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Preference of Arabidopsis thaliana GH3.5 acyl amido synthetase for growth versus defense hormone acyl substrates is dictated by concentration of amino acid substrate aspartate.
Phytochemistry. 2017 Nov; 143:19-28.P

Abstract

The GH3 family of adenylating enzymes conjugate acyl substrates such as the growth hormone indole-3-acetic acid (IAA) to amino acids via a two-step reaction of acyl substrate adenylation followed by amino acid conjugation. Arabidopsis thaliana GH3.5 was previously shown to be unusual in that it could adenylate both IAA and the defense hormone salicylic acid (SA, 2-hydroxybenzoate). Our detailed studies of the kinetics of GH3.5 on a variety of auxin and benzoate substrates provides insight into the acyl preference and reaction mechanism of GH3.5. For example, we found GH3.5 activity on substituted benzoates is not defined by the substitution position as it is for GH3.12/PBS3. Most importantly, we show that GH3.5 strongly prefers Asp as the amino acid conjugate and that the concentration of Asp dictates the functional activity of GH3.5 on IAA vs. SA. Not only is Asp used in amino acid biosynthesis, but it also plays an important role in nitrogen mobilization and in the production of downstream metabolites, including pipecolic acid which propagates defense systemically. During active growth, [IAA] and [Asp] are high and the catalytic efficiency (kcat/Km) of GH3.5 for IAA is 360-fold higher than with SA. GH3.5 is expressed under these conditions and conversion of IAA to inactive IAA-Asp would provide fine spatial and temporal control over local auxin developmental responses. By contrast, [SA] is dramatically elevated in response to (hemi)-biotrophic pathogens which also induce GH3.5 expression. Under these conditions, [Asp] is low and GH3.5 has equal affinity (Km) for SA and IAA with similar catalytic efficiencies. However, the concentration of IAA tends to be very low, well below the Km for IAA. Therefore, GH3.5 catalyzed formation of SA-Asp would occur, fine-tuning localized defensive responses through conversion of active free SA to SA-Asp. Taken together, we show how GH3.5, with dual activity on IAA and SA, can integrate cellular metabolic status via Asp to provide fine control of growth vs. defense outcomes and hormone homeostasis.

Authors+Show Affiliations

Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA.Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA.Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA. Electronic address: mwildermuth@berkeley.edu.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

28743075

Citation

Mackelprang, Rebecca, et al. "Preference of Arabidopsis Thaliana GH3.5 Acyl Amido Synthetase for Growth Versus Defense Hormone Acyl Substrates Is Dictated By Concentration of Amino Acid Substrate Aspartate." Phytochemistry, vol. 143, 2017, pp. 19-28.
Mackelprang R, Okrent RA, Wildermuth MC. Preference of Arabidopsis thaliana GH3.5 acyl amido synthetase for growth versus defense hormone acyl substrates is dictated by concentration of amino acid substrate aspartate. Phytochemistry. 2017;143:19-28.
Mackelprang, R., Okrent, R. A., & Wildermuth, M. C. (2017). Preference of Arabidopsis thaliana GH3.5 acyl amido synthetase for growth versus defense hormone acyl substrates is dictated by concentration of amino acid substrate aspartate. Phytochemistry, 143, 19-28. https://doi.org/10.1016/j.phytochem.2017.07.001
Mackelprang R, Okrent RA, Wildermuth MC. Preference of Arabidopsis Thaliana GH3.5 Acyl Amido Synthetase for Growth Versus Defense Hormone Acyl Substrates Is Dictated By Concentration of Amino Acid Substrate Aspartate. Phytochemistry. 2017;143:19-28. PubMed PMID: 28743075.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Preference of Arabidopsis thaliana GH3.5 acyl amido synthetase for growth versus defense hormone acyl substrates is dictated by concentration of amino acid substrate aspartate. AU - Mackelprang,Rebecca, AU - Okrent,Rachel A, AU - Wildermuth,Mary C, Y1 - 2017/07/23/ PY - 2017/03/30/received PY - 2017/06/29/revised PY - 2017/07/04/accepted PY - 2017/7/26/pubmed PY - 2017/10/3/medline PY - 2017/7/26/entrez KW - 1-Naphthaleneacetic acid (PubChem CID: 6862) KW - 4-Hydroxybenzoic acid (PubChem CID: 135) KW - Acyl amido synthetase KW - Adenyl transferase KW - Arabidopsis thaliana (Brassicaceae) KW - Aspartate KW - GH3 KW - Hormone crosstalk KW - Hormone homeostasis KW - Indole-3-acetic acid KW - Indole-3-acetic acid (PubChem CID: 802) KW - Indole-3-butryic acid (PubChem CID: 8617) KW - Indole-3-carboxylic acid (PubChem CID: 69867) KW - Indole-3-pyruvic acid (PubChem CID: 803) KW - Indolyl-3-aspartic acid (PubChem CID: 446620) KW - L-aspartic acid (PubChem CID: 5960) KW - Phenylacetic acid (PubChem CID: 999) KW - Salicylic acid KW - Salicylic acid (PubChem CID: 338) KW - Salicyloylaspartic acid (PubChem CID: 4520077) SP - 19 EP - 28 JF - Phytochemistry JO - Phytochemistry VL - 143 N2 - The GH3 family of adenylating enzymes conjugate acyl substrates such as the growth hormone indole-3-acetic acid (IAA) to amino acids via a two-step reaction of acyl substrate adenylation followed by amino acid conjugation. Arabidopsis thaliana GH3.5 was previously shown to be unusual in that it could adenylate both IAA and the defense hormone salicylic acid (SA, 2-hydroxybenzoate). Our detailed studies of the kinetics of GH3.5 on a variety of auxin and benzoate substrates provides insight into the acyl preference and reaction mechanism of GH3.5. For example, we found GH3.5 activity on substituted benzoates is not defined by the substitution position as it is for GH3.12/PBS3. Most importantly, we show that GH3.5 strongly prefers Asp as the amino acid conjugate and that the concentration of Asp dictates the functional activity of GH3.5 on IAA vs. SA. Not only is Asp used in amino acid biosynthesis, but it also plays an important role in nitrogen mobilization and in the production of downstream metabolites, including pipecolic acid which propagates defense systemically. During active growth, [IAA] and [Asp] are high and the catalytic efficiency (kcat/Km) of GH3.5 for IAA is 360-fold higher than with SA. GH3.5 is expressed under these conditions and conversion of IAA to inactive IAA-Asp would provide fine spatial and temporal control over local auxin developmental responses. By contrast, [SA] is dramatically elevated in response to (hemi)-biotrophic pathogens which also induce GH3.5 expression. Under these conditions, [Asp] is low and GH3.5 has equal affinity (Km) for SA and IAA with similar catalytic efficiencies. However, the concentration of IAA tends to be very low, well below the Km for IAA. Therefore, GH3.5 catalyzed formation of SA-Asp would occur, fine-tuning localized defensive responses through conversion of active free SA to SA-Asp. Taken together, we show how GH3.5, with dual activity on IAA and SA, can integrate cellular metabolic status via Asp to provide fine control of growth vs. defense outcomes and hormone homeostasis. SN - 1873-3700 UR - https://www.unboundmedicine.com/medline/citation/28743075/Preference_of_Arabidopsis_thaliana_GH3_5_acyl_amido_synthetase_for_growth_versus_defense_hormone_acyl_substrates_is_dictated_by_concentration_of_amino_acid_substrate_aspartate_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0031-9422(17)30251-0 DB - PRIME DP - Unbound Medicine ER -