title: Molecular and biochemical characterization of the jasmonic acid methyltransferase gene from black cottonwood (Populus trichocarpa).
abstract: Methyl jasmonate is a metabolite known to be produced by many plants and has roles in diverse biological processes. It is biosynthesized by the action of S-adenosyl-l-methionine:jasmonic acid carboxyl methyltransferase (JMT), which belongs to the SABATH family of methyltransferases. Herein is reported the isolation and biochemical characterization of a JMT gene from black cottonwood (Populus trichocarpa). The genome of P. trichocarpa contains 28 SABATH genes (PtSABATH1 to PtSABATH28). Recombinant PtSABATH3 expressed in Escherichia coli showed the highest level of activity with jasmonic acid (JA) among carboxylic acids tested. It was therefore renamed PtJMT1. PtJMT1 also displayed activity with benzoic acid (BA), with which the activity was about 22% of that with JA. PtSABATH2 and PtSABATH4 were most similar to PtJMT1 among all PtSABATHs. However, neither of them had activity with JA. The apparent Km values of PtJMT1 using JA and BA as substrate were 175μM and 341μM, respectively. Mutation of Ser-153 and Asn-361, two residues in the active site of PtJMT1, to Tyr and Ser respectively, led to higher specific activity with BA than with JA. Homology-based structural modeling indicated that substrate alignment, in which Asn-361 is involved, plays a role in determining the substrate specificity of PtJMT1. In the leaves of young seedlings of black cottonwood, the expression of PtJMT1 was induced by plant defense signal molecules methyl jasmonate and salicylic acid and a fungal elicitor alamethicin, suggesting that PtJMT1 may have a role in plant defense against biotic stresses. Phylogenetic analysis suggests that PtJMT1 shares a common ancestor with the Arabidopsis JMT, and functional divergence of these two apparent JMT orthologs has occurred since the split of poplar and Arabidopsis lineages.
authors.affiliation: Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhao
authors.forename: Jianzhuang
authors.initials: J
authors.lastname: Yao
authors.forename: Minta
authors.initials: M
authors.lastname: Chaiprasongsuk
authors.forename: Guanglin
authors.initials: G
authors.lastname: Li
authors.forename: Ju
authors.initials: J
authors.lastname: Guan
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Tschaplinski
authors.forename: Hong
authors.initials: H
authors.lastname: Guo
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
mesh_terms: D000085:Acetates / Q000378:metabolism / Q000494:pharmacology; D000408:Alamethicin / Q000494:pharmacology; D019817:Benzoic Acid / Q000378:metabolism; D055162:Biocatalysis / Q000187:drug effects; D020134:Catalytic Domain / Q000235:genetics; D003517:Cyclopentanes / Q000378:metabolism / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008670:Metals / Q000494:pharmacology; D008780:Methyltransferases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D005810:Multigene Family / Q000235:genetics*; D009154:Mutation; D054883:Oxylipins / Q000378:metabolism / Q000494:pharmacology; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D032107:Populus / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020156:Salicylic Acid / Q000494:pharmacology; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D008670:Metals; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011994:Recombinant Proteins; D000408:Alamethicin; C011006:jasmonic acid; D019817:Benzoic Acid; C072239:methyl jasmonate; D008780:Methyltransferases; C425043:jasmonic acid carboxyl methyltransferase; D020156:Salicylic Acid
keywords: Benzoic acid; Poplar; Populus trichocarpa; SABATH family; Salicaceae; Substrate-specificity evolution