Modulating plant hormones by enzyme action

Westfall, Corey S.; Herrmann, Jonathan; Chen, Qing-Feng; Wang, Shiping; Jez, Joseph M.

doi:10.4161/psb.5.12.13941

Cited by 84 publications

(53 citation statements)

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“…2b). Thus, even though these IAA-amido synthetases exhibit partially overlapping enzyme activities in vitro 15,16 , our genetic results strongly indicate that their functions are not simply redundant in vivo .…”

Section: Resultsmentioning

confidence: 67%

“…Elevated IAA-Asp levels in vas2 mutants may be a metabolic feedback response to the high levels of free IAA and catalysed in vivo by VAS2–GH3.17 homologues, including GH3.2, GH3.3, GH3.4 and GH3.5. All four IAA-amido synthetases have been shown to conjugate IAA to Asp (refs 15,16). In contrast, VAS2–GH3.17 does not efficiently conjugate IAA to Asp (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Local auxin metabolism regulates environment-induced hypocotyl elongation

et al. 2016

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A hallmark of plants is their adaptability of size and form in response to widely fluctuating environments. The metabolism and redistribution of the phytohormone auxin play pivotal roles in establishing active auxin gradients and resulting cellular differentiation. In Arabidopsis thaliana, cotyledons and leaves synthesize indole-3-acetic acid (IAA) from tryptophan through indole-3-pyruvic acid (3-IPA) in response to vegetational shade. This newly synthesized auxin moves to the hypocotyl where it induces elongation of hypocotyl cells. Here we show that loss of function of VAS2 (IAA-amido synthetase Gretchen Hagen 3 (GH3).17) leads to increases in free IAA at the expense of IAA-Glu (IAA-glutamate) in the hypocotyl epidermis. This active IAA elicits shade- and high temperature-induced hypocotyl elongation largely independently of 3-IPA-mediated IAA biosynthesis in cotyledons. Our results reveal an unexpected capacity of local auxin metabolism to modulate the homeostasis and spatial distribution of free auxin in specialized organs such as hypocotyls in response to shade and high temperature.

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Section: Resultsmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Local auxin metabolism regulates environment-induced hypocotyl elongation

et al. 2016

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“…Multiple studies highlight the diverse roles for GH3 acyl acid amido synthetases as modulators of jasmonate and auxin phytohormones (25)(26)(27)(28)(29)(30)(31)(32)(33), but the potential function of these proteins as modifiers of herbicides in plants has not been fully examined. Motivated by the possibility that the phenoxyalkanoic acid auxinic herbicides 2,4-D and 2,4-DB mimic IAA and IBA (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In plants, the Gretchen Hagen 3 (GH3) acyl acid amido synthetases conjugate amino acids to carboxylic acid-containing hormones, such as jasmonic acid, IAA, and the endogenous auxin indole-3-butyric acid (IBA), to regulate plant growth, seed development, light signaling, and pathogen responses (25)(26)(27)(28)(29)(30)(31)(32)(33). GH3 proteins catalyze the adenylation of the carboxylate on these molecules to form an acyl-AMP intermediate, which undergoes nucleophilic attack by an amino acid to yield the conjugated product (28,30).…”

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confidence: 99%

Modification of auxinic phenoxyalkanoic acid herbicides by the acyl acid amido synthetase GH3.15 from Arabidopsis

Sherp¹,

Lee²,

Schraft³

et al. 2018

Journal of Biological Chemistry

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Herbicide-resistance traits are the most widely used agriculture biotechnology products. Yet, to maintain their effectiveness and to mitigate selection of herbicide-resistant weeds, the discovery of new resistance traits that use different chemical modes of action is essential. In plants, the Gretchen Hagen 3 (GH3) acyl acid amido synthetases catalyze the conjugation of amino acids to jasmonate and auxin phytohormones. This reaction chemistry has not been explored as a possible approach for herbicide modification and inactivation. Here, we examined a set of Arabidopsis GH3 proteins that use the auxins indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) as substrates along with the corresponding auxinic phenoxyalkanoic acid herbicides 2,4-dichlorophenoxylacetic acid (2,4-D) and 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB). The IBA-specific AtGH3.15 protein displayed high catalytic activity with 2,4-DB, which was comparable to its activity with IBA. Screening of phenoxyalkanoic and phenylalkyl acids indicated that side-chain length of alkanoic and alkyl acids is a key feature of AtGH3.15's substrate preference. The X-ray crystal structure of the AtGH3.15·2,4-DB complex revealed how the herbicide binds in the active site. In root elongation assays, Arabidopsis AtGH3.15-knockout and -overexpression lines grown in the presence of 2,4-DB exhibited hypersensitivity and tolerance, respectively, indicating that the AtGH3.15-catalyzed modification inactivates 2,4-DB. These findings suggest a potential use for AtGH3.15, and perhaps other GH3 proteins, as herbicide-modifying enzymes that employ a mode of action different from those of currently available herbicide-resistance traits.

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“…IAA can be reversibly conjugated via ester linkages to glucose by UDP-glucosyl transferases to produce indole-3-acetyl-1-glucosyl ester (IAGlc) (Jackson et al , 2001). Members of the GRETCHEN HAGEN3 (GH3) family of acyl amido synthetases mediate conjugation of IAA with amino acids (Staswick et al , 2005; Westfall et al , 2011). IAA amino acid conjugates are regarded as either reversible or irreversible IAA metabolites based on in vitro activity and in planta feeding assays (Östin et al , 1998; Kowalczyk & Sandberg, 2001).…”

Section: Introductionmentioning

confidence: 99%

Conifers exhibit a characteristic inactivation of auxin to maintain tissue homeostasis

Brunoni

Collani

Casanova‐Sáez

et al. 2019

Preprint

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Dynamic regulation of the levels of the natural auxin, indol-3-acetic acid (IAA), is essential to coordinate most of the physiological and developmental processes and responses to environmental changes. Oxidation of IAA is a major pathway to control auxin concentrations in Arabidopsis and, along with IAA conjugation, to respond to perturbation of IAA homeostasis. However, these regulatory mechanisms are still poorly investigated in conifers. To reduce this gap of knowledge, we investigated the different contribution of the IAA inactivation pathways in conifers.• Mass spectrometry-based quantification of IAA metabolites under steady state conditions and after perturbation was investigated to evaluate IAA homeostasis in conifers. Putative Picea abies GH3 genes (PaGH3) were identified by a comprehensive phylogenetic analysis including Arabidopsis and basal land plants. Auxin-inducible PaGH3 genes were identified by expression analysis and their IAA-conjugating activity was explored.• Compared to Arabidopsis, oxidative and conjugative pathways differentially contribute to reduce IAA levels in conifers. We demonstrated that the oxidation pathway plays a marginal role in controlling IAA homeostasis in spruce. On the other hand, an excess of IAA rapidly activates GH3-mediated irreversible conjugation pathways.• Taken together, these data indicate that a diversification of IAA inactivation mechanisms evolved specifically in conifers.

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Modulating plant hormones by enzyme action

Abstract: Addendum to: Chen Q, Westfall CS, Hicks LM, Wang S, Jez JM. Kinetic basis for the conjugation of auxin by a GH3 family indole-acetic acid-amido synthetase.

Cited by 84 publications

References 50 publications

Local auxin metabolism regulates environment-induced hypocotyl elongation

Local auxin metabolism regulates environment-induced hypocotyl elongation

Modification of auxinic phenoxyalkanoic acid herbicides by the acyl acid amido synthetase GH3.15 from Arabidopsis

Conifers exhibit a characteristic inactivation of auxin to maintain tissue homeostasis

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