrome A function hAs been estAblished. In contrAst, we show thAt Phytochrome B function cAn be rescued with vArious bilin AnAlogs with sAturAted D-ring substituents.

  • isolAtion And chArActerizAtion of rice Phytochrome A mutAnts
    The Plant Cell, 2001
    Co-Authors: Makoto Takano, Tomoko Shinomura, Hiromi Kanegae, Akio Miyao, Hirohiko Hirochika, Masaki Furuya
    Abstract:

    To elucidAte Phytochrome A (phyA) function in rice, we screened A lArge populAtion of retrotrAnsposon (Tos17) insertionAl mutAnts by polymerAse chAin reAction And isolAted three independent phyA mutAnt lines. Sequencing of the Tos17 insertion sites confirmed thAt the Tos17s interrupted exons of PHYA genes in these mutAnt lines. Moreover, the phyA polypeptides were not immunochemicAlly detectAble in these phyA mutAnts. The seedlings of phyA mutAnts grown in continuous fAr-red light showed essentiAlly the sAme phenotype As dArk-grown seedlings, indicAting the insensitivity of phyA mutAnts to fAr-red light. The etiolAted seedlings of phyA mutAnts Also were insensitive to A pulse of fAr-red light or very low fluence red light. In contrAst, phyA mutAnts were morphologicAlly indistinguishAble from wild type under continuous red light. Therefore, rice phyA controls photomorphogenesis in two distinct modes of photoperception—fAr-red light–dependent high irrAdiAnce response And very low fluence response—And such function seems to be unique And restricted to the deetiolAtion process. Interestingly, continuous fAr-red light induced the expression of CAB And RBCS genes in rice phyA seedlings, suggesting the existence of A photoreceptor(s) other thAn phyA thAt cAn perceive continuous fAr-red light in the etiolAted seedlings.

  • elementAry processes of photoperception by Phytochrome A for high irrAdiAnce response of hypocotyl elongAtion in ArAbidopsis
    Plant Physiology, 2000
    Co-Authors: Tomoko Shinomura, Kenko Uchida, Masaki Furuya
    Abstract:

    ElementAry processes of photoperception by Phytochrome A (PhyA) for the high-irrAdiAnce response (HIR) of hypocotyl elongAtion in ArAbidopsis were exAmined using A newly designed irrAdiAtor with LED. The effect of continuous irrAdiAtion with fAr-red (FR) light could be replAced by intermittent irrAdiAtion with FR light pulses if given At intervAls of 3 min or less for 24 h. In this response, the Bunsen-Roscoe lAw of reciprocity held in eAch FR light pulse. Therefore, we determined the Action spectrum for the response by intermittent irrAdiAtion using phyB And phyAphyB double mutAnts. The resultAnt Action spectrum correlAted well with the Absorption spectrum of PhyA in fAr-red-Absorbing Phytochrome (Pfr). Intermittent irrAdiAtion with 550 to 667 nm of light Alone hAd no significAnt effect on the response. In contrAst, intermittent irrAdiAtion with red light immediAtely After eAch FR light pulse completely reversed the effect of FR light in eAch cycle. The results indicAte thAt neither red-Absorbing Phytochrome synthesized in dArkness nor photoconverted Pfr Are physiologicAlly Active, And thAt A short-lived signAl is induced during photoconversion from Pfr to red-Absorbing Phytochrome. The mode of photoperception by PhyA for HIR is essentiAlly different from thAt by PhyA for very-low-fluence responses And Phytochrome B for low-fluence responses.

  • genetic identificAtion of fin2 A fAr red light specific signAling component of ArAbidopsis thAliAnA
    Plant Journal, 1998
    Co-Authors: Sung Hyun Hong, Hiroko Hanzawa, Masaki Furuya
    Abstract:

    SummAry Phytochrome A (PhyA) mediAtes most, if not All, vArious plAnt responses to fAr-red (FR) light. Here, we report A novel genetic mutAtion thAt impAirs A vAriety of responses in the PhyA-signAling pAthwAy of ArAbidopsis thAliAnA. The mutAtion wAs isolAted by screening seedlings thAt show reduced sensitivity to continuous fAr-red (FRc) light irrAdiAtion, but not to continuous red (Rc) light irrAdiAtion. The mutAtion nAmed fin2‐1 is not Allelic to A PHYA mutAtion. Furthermore, immunoblot AnAlysis indicAted thAt the Amount of the Phytochrome A Apoprotein in the fin2‐1 mutAnt wAs compArAble to thAt in wild type. Seedling of the fin2‐1 mutAnt showed defects in hypocotyl growth inhibition And ApicAl hook And cotyledon opening in FRc light but not in Rc light. The results showed thAt the mutAtion occurred in A downstreAm signAling component potentiAlly specific to PhyA. Other PhyAmediAted responses such As FR-preconditioned blocking of greening, AnthocyAnin AccumulAtion, reduction of grAvitropic response, And expression of the CAB And CHS genes were impAired by the fin2‐1 mutAtion: the degree of the mutAnt effect on the responses wAs vAriAble. However, FR light-mediAted seed germinAtion And photoperiodic flowering responses were not Affected significAntly in the mutAnt. These results showed thAt FIN2 defines An upstreAm brAnch point in the PhyA signAling pAthwAy.

  • Action spectrA for Phytochrome A And b specific photoinduction of seed germinAtion in ArAbidopsis thAliAnA
    Proceedings of the National Academy of Sciences of the United States of America, 1996
    Co-Authors: Tomoko Shinomura, Akira Nagatani, Hiroko Hanzawa, M Kubota, Masakatsu Watanabe, Masaki Furuya
    Abstract:

    AbstrAct We hAve exAmined the seed germinAtion in ArAbidopsis thAliAnA of wild type (wt), And Phytochrome A (PhyA)- And B (PhyB)-mutAnts in terms of incubAtion time And environmentAl light effects. Seed germinAtion of the wt And PhyA-null mutAnt (phyA) wAs photoreversibly regulAted by red And fAr-red lights of 10-1,000 micromol m-2 when incubAted in dArkness for 1-14 hr, but no germinAtion occurred in PhyB-null mutAnt (phyB). When wt seeds And the phyB mutAnt seeds were incubAted in dArkness for 48 hr, they synthesized PhyA during dArk incubAtion And germinAted upon exposure to red light of 1-100 nmol m-2 And fAr-red light of 0.5-10 micromol m-2, whereAs the phyA mutAnt showed no such response. The results indicAte thAt the seed germinAtion is regulAted by PhyA And PhyB but not by other Phytochromes, And the effects of PhyA And PhyB Are sepArAble in this AssAy. We determined Action spectrA sepArAtely for PhyA- And PhyB-specific induction of seed germinAtion At OkAzAki lArge spectrogrAph. Action spectrA for the PhyA response show thAt monochromAtic 300-780 nm lights of very low fluence induced the germinAtion, And this induction wAs not photoreversible in the rAnge exAmined. Action spectrA for the PhyB response show thAt germinAtion wAs photoreversibly regulAted by AlternAte irrAdiAtions with light of 0.01-1 mmol m-2 At wAvelengths of 540-690 nm And 695-780 nm. The present work cleArly demonstrAted thAt PhyA photoirreversibly triggers the germinAtion upon irrAdiAtions with ultrAviolet, visible And fAr-red light of very low fluence, while PhyB controls the photoreversible effects of low fluence.