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.

• Removal of phosphoglycolate in hyperthermophilic archaea.

  Michimori Y., Izaki R., Su Y., Fukuyama Y., Shimamura S., Nishimura K., Miwa Y., Hamakita S., Shimosaka T., Makino Y., Takeno R., Sato T., Beppu H., Cann I., Kanai T., Nunoura T., Atomi H.

  Many organisms that utilize the Calvin-Benson-Bassham (CBB) cycle for autotrophic growth harbor metabolic pathways to remove and/or salvage 2-phosphoglycolate, the product of the oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). It has been presumed that the occurren ... >> More

  Many organisms that utilize the Calvin-Benson-Bassham (CBB) cycle for autotrophic growth harbor metabolic pathways to remove and/or salvage 2-phosphoglycolate, the product of the oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). It has been presumed that the occurrence of 2-phosphoglycolate salvage is linked to the CBB cycle, and in particular, the C2 pathway to the CBB cycle and oxygenic photosynthesis. Here, we examined 2-phosphoglycolate salvage in the hyperthermophilic archaeon <i>Thermococcus kodakarensis</i>, an obligate anaerobe that harbors a Rubisco that functions in the pentose bisphosphate pathway. <i>T. kodakarensis</i> harbors enzymes that have the potential to convert 2-phosphoglycolate to glycine and serine, and their genes were identified by biochemical and/or genetic analyses. 2-phosphoglycolate phosphatase activity increased 1.6-fold when cells were grown under microaerobic conditions compared to anaerobic conditions. Among two candidates, TK1734 encoded a phosphatase specific for 2-phosphoglycolate, and the enzyme was responsible for 80% of the 2-phosphoglycolate phosphatase activity in <i>T. kodakarensis</i> cells. The TK1734 disruption strain displayed growth impairment under microaerobic conditions, which was relieved upon addition of sodium sulfide. In addition, glycolate was detected in the medium when <i>T. kodakarensis</i> was grown under microaerobic conditions. The results suggest that <i>T. kodakarensis</i> removes 2-phosphoglycolate via a phosphatase reaction followed by secretion of glycolate to the medium. As the Rubisco in <i>T. kodakarensis</i> functions in the pentose bisphosphate pathway and not in the CBB cycle, mechanisms to remove 2-phosphoglycolate in this archaeon emerged independent of the CBB cycle. << Less

  Proc Natl Acad Sci U S A 121:e2311390121-e2311390121(2024) [PubMed] [EuropePMC]

  This publication is cited by 21 other entries.

• vanishing tassel2 encodes a grass-specific tryptophan aminotransferase required for vegetative and reproductive development in maize.

  Phillips K.A., Skirpan A.L., Liu X., Christensen A., Slewinski T.L., Hudson C., Barazesh S., Cohen J.D., Malcomber S., McSteen P.

  Auxin plays a fundamental role in organogenesis in plants. Multiple pathways for auxin biosynthesis have been proposed, but none of the predicted pathways are completely understood. Here, we report the positional cloning and characterization of the vanishing tassel2 (vt2) gene of maize (Zea mays). ... >> More

  Auxin plays a fundamental role in organogenesis in plants. Multiple pathways for auxin biosynthesis have been proposed, but none of the predicted pathways are completely understood. Here, we report the positional cloning and characterization of the vanishing tassel2 (vt2) gene of maize (Zea mays). Phylogenetic analyses indicate that vt2 is a co-ortholog of TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 (TAA1), which converts Trp to indole-3-pyruvic acid in one of four hypothesized Trp-dependent auxin biosynthesis pathways. Unlike single mutations in TAA1, which cause subtle morphological phenotypes in Arabidopsis thaliana, vt2 mutants have dramatic effects on vegetative and reproductive development. vt2 mutants share many similarities with sparse inflorescence1 (spi1) mutants in maize. spi1 is proposed to encode an enzyme in the tryptamine pathway for Trp-dependent auxin biosynthesis, although this biochemical activity has recently been questioned. Surprisingly, spi1 vt2 double mutants had only a slightly more severe phenotype than vt2 single mutants. Furthermore, both spi1 and vt2 single mutants exhibited a reduction in free auxin levels, but the spi1 vt2 double mutants did not have a further reduction compared with vt2 single mutants. Therefore, both spi1 and vt2 function in auxin biosynthesis in maize, possibly in the same pathway rather than independently as previously proposed. << Less

  Plant Cell 23:550-566(2011) [PubMed] [EuropePMC]

• 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.

• Rapid synthesis of auxin via a new tryptophan-dependent pathway is required for shade avoidance in plants.

  Tao Y., Ferrer J.L., Ljung K., Pojer F., Hong F., Long J.A., Li L., Moreno J.E., Bowman M.E., Ivans L.J., Cheng Y., Lim J., Zhao Y., Ballare C.L., Sandberg G., Noel J.P., Chory J.

  Plants grown at high densities perceive a decrease in the red to far-red (R:FR) ratio of incoming light, resulting from absorption of red light by canopy leaves and reflection of far-red light from neighboring plants. These changes in light quality trigger a series of responses known collectively ... >> More

  Plants grown at high densities perceive a decrease in the red to far-red (R:FR) ratio of incoming light, resulting from absorption of red light by canopy leaves and reflection of far-red light from neighboring plants. These changes in light quality trigger a series of responses known collectively as the shade avoidance syndrome. During shade avoidance, stems elongate at the expense of leaf and storage organ expansion, branching is inhibited, and flowering is accelerated. We identified several loci in Arabidopsis, mutations in which lead to plants defective in multiple shade avoidance responses. Here we describe TAA1, an aminotransferase, and show that TAA1 catalyzes the formation of indole-3-pyruvic acid (IPA) from L-tryptophan (L-Trp), the first step in a previously proposed, but uncharacterized, auxin biosynthetic pathway. This pathway is rapidly deployed to synthesize auxin at the high levels required to initiate the multiple changes in body plan associated with shade avoidance. << Less

  Cell 133:164-176(2008) [PubMed] [EuropePMC]