Genomic and physiological studies of early cryptochrome 1 action demonstrate roles for auxin and gibberellin in the control of hypocotyl growth by blue light.

Blue light inhibits elongation of etiolated Arabidopsis thaliana hypocotyls during the first 30 min of irradiation by a mechanism that depends on the phototropin 1 (phot1) photoreceptor. The cryptochrome 1 (cry1) photoreceptor begins to exert control after 30 min. To identify genes responsible for the cry1 phase of growth inhibition, mRNA expression profiles of cry1 and wild-type seedlings were compared using DNA microarrays. Of the roughly 420 genes found to be differentially expressed at the point of cry1 response incipience, approximately half were expressed higher and half lower in cry1 relative to the wild type. Many of the cry1-dependent genes encoded kinases, transcription factors, cell cycle regulators, cell wall metabolism enzymes, gibberellic acid (GA) biosynthesis enzymes, and auxin response factors. High-resolution growth studies supported the hypothesis that genes in the last two categories were indeed relevant to cry1-mediated growth control. Inhibiting GA4 biosynthesis with a 3beta-hydroxylase inhibitor (Ca-prohexadione) restored wild-type response kinetics in cry1 and completely suppressed its long-hypocotyl phenotype in blue light. Co-treatment of cry1 seedlings with Ca-prohexadione plus GA4 completely reversed the effects of the inhibitor, restoring the long-hypocotyl phenotype typical of the mutant. Treatment of wild-type seedlings with GA4 was not sufficient to phenocopy cry1 seedlings, but co-treatment with IAA plus GA4 produced cry1-like growth kinetics for a period of approximately 5 h. The genomic and physiological data together indicate that blue light acting through cry1 quickly affects the expression of many genes, a subset of which suppresses stem growth by repressing GA and auxin levels and/or sensitivity.

[1]  Paul Galland,et al.  Action Spectrum for Cryptochrome-Dependent Hypocotyl Growth Inhibition in Arabidopsis1 , 2002, Plant Physiology.

[2]  D. Cosgrove.  Photomodulation of growth , 1994 .

[3]  X. Q. Wang,et al.  Regulation of abscisic acid-induced stomatal closure and anion channels by guard cell AAPK kinase. , 2000, Science.

[4]  T. Imaizumi,et al.  Cryptochrome Light Signals Control Development to Suppress Auxin Sensitivity in the Moss Physcomitrella patens Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.010388. , 2002, The Plant Cell Online.

[5]  M. Ahmad,et al.  Mutations throughout an Arabidopsis blue-light photoreceptor impair blue-light-responsive anthocyanin accumulation and inhibition of hypocotyl elongation. , 1995, The Plant journal : for cell and molecular biology.

[6]  K. Folta,et al.  Photocontrol of stem growth. , 2001, Current opinion in plant biology.

[7]  Tong Zhu,et al.  Multiple transcription-factor genes are early targets of phytochrome A signaling , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[8]  K. Folta,et al.  Opposing roles of phytochrome A and phytochrome B in early cryptochrome-mediated growth inhibition. , 2001, The Plant journal : for cell and molecular biology.

[9]  J. Chory,et al.  Phytochrome B Affects Responsiveness to Gibberellins in Arabidopsis , 1996, Plant physiology.

[10]  R. Hedrich,et al.  Single guard cell recordings in intact plants: light-induced hyperpolarization of the plasma membrane. , 2001, The Plant journal : for cell and molecular biology.

[11]  K. Folta,et al.  Blue Light–Directed Destabilization of the Pea Lhcb1*4 Transcript Depends on Sequences within the 5′ Untranslated Region , 1999, Plant Cell.

[12]  W. Rademacher.  Inhibitors of Gibberellin Biosynthesis: Applications in Agriculture and Horticulture , 1991 .

[13]  M. Van Montagu,et al.  Characterization of an Arabidopsis thaliana receptor-like protein kinase gene activated by oxidative stress and pathogen attack. , 1999, The Plant journal : for cell and molecular biology.

[14]  R. M. Learned,et al.  Light Suppresses 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase Gene Expression in Arabidopsis thaliana , 1996, Plant physiology.

[15]  D J Cosgrove,et al.  Enzymes and other agents that enhance cell wall extensibility. , 1999, Annual review of plant physiology and plant molecular biology.

[16]  D. Cosgrove.  Mechanism of rapid suppression of cell expansion in cucumber hypocotyls after blue-light irradiation , 2004, Planta.

[17]  K. Folta,et al.  Phototropin 1 is required for high-fluence blue-light-mediated mRNA destabilization , 2003, Plant Molecular Biology.

[18]  G. Whitelam,et al.  Phytochromes and photomorphogenesis in Arabidopsis. , 1998, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[19]  C. Tonelli,et al.  Towards functional characterisation of the members of the R2R3-MYB gene family from Arabidopsis thaliana. , 1998, The Plant journal : for cell and molecular biology.

[20]  R. Bhalerao,et al.  Functional identification of an Arabidopsis snf4 ortholog by screening for heterologous multicopy suppressors of snf4 deficiency in yeast. , 2000, The Plant journal : for cell and molecular biology.

[21]  Hongyu Zhao,et al.  Analysis of far-red light-regulated genome expression profiles of phytochrome A pathway mutants in Arabidopsis. , 2002, The Plant journal : for cell and molecular biology.

[22]  J. B. Reid,et al.  Regulation of gibberellin 20-oxidase and gibberellin 3beta-hydroxylase transcript accumulation during De-etiolation of pea seedlings. , 1999, Plant physiology.

[23]  Eberhard Schäfer,et al.  The molecular biology of photo-regulated gene expression , 1994 .

[24]  P. Hedden,et al.  Modification of gibberellin production and plant development in Arabidopsis by sense and antisense expression of gibberellin 20-oxidase genes. , 1999, The Plant journal : for cell and molecular biology.

[25]  J. Schroeder,et al.  Strong regulation of slow anion channels and abscisic acid signaling in guard cells by phosphorylation and dephosphorylation events. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[26]  M. Estelle,et al.  Auxin transport is required for hypocotyl elongation in light-grown but not dark-grown Arabidopsis. , 1998, Plant physiology.

[27]  Z. Pei,et al.  Differential abscisic acid regulation of guard cell slow anion channels in Arabidopsis wild-type and abi1 and abi2 mutants. , 1997, The Plant cell.

[28]  S. Kay,et al.  Cryptochromes Are Required for Phytochrome Signaling to the Circadian Clock but Not for Rhythmicity , 2000, Plant Cell.

[29]  P. Quail,et al.  Phytochromes: photosensory perception and signal transduction , 1995, Science.

[30]  Hongyu Zhao,et al.  Light Control of Arabidopsis Development Entails Coordinated Regulation of Genome Expression and Cellular Pathways , 2001, The Plant Cell Online.

[31]  E. Liscum,et al.  The enhancement of phototropin-induced phototropic curvature in Arabidopsis occurs via a photoreversible phytochrome A-dependent modulation of auxin responsiveness. , 2001, Plant physiology.

[32]  J. Lockhart.  REVERSAL OF THE LIGHT INHIBITION OF PEA STEM GROWTH BY THE GIBBERELLINS. , 1956, Proceedings of the National Academy of Sciences of the United States of America.

[33]  E. Spalding.  Ion channels and the transduction of light signals. , 2000, Plant, cell & environment.

[34]  R. Bhalerao,et al.  Control of cell elongation and stress responses by steroid hormones and carbon catabolic repression in plants. , 1998, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[35]  J. Christie,et al.  Phototropins 1 and 2: versatile plant blue-light receptors. , 2002, Trends in plant science.

[36]  R. Stracke,et al.  The R2R3-MYB gene family in Arabidopsis thaliana. , 2001, Current opinion in plant biology.

[37]  J. Reed,et al.  Roles and activities of Aux/IAA proteins in Arabidopsis. , 2001, Trends in plant science.

[38]  J. Chory,et al.  A link between the light and gibberellin signaling cascades. , 2001, Developmental Cell.

[39]  A. Cashmore,et al.  Cryptochromes: blue light receptors for plants and animals. , 1999, Science.

[40]  G. J. Acton,et al.  The roles of auxin and gibberellin in reversing radiation inhibition of hypocotyl lengthening , 1974, Planta.

[41]  R. Baraldi,et al.  RESEARCH NOTE , 1995 .

[42]  S. Yamaguchi,et al.  Gibberellin biosynthesis: its regulation by endogenous and environmental signals. , 2000, Plant & cell physiology.

[43]  J. Schiefelbein,et al.  WEREWOLF, a MYB-Related Protein in Arabidopsis, Is a Position-Dependent Regulator of Epidermal Cell Patterning , 1999, Cell.

[44]  J. Frachisse,et al.  Characterization of a nitrate-permeable channel able to mediate sustained anion efflux in hypocotyl cells from Arabidopsis thaliana. , 2000, The Plant journal : for cell and molecular biology.

[45]  G. Jenkins,et al.  Extension-growth responses and expression of flavonoid biosynthesis genes in the Arabidopsis hy4 mutant , 2004, Planta.

[46]  J. B. Reid,et al.  Control of Gibberellin Levels and Gene Expression during De-Etiolation in Pea1 , 2002, Plant Physiology.

[47]  O. Leyser,et al.  Hormonal interactions in the control of Arabidopsis hypocotyl elongation. , 2000, Plant physiology.

[48]  K. Folta,et al.  Unexpected roles for cryptochrome 2 and phototropin revealed by high-resolution analysis of blue light-mediated hypocotyl growth inhibition. , 2001, The Plant journal : for cell and molecular biology.

[49]  G. Fink,et al.  A Myb homologue, ATR1, activates tryptophan gene expression in Arabidopsis. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[50]  E. Spalding,et al.  Two genetically separable phases of growth inhibition induced by blue light in Arabidopsis seedlings. , 1998, Plant physiology.

[51]  M. Caboche,et al.  Cellular Basis of Hypocotyl Growth in Arabidopsis thaliana , 1997, Plant physiology.

[52]  T. Mockler,et al.  Regulation of Arabidopsis cryptochrome 2 by blue-light-dependent phosphorylation , 2002, Nature.

[53]  S. Thomine,et al.  Anion-Channel Blockers Interfere with Auxin Responses in Dark-Grown Arabidopsis Hypocotyls , 1997, Plant physiology.

[54]  M. Straume,et al.  Effects of synergistic signaling by phytochrome A and cryptochrome1 on circadian clock-regulated catalase expression. , 1997, The Plant cell.

[55]  E. Spalding,et al.  Sequential and coordinated action of phytochromes A and B during Arabidopsis stem growth revealed by kinetic analysis. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[56]  M. Pontin,et al.  Blue light control of hypocotyl elongation in etiolated seedlings of Lactuca sativa (L.) cv. Grand Rapids related to exogenous growth regulators and endogenous IAA, GA3 and abscisic acid , 1998, Plant Growth Regulation.

[57]  Chentao Lin.  Blue Light Receptors and Signal Transduction Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.000646. , 2002, The Plant Cell Online.

[58]  J. Peng,et al.  Gibberellin Deficiency and Response Mutations Suppress the Stem Elongation Phenotype of Phytochrome-Deficient Mutants of Arabidopsis , 1997, Plant physiology.

[59]  E. Liscum,et al.  Mutations in the NPH1 locus of Arabidopsis disrupt the perception of phototropic stimuli. , 1995, The Plant cell.

[60]  P. Oeller,et al.  Arabidopsis NPH1: a protein kinase with a putative redox-sensing domain. , 1997, Science.

[61]  O. Grandjean,et al.  Phytochrome controls the number of endoreduplication cycles in the Arabidopsis thaliana hypocotyl. , 1998, The Plant journal : for cell and molecular biology.

[62]  D. Hardie,et al.  Bacterial expression of the catalytic domain of 3-hydroxy-3-methylglutaryl-CoA reductase (isoform HMGR1) from Arabidopsis thaliana, and its inactivation by phosphorylation at Ser577 by Brassica oleracea 3-hydroxy-3-methylglutaryl-CoA reductase kinase. , 1995, European journal of biochemistry.

[63]  E. Spalding,et al.  Anion channels and the stimulation of anthocyanin accumulation by blue light in Arabidopsis seedlings. , 1998, Plant physiology.

[64]  M. Nishimura,et al.  Reduction to below threshold levels of glycolate oxidase activities in transgenic tobacco enhances photoinhibition during irradiation. , 2000, Plant & cell physiology.