Coordination of auxin and ethylene biosynthesis by the aminotransferase VAS1

Journal name:
Nature Chemical Biology
Volume:
9,
Pages:
244–246
Year published:
DOI:
doi:10.1038/nchembio.1178
Received
Accepted
Published online

We identify an Arabidopsis pyridoxal-phosphate–dependent aminotransferase, VAS1, whose loss-of-function simultaneously increases amounts of the phytohormone auxin and the ethylene precursor 1-aminocyclopropane-1-carboxylate. VAS1 uses the ethylene biosynthetic intermediate methionine as an amino donor and the auxin biosynthetic intermediate indole-3-pyruvic acid as an amino acceptor to produce L-tryptophan and 2-oxo-4-methylthiobutyric acid. Our data indicate that VAS1 serves key roles in coordinating the amounts of these two vital hormones.

At a glance

Figures

  1. VAS1 functions in auxin metabolism, downstream of TAA1/SAV3 but upstream of YUCs.
    Figure 1: VAS1 functions in auxin metabolism, downstream of TAA1/SAV3 but upstream of YUCs.

    (a) vas1 rescued the sav3 hypocotyl elongation defect in response to shade (n = 15). The plants were grown on 1/2 MS plates and kept under white light (WC) for 5 d and then remained in WC for 4 d or transferred to shade for 4 d. (b) vas1 plants had longer petioles than wild-type plants under both WC and shade conditions (n = 30). The petiole length of the first set of true leaves are shown. (c) vas1 accumulated larger amounts of IAA in both WC and shade (n = 3). (d) vas1 accumulated larger amounts of 3-IPA in both WC and shade (n = 3). Results are shown as mean ± s.e.m. *P < 0.05, **P < 0.01 and ***P < 0.001 (two-tailed Student's t-test). The comparison is made between wild-type Col plants and mutants under the same growth conditions and same treatment.

  2. VAS1 encodes a methionine-specific aminotransferase and model for VAS1 metabolic regulation of auxin and ethylene biosynthesis.
    Figure 2: VAS1 encodes a methionine-specific aminotransferase and model for VAS1 metabolic regulation of auxin and ethylene biosynthesis.

    (a) Diagram of VAS1 genomic DNA sequence, with exons indicated by the black boxes. Mutations of each vas1 mutant allele are shown. (b) UV-based chromatograms for VAS1 in vitro reactions. L-tryptophan formed in the presence of 3-IPA, L-methionine and PLP. Chromatographic profiles of L-tryptophan (1), the reaction mixture minus VAS1 (2), and the reaction mixture containing VAS1 (3) monitored at 254 nm. The two peaks for 3-IPA are the keto and enol tautomers of 3-IPA (verified by NMR spectroscopy). AU, absorbance units. (c) Reaction diagram for a metabolic hub linking auxin and ethylene biosynthesis through VAS1. SAM, S-adenosyl-L-methionine; MTA, methylthioadenosine; MTR, methylthioribose; MTR-1-P, methylthioribose phosphate.

  3. Increased ACC in vas1 mutants leads to exaggerated petiole elongation.
    Figure 3: Increased ACC in vas1 mutants leads to exaggerated petiole elongation.

    (a) vas1-2 sav3-1 and vas1-2 seedlings had increased ACC in both white light (WC) and shade (n = 3) compared to wild-type plants. (b) Ethylene signal transduction mutation ein2-5 fully suppressed the exaggerated petiole elongation of vas1-2 and vas1-2 sav3-1 (n = 28). **P < 0.01 and ***P < 0.001 (two-tailed Student's t-test).

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Author information

  1. These authors contributed equally to this manuscript.

    • Zuyu Zheng &
    • Yongxia Guo

Affiliations

  1. Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, California, USA.

    • Zuyu Zheng,
    • Joseph P Noel &
    • Joanne Chory
  2. Plant Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA.

    • Zuyu Zheng &
    • Joanne Chory
  3. Jack H. Skirball Center for Chemical Biology and Proteomics, Salk Institute for Biological Studies, La Jolla, California, USA.

    • Yongxia Guo &
    • Joseph P Noel
  4. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden.

    • Ondřej Novák &
    • Karin Ljung
  5. Laboratory of Growth Regulators, Faculty of Science, Palacký University, Olomouc, Czech Republic.

    • Ondřej Novák
  6. Institute of Experimental Botany, Academy of Science of Czech Republic, Olomouc, Czech Republic.

    • Ondřej Novák
  7. Section of Cell and Developmental Biology, University of California–San Diego, La Jolla, California.

    • Xinhua Dai &
    • Yunde Zhao

Contributions

Z.Z. and Y.G. designed research, performed research, analyzed data and wrote the paper. O.N. and K.L. measured the amount of IAA and 3-IPA and analyzed data. X.D. and Y.Z. provided yuc1-163 yuc4 seeds. J.P.N. and J.C. designed research, analyzed data and wrote the paper.

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The authors declare no competing financial interests.

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