Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3.

By Yunde Zhao, Anna K. Hull, Neeru Gupta, Kendrick A. Goss, José M. Alonso, Joseph R. Ecker, J. Normanly, Joanne Chory, J. Celenza. Genes & Development, 2002

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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 two Arabidopsis 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.

Subfields: Molecular Biology, Plant Science

View Paper: https://www.semanticscholar.org/paper/a2c5f34accefa697eb26448450228e4564be6709

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Citations in the corpus

Conversion of tryptophan to indole-3-acetic acid by TRYPTOPHAN AMINOTRANSFERASES OF ARABIDOPSIS and YUCCAs in Arabidopsis (2011, background): “IAOx is probably not a main auxin biosynthesis intermediate, because (i) a complete elimination of IAOx production in Arabidopsis only leads to subtle growth defects (5), (ii) the enzymes CYP79B2 and -B3 seemed only to exist in a small group of plants, and (iii) there is no detectable IAOx in rice a”
The pathway of auxin biosynthesis in plants. (2012, background): “On the other hand, the transgenic Arabidopsis lines overexpressing the CYP79B2 gene have significantly elevated levels of indole glucosinolates and IAN (Mikkelsen et al., 2000; Zhao et al., 2002), although the overexpressors show a normal content of IAA (Zhao et al., 2002).”
Interdependency of Brassinosteroid and Auxin Signaling in Arabidopsis (2004, background): “1996) fail to elongate with increased temperature (Gray et al. 1998; Zhao et al. 2002).”
Auxin Control in the Formation of Adventitious Roots (2011, positive): “YUCCA1 gene encodes a flavin monooxygenase suitable for converting tryptamine in N-hydroxyl tryptamine in vitro (Zhao et al. , 2001, 2002) and belongs to a family of YUCflavin mono-oxigenases from which 4 have a role in auxin biosynthesis (Cheng et al. , 2006).”
Auxin: regulation, action, and interaction. (2005, background): “CYP79B2 overexpressors have increased IAA, IAN (Zhao et al., 2002) and indolic glucosinolate levels (Mikkelsen et al.”
Auxin biosynthesis and its role in plant development (2010, background): “RELATIONSHIPS AMONG THE PROPOSED AUXIN BIOSYNTHESIS PATHWAYS The intermediate IAOx was proposed as a shared intermediate among the CYP79B2/B3, YUC, and glucosinolate biosynthesis pathways (74) (Figure 1).”
TAA1-mediated auxin biosynthesis is essential for hormone crosstalk and plant development. (2008, background): “Mutant analysis has clearly implicated two gene families, the YUCCA (YUC) family of flavin monooxygenases (Zhao et al., 2001) and the CYP79B2/ B3 family of cytochrome P450s (Zhao et al., 2002), in auxin biosynthesis.”
Auxin control of root development. (2010, background): “Despite being the first plant hormone identified, experimental evidence detailing multiple auxin biosynthetic pathways has only recently been reported (Zhao et al. 2001; Zhao et al. 2002; Woodward and Bartel 2005; Cheng et al. 2006; Seidel et al. 2006; Normanly 2009).”
Rapid synthesis of auxin via a new tryptophan-dependent pathway is required for shade avoidance in plants. (2008, neutral): “So far, only one auxin-deficient mutant in Arabidopsis has been described to have significantly reduced free IAA levels due to mutations in enzymes involved in Trp-dependent IAA biosynthesis pathway (Zhao et al., 2002).”
PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) regulates auxin biosynthesis at high temperature (2011, background): “These phenotypes are enhanced by growth at 26 °C, suggesting a role for CYP79B2 and CYP79B3 in high-temperature–mediated auxin elevation (24).”
Gibberellin Biosynthesis and Response during Arabidopsis Seed Germination Online version contains Web-only data. Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.011650. (2003, background): “Recent work has demonstrated that these CYPs are necessary not only for indole glucosinolate synthesis but also for the formation of indoleacetic acid through indole-3-acetaldoxime (Zhao et al., 2002).”