Publications

• Auxin biosynthesis: a simple two-step pathway converts tryptophan to indole-3-acetic acid in plants.

  Zhao Y.

  Indole-3-acetic acid (IAA), the main naturally occurring auxin, is essential for almost every aspect of plant growth and development. However, only recently have studies finally established the first complete auxin biosynthesis pathway that converts tryptophan (Trp) to IAA in plants. Trp is first ... >> More

  Indole-3-acetic acid (IAA), the main naturally occurring auxin, is essential for almost every aspect of plant growth and development. However, only recently have studies finally established the first complete auxin biosynthesis pathway that converts tryptophan (Trp) to IAA in plants. Trp is first converted to indole-3-pyruvate (IPA) by the TAA family of amino transferases and subsequently IAA is produced from IPA by the YUC family of flavin monooxygenases. The two-step conversion of Trp to IAA is the main auxin biosynthesis pathway that plays an essential role in many developmental processes. << Less

  Mol Plant 5:334-338(2012) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• The main auxin biosynthesis pathway in Arabidopsis.

  Mashiguchi K., Tanaka K., Sakai T., Sugawara S., Kawaide H., Natsume M., Hanada A., Yaeno T., Shirasu K., Yao H., McSteen P., Zhao Y., Hayashi K., Kamiya Y., Kasahara H.

  The phytohormone auxin plays critical roles in the regulation of plant growth and development. Indole-3-acetic acid (IAA) has been recognized as the major auxin for more than 70 y. Although several pathways have been proposed, how auxin is synthesized in plants is still unclear. Previous genetic a ... >> More

  The phytohormone auxin plays critical roles in the regulation of plant growth and development. Indole-3-acetic acid (IAA) has been recognized as the major auxin for more than 70 y. Although several pathways have been proposed, how auxin is synthesized in plants is still unclear. Previous genetic and enzymatic studies demonstrated that both TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA) and YUCCA (YUC) flavin monooxygenase-like proteins are required for biosynthesis of IAA during plant development, but these enzymes were placed in two independent pathways. In this article, we demonstrate that the TAA family produces indole-3-pyruvic acid (IPA) and the YUC family functions in the conversion of IPA to IAA in Arabidopsis (Arabidopsis thaliana) by a quantification method of IPA using liquid chromatography-electrospray ionization-tandem MS. We further show that YUC protein expressed in Escherichia coli directly converts IPA to IAA. Indole-3-acetaldehyde is probably not a precursor of IAA in the IPA pathway. Our results indicate that YUC proteins catalyze a rate-limiting step of the IPA pathway, which is the main IAA biosynthesis pathway in Arabidopsis. << Less

  Proc. Natl. Acad. Sci. U.S.A. 108:18512-18517(2011) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• yucca6, a dominant mutation in Arabidopsis, affects auxin accumulation and auxin-related phenotypes.

  Kim J.I., Sharkhuu A., Jin J.B., Li P., Jeong J.C., Baek D., Lee S.Y., Blakeslee J.J., Murphy A.S., Bohnert H.J., Hasegawa P.M., Yun D.J., Bressan R.A.

  Auxin plays critical roles in many aspects of plant growth and development. Although a number of auxin biosynthetic pathways have been identified, their overlapping nature has prevented a clear elucidation of auxin biosynthesis. Recently, Arabidopsis (Arabidopsis thaliana) mutants with supernormal ... >> More

  Auxin plays critical roles in many aspects of plant growth and development. Although a number of auxin biosynthetic pathways have been identified, their overlapping nature has prevented a clear elucidation of auxin biosynthesis. Recently, Arabidopsis (Arabidopsis thaliana) mutants with supernormal auxin phenotypes have been reported. These mutants exhibit hyperactivation of genes belonging to the YUCCA family, encoding putative flavin monooxygenase enzymes that result in increased endogenous auxin levels. Here, we report the discovery of fertile dominant Arabidopsis hypertall1-1D and hypertall1-2D (yucca6-1D, -2D) mutants that exhibit typical auxin overproduction phenotypic alterations, such as epinastic cotyledons, increased apical dominance, and curled leaves. However, unlike other auxin overproduction mutants, yucca6 plants do not display short or hairy root phenotypes and lack morphological changes under dark conditions. In addition, yucca6-1D and yucca6-2D have extremely tall (>1 m) inflorescences with extreme apical dominance and twisted cauline leaves. Microarray analyses revealed that expression of several indole-3-acetic acid-inducible genes, including Aux/IAA, SMALL AUXIN-UP RNA, and GH3, is severalfold higher in yucca6 mutants than in the wild type. Tryptophan (Trp) analog feeding experiments and catalytic activity assays with recombinant YUCCA6 indicate that YUCCA6 is involved in a Trp-dependent auxin biosynthesis pathway. YUCCA6:GREEN FLUORESCENT PROTEIN fusion protein indicates YUCCA6 protein exhibits a nonplastidial subcellular localization in an unidentified intracellular compartment. Taken together, our results identify YUCCA6 as a functional member of the YUCCA family with unique roles in growth and development. << Less

  Plant Physiol. 145:722-735(2007) [PubMed] [EuropePMC]

• Alternative splicing of the auxin biosynthesis gene YUCCA4 determines its subcellular compartmentation.

  Kriechbaumer V., Wang P., Hawes C., Abell B.M.

  Auxin is a major growth hormone in plants, and recent studies have elucidated many of the molecular mechanisms underlying its action, including transport, perception and signal transduction. However, major gaps remain in our knowledge of auxin biosynthetic control, partly due to the complexity and ... >> More

  Auxin is a major growth hormone in plants, and recent studies have elucidated many of the molecular mechanisms underlying its action, including transport, perception and signal transduction. However, major gaps remain in our knowledge of auxin biosynthetic control, partly due to the complexity and probable redundancy of multiple pathways that involve the YUCCA family of flavin-dependent mono-oxygenases. This study reveals the differential localization of YUCCA4 alternative splice variants to the endoplasmic reticulum and the cytosol, which depends on tissue-specific splicing. One isoform is restricted to flowers, and is anchored to the cytosolic face of the endoplasmic reticulum membrane via a hydrophobic C-terminal transmembrane domain. The other isoform is present in all tissues and is distributed throughout the cytosol. These findings are consistent with previous observations of yucca4 phenotypes in flowers, and suggest a role for intracellular compartmentation in auxin biosynthesis. << Less

  Plant J. 70:292-302(2012) [PubMed] [EuropePMC]

• The biochemical mechanism of auxin biosynthesis by an Arabidopsis YUCCA flavin-containing monooxygenase.

  Dai X., Mashiguchi K., Chen Q., Kasahara H., Kamiya Y., Ojha S., Dubois J., Ballou D., Zhao Y.

  Auxin regulates every aspect of plant growth and development. Previous genetic studies demonstrated that YUCCA (YUC) flavin-containing monooxygenases (FMOs) catalyze a rate-limiting step in auxin biosynthesis and that YUCs are essential for many developmental processes. We proposed that YUCs conve ... >> More

  Auxin regulates every aspect of plant growth and development. Previous genetic studies demonstrated that YUCCA (YUC) flavin-containing monooxygenases (FMOs) catalyze a rate-limiting step in auxin biosynthesis and that YUCs are essential for many developmental processes. We proposed that YUCs convert indole-3-pyruvate (IPA) to indole-3-acetate (IAA). However, the exact biochemical mechanism of YUCs has remained elusive. Here we present the biochemical characterization of recombinant Arabidopsis YUC6. Expressed in and purified from Escherichia coli, YUC6 contains FAD as a cofactor, which has peaks at 448 nm and 376 nm in the UV-visible spectrum. We show that YUC6 uses NADPH and oxygen to convert IPA to IAA. The first step of the YUC6-catalyzed reaction is the reduction of the FAD cofactor to FADH(-) by NADPH. Subsequently, FADH(-) reacts with oxygen to form a flavin-C4a-(hydro)peroxy intermediate, which we show has a maximum absorbance at 381 nm in its UV-visible spectrum. The final chemical step is the reaction of the C4a-intermediate with IPA to produce IAA. Although the sequences of the YUC enzymes are related to those of the mammalian FMOs, which oxygenate nucleophilic substrates, YUC6 oxygenates an electrophilic substrate (IPA). Nevertheless, both classes of enzymes form quasi-stable C4a-(hydro)peroxyl FAD intermediates. The YUC6 intermediate has a half-life of ∼20 s whereas that of some FMOs is >30 min. This work reveals the catalytic mechanism of the first known plant flavin monooxygenase and provides a foundation for further investigating how YUC activities are regulated in plants. << Less

  J. Biol. Chem. 288:1448-1457(2013) [PubMed] [EuropePMC]