Flavonoids act as negative regulators of auxin transport in vivo in arabidopsis.

Polar transport of the plant hormone auxin controls many aspects of plant growth and development. A number of synthetic compounds have been shown to block the process of auxin transport by inhibition of the auxin efflux carrier complex. These synthetic auxin transport inhibitors may act by mimicking endogenous molecules. Flavonoids, a class of secondary plant metabolic compounds, have been suggested to be auxin transport inhibitors based on their in vitro activity. The hypothesis that flavonoids regulate auxin transport in vivo was tested in Arabidopsis by comparing wild-type (WT) and transparent testa (tt4) plants with a mutation in the gene encoding the first enzyme in flavonoid biosynthesis, chalcone synthase. In a comparison between tt4 and WT plants, phenotypic differences were observed, including three times as many secondary inflorescence stems, reduced plant height, decreased stem diameter, and increased secondary root development. Growth of WT Arabidopsis plants on naringenin, a biosynthetic precursor to those flavonoids with auxin transport inhibitor activity in vitro, leads to a reduction in root growth and gravitropism, similar to the effects of synthetic auxin transport inhibitors. Analyses of auxin transport in the inflorescence and hypocotyl of independent tt4 alleles indicate that auxin transport is elevated in plants with a tt4 mutation. In hypocotyls of tt4, this elevated transport is reversed when flavonoids are synthesized by growth of plants on the flavonoid precursor, naringenin. These results are consistent with a role for flavonoids as endogenous regulators of auxin transport.

[1]  M. Iacobucci,et al.  A null mutation in the first enzyme of flavonoid biosynthesis does not affect male fertility in Arabidopsis. , 1996, The Plant cell.

[2]  P. K. Smith,et al.  Measurement of protein using bicinchoninic acid. , 1985, Analytical biochemistry.

[3]  J Chory,et al.  Mutations in the DET1 gene affect cell-type-specific expression of light-regulated genes and chloroplast development in Arabidopsis , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[4]  M. Sakuta.  Transcriptional Control of Chalcone Synthase by Environmental Stimuli , 2000, Journal of Plant Research.

[5]  P. J. Davies,et al.  Evidence for Three Different Systems of Movement of Indoleacetic Acid in Intact Roots of Phaseolus coccineus , 1975 .

[6]  G. Stenlid.  Effects of Flavonoids on the Polar Transport of Auxins , 1976 .

[7]  R Chen,et al.  Arabidopsis thalianaのAGRAVITROPIC 1遺伝子は極性オーキシン輸送の流出キャリアの構成員をコード化する , 1998 .

[8]  J. Cohen,et al.  A Rapid and Simple Procedure for Purification of Indole-3-Acetic Acid Prior to GC-SIM-MS Analysis. , 1988, Plant physiology.

[9]  J. Chappell.  The Biochemistry and Molecular Biology of Isoprenoid Metabolism , 1995, Plant physiology.

[10]  D. Söll,et al.  The RCN1-encoded A subunit of protein phosphatase 2A increases phosphatase activity in vivo. , 1999, The Plant journal : for cell and molecular biology.

[11]  A. Boudet,et al.  Relations polyphénols — croissance: Mise en évidence d'un effet inhibiteur des composés phénoliques sur le transport polarisé de l'auxine , 1977 .

[12]  J. Slovin,et al.  Rethinking Auxin Biosynthesis and Metabolism , 1995, Plant physiology.

[13]  D. Saslowsky,et al.  An allelic series for the chalcone synthase locus in Arabidopsis. , 2000, Gene.

[14]  P. Rubery,et al.  Naturally Occurring Auxin Transport Regulators , 1988, Science.

[15]  B. W. Shirley.  Flavonoid biosynthesis: ‘new’ functions for an ‘old’ pathway , 1996 .

[16]  P. Rubery.  Phytotropins: receptors and endogenous ligands. , 1990, Symposia of the Society for Experimental Biology.

[17]  H. Spaink,et al.  Auxin transport inhibition precedes root nodule formation in white clover roots and is regulated by flavonoids and derivatives of chitin oligosaccharides. , 1998, The Plant journal : for cell and molecular biology.

[18]  G. Stenlid.  The Effects of Flavonoid Compounds on Oxidative Phosphorylation and on the Enzymatic Destruction of Indoleacetic Acid , 1963 .

[19]  C. Fischer,et al.  Induction of Zygotic Polyembryos in Wheat: Influence of Auxin Polar Transport. , 1997, The Plant cell.

[20]  G. Muday,et al.  Basipetal auxin transport is required for gravitropism in roots of Arabidopsis. , 2000, Plant physiology.

[21]  F. Ausubel,et al.  Transcriptional regulation of the Arabidopsis thaliana chalcone synthase gene , 1988, Molecular and cellular biology.

[22]  G. Muday.  Interactions Between the Actin Cytoskeleton and an Auxin Transport Protein , 2000 .

[23]  R. Dixon,et al.  Developmental and environmental regulation of a bean chalcone synthase promoter in transgenic tobacco. , 1990, The Plant cell.

[24]  G. Muday,et al.  Cytoplasmic Orientation of the Naphthylphthalamic Acid-Binding Protein in Zucchini Plasma Membrane Vesicles , 1996, Plant physiology.

[25]  J. Slovin,et al.  C(6)-[benzene ring]-indole-3-acetic Acid: a new internal standard for quantitative mass spectral analysis of indole-3-acetic Acid in plants. , 1986, Plant physiology.

[26]  C. Bell,et al.  Requirement of the Auxin Polar Transport System in Early Stages of Arabidopsis Floral Bud Formation. , 1991, The Plant cell.

[27]  T. Bisseling,et al.  In situ localization of chalcone synthase mRNA in pea root nodule development. , 1992 .

[28]  T. Bisseling,et al.  Early nodulin genes are induced in alfalfa root outgrowths elicited by auxin transport inhibitors. , 1989, Proceedings of the National Academy of Sciences of the United States of America.

[29]  L. Gälweiler,et al.  PIN-pointing the molecular basis of auxin transport. , 1999, Current opinion in plant biology.

[30]  Alan Marchant,et al.  AUX1 regulates root gravitropism in Arabidopsis by facilitating auxin uptake within root apical tissues , 1999, The EMBO journal.

[31]  P. Bernasconi.  Effect of synthetic and natural protein tyrosine kinase inhibitors on auxin efflux in zucchini (Cucurbita pepo) hypocotyls , 1996 .

[32]  H. Goodman,et al.  Regulation of Flavonoid Biosynthetic Genes in Germinating Arabidopsis Seedlings. , 1992, The Plant cell.

[33]  A. Murphy,et al.  Flavonoid accumulation patterns of transparent testa mutants of arabidopsis. , 2001, Plant physiology.

[34]  M. Estelle,et al.  Reduced naphthylphthalamic acid binding in the tir3 mutant of Arabidopsis is associated with a reduction in polar auxin transport and diverse morphological defects. , 1997, The Plant cell.

[35]  G. F. Katekar.  Inhibitors of the geotropic response in plants: A correlation of molecular structures , 1976 .

[36]  G. Jenkins,et al.  Isolation of Arabidopsis mutants altered in the light-regulation of chalcone synthase gene expression using a transgenic screening approach. , 1995, The Plant journal : for cell and molecular biology.

[37]  S. May,et al.  Going the distance with auxin: unravelling the molecular basis of auxin transport. , 1998, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[38]  A. Galston,et al.  Isolation from Peas of Co-Factors and Inhibitors of Indolyl-3-Acetic Acid Oxidase , 1962, Nature.

[39]  P. Masson,et al.  The arabidopsis thaliana AGRAVITROPIC 1 gene encodes a component of the polar-auxin-transport efflux carrier. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[40]  D. Söll,et al.  A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis. , 1996, The EMBO journal.

[41]  S. Tsurumi,et al.  Transport of 14C-lableled indoleacetic acid in Vicia root segments , 1978 .

[42]  P. Rubery,et al.  Auxin Transport and Its Regulation by Flavonoids , 1990 .

[43]  A. Murphy,et al.  Regulation of auxin transport by aminopeptidases and endogenous flavonoids , 2000, Planta.

[44]  G. Storz,et al.  Analysis of Arabidopsis mutants deficient in flavonoid biosynthesis. , 1995, The Plant journal : for cell and molecular biology.

[45]  X. Deng,et al.  LIGHT CONTROL OF SEEDLING DEVELOPMENT. , 1996, Annual review of plant physiology and plant molecular biology.

[46]  G. Muday,et al.  Inhibition of auxin movement from the shoot into the root inhibits lateral root development in Arabidopsis. , 1998, Plant physiology.

[47]  A. Murphy,et al.  A New Vertical Mesh Transfer Technique for Metal-Tolerance Studies in Arabidopsis (Ecotypic Variation and Copper-Sensitive Mutants) , 1995, Plant physiology.

[48]  D. Smith,et al.  An inhibitor of indoleacetic acid oxidase from pea tips. , 1961, Plant physiology.