Yang_2008_Plant.Physiol_147_1034

Reference

Title : Inactive methyl indole-3-acetic acid ester can be hydrolyzed and activated by several esterases belonging to the AtMES esterase family of Arabidopsis - Yang_2008_Plant.Physiol_147_1034
Author(s) : Yang Y , Xu R , Ma CJ , Vlot AC , Klessig DF , Pichersky E
Ref : Plant Physiol , 147 :1034 , 2008
Abstract :

The plant hormone auxin (indole-3-acetic acid [IAA]) is found both free and conjugated to a variety of carbohydrates, amino acids, and peptides. We have recently shown that IAA could be converted to its methyl ester (MeIAA) by the Arabidopsis (Arabidopsis thaliana) enzyme IAA carboxyl methyltransferase 1. However, the presence and function of MeIAA in vivo remains unclear. Recently, it has been shown that the tobacco (Nicotiana tabacum) protein SABP2 (salicylic acid binding protein 2) hydrolyzes methyl salicylate to salicylic acid. There are 20 homologs of SABP2 in the genome of Arabidopsis, which we have named AtMES (for methyl esterases). We tested 15 of the proteins encoded by these genes in biochemical assays with various substrates and identified several candidate MeIAA esterases that could hydrolyze MeIAA. MeIAA, like IAA, exerts inhibitory activity on the growth of wild-type roots when applied exogenously. However, the roots of Arabidopsis plants carrying T-DNA insertions in the putative MeIAA esterase gene AtMES17 (At3g10870) displayed significantly decreased sensitivity to MeIAA compared with wild-type roots while remaining as sensitive to free IAA as wild-type roots. Incubating seedlings in the presence of [(14)C]MeIAA for 30 min revealed that mes17 mutants hydrolyzed only 40% of the [(14)C]MeIAA taken up by plants, whereas wild-type plants hydrolyzed 100% of absorbed [(14)C]MeIAA. Roots of Arabidopsis plants overexpressing AtMES17 showed increased sensitivity to MeIAA but not to IAA. Additionally, mes17 plants have longer hypocotyls and display increased expression of the auxin-responsive DR5:beta-glucuronidase reporter gene, suggesting a perturbation in IAA homeostasis and/or transport. mes17-1/axr1-3 double mutant plants have the same phenotype as axr1-3, suggesting MES17 acts upstream of AXR1. The protein encoded by AtMES17 had a K(m) value of 13 microm and a K(cat) value of 0.18 s(-1) for MeIAA. AtMES17 was expressed at the highest levels in shoot apex, stem, and root of Arabidopsis. Our results demonstrate that MeIAA is an inactive form of IAA, and the manifestations of MeIAA in vivo activity are due to the action of free IAA that is generated from MeIAA upon hydrolysis by one or more plant esterases.

PubMedSearch : Yang_2008_Plant.Physiol_147_1034
PubMedID: 18467465
Gene_locus related to this paper: arath-MES17 , arath-AT4G16690 , arath-AT4G37150 , arath-MES6 , arath-MES7 , arath-MES3 , arath-MES1 , arath-MES18 , arath-MES10 , arath-MES19

Related information

Substrate MeJA    MeIAA    Methyl-salicylate    Paranitrophenylacetate
Gene_locus MeJA    MeIAA    Methyl-salicylate    Paranitrophenylacetate    arath-MES17    arath-AT4G16690    arath-AT4G37150    arath-MES6    arath-MES7    arath-MES3    arath-MES1    arath-MES18    arath-MES10    arath-MES19
Family MeJA    MeIAA    Methyl-salicylate    Paranitrophenylacetate    arath-MES17    arath-AT4G16690    arath-AT4G37150    arath-MES6    arath-MES7    arath-MES3    arath-MES1    arath-MES18    arath-MES10    arath-MES19    Hydroxynitrile_lyase
Gene_locus_frgt MeJA    MeIAA    Methyl-salicylate    Paranitrophenylacetate    arath-MES17    arath-AT4G16690    arath-AT4G37150    arath-MES6    arath-MES7    arath-MES3    arath-MES1    arath-MES18    arath-MES10    arath-MES19    Hydroxynitrile_lyase    arath-MES20

Citations formats

Yang Y, Xu R, Ma CJ, Vlot AC, Klessig DF, Pichersky E (2008)
Inactive methyl indole-3-acetic acid ester can be hydrolyzed and activated by several esterases belonging to the AtMES esterase family of Arabidopsis
Plant Physiol 147 :1034

Yang Y, Xu R, Ma CJ, Vlot AC, Klessig DF, Pichersky E (2008)
Plant Physiol 147 :1034