Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3
- Yunde Zhao1,2,5,6,
- Anna K. Hull3,5,7,
- Neeru R. Gupta3,
- Kendrick A. Goss3,
- José Alonso2,8,
- Joseph R. Ecker2,
- Jennifer Normanly4,
- Joanne Chory1,2, and
- John L. Celenza3,9
- 1Howard Hughes Medical Institute and 2Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA; 3Department of Biology, Boston University, Boston, Massachusetts 02215, USA; 4Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA
Abstract
The plant hormone auxin regulates many aspects of plant growth and development. Although several auxin biosynthetic pathways have been proposed, none of these pathways has been precisely defined at the molecular level. Here we provide in planta evidence that the twoArabidopsis cytochrome P450s, CYP79B2 and CYP79B3, which convert tryptophan (Trp) to indole-3-acetaldoxime (IAOx) in vitro, are critical enzymes in auxin biosynthesis in vivo. IAOx is thus implicated as an important intermediate in auxin biosynthesis. Plants overexpressing CYP79B2 contain elevated levels of free auxin and display auxin overproduction phenotypes. Conversely, cyp79B2 cyp79B3 double mutants have reduced levels of IAA and show growth defects consistent with partial auxin deficiency. Together with previous work on YUCCA, a flavin monooxygenase also implicated in IAOx production, and nitrilases that convert indole-3-acetonitrile to auxin, this work provides a framework for further dissecting auxin biosynthetic pathways and their regulation.
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Footnotes
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↵5 These authors contributed equally.
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Present addresses: 6Division of Biological Sciences, The University of California at San Diego, La Jolla, CA 92093-0116, USA; 7Fraunhofer-CMB USA, Newark, DE 19711, USA; 8Department of Genetics, North Carolina State University, Raleigh, NC 27695, USA.
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↵9 Corresponding author.
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E-MAIL celenza{at}bu.edu; FAX (617) 353-6340.
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Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.1035402.
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- Received August 22, 2002.
- Accepted October 11, 2002.
- Cold Spring Harbor Laboratory Press
