Jasmonic acid carboxyl methyltransferase: A key enzyme for jasmonate-regulated plant responses

Abstract

Methyl jasmonate is a plant volatile that acts as an important cellular regulator mediating diverse developmental processes and defense responses. We have cloned the novel gene JMT encoding an S-adenosyl-L-methionine:jasmonic acid carboxyl methyltransferase (JMT) from Arabidopsis thaliana. Recombinant JMT protein expressed in Escherichia coli catalyzed the formation of methyl jasmonate from jasmonic acid with K m value of 38.5 M. JMT RNA was not detected in young seedlings but was detected in rosettes, cauline leaves, and developing flowers. In addition, expression of the gene was induced both locally and systemically by wounding or methyl jasmonate treatment. This result suggests that JMT can perceive and respond to local and systemic signals generated by external stimuli, and that the signals may include methyl jasmonate itself. Transgenic Arabidopsis overexpressing JMT had a 3-fold elevated level of endogenous methyl jasmonate without altering jasmonic acid content. The transgenic plants exhibited constitutive expression of jasmonate-responsive genes, including VSP and PDF1.2. Furthermore, the transgenic plants showed enhanced level of resistance against the virulent fungus Botrytis cinerea. Thus, our data suggest that the jasmonic acid carboxyl methyltransferase is a key enzyme for jasmonate-regulated plant responses. Activation of JMT expression leads to production of methyl jasmonate that could act as an intracellular regulator, a diffusible intercellular signal transducer, and an airborne signal mediating intra-and interplant communications.

Biosynthesis and emission of insect-induced methyl salicylate and methyl benzoate from rice

“…SAMT and BAMT belong to a protein family called the SABATH [7]. In addition to SA and BA, other known carboxylic acid substrates of the SABATH family include jasmonic acid (JA) [34], indole-3-acetic acid [31,44e46], gibberellic acids [41], farnesoic acid [42], cinnamic acid and p-coumaric acid [16] and loganic acid [21]. Other members of the SABATH family are involved in caffeine biosynthesis by catalyzing nitrogen methylation [25].…”

Biosynthesis of plant‐derived flavor compounds

“…Interestingly, a group of N-methyltransferases involved in biosynthesis of the alkaloid caffeine, including theobromine synthase, share sequence similarity with the SA and BA carboxyl methyltransferases . These enzymes were therefore grouped into a new class of methyltransferases designated the SABATH methyltransferases, and this family now also includes jasmonic acid methyltransferase (Seo et al, 2001), indole-acetic acid methyltransferase and cinnamic/p-coumaric acid methyltransferase (Kapteyn et al, 2007). The recently obtained three-dimensional structure of C. breweri SA carboxyl methyltransferase , combined with in silico modeling of the active site pocket in the Nicotiana suaveolens and S. floribunda enzymes (Pott et al, 2004), also indicates that these enzymes have a unique structure that is distinct from those of unrelated methyltransferases found in plants .…”

Des dérivés d’acides gras dans la résistance des plantes aux attaques microbiennes : à la recherche d’acyle hydrolases impliquées dans la synthèse des oxylipines

“…Enfin, la chaîne latérale est raccourcie par trois cycles de beta-oxydation pour conduire à l'AJ. L'AOPD, l'AJ, et son ester méthylique, le méthyle jasmonate (MJ), possèdent des propriétés de signalisation similaires pour certaines réponses physiologiques [18] mais clairement distinctes pour d'autres [19][20][21]. Les enzymes de biosynthèse conduisant de l'acide linolénique à l'AOPD (LOX, AOS, et AOC) sont chloroplastiques, les étapes ultérieures sont probablement catalysées dans les peroxysomes [22].…”

“…Des plantes chez lesquelles on a surexprimé ou au contraire inhibé des enzymes de biosynthèse d'oxylipines ont été obtenues et présentent une augmentation [20] ou une diminution de la résistance à différents agents pathogènes [29,30]. Les conséquences de la sur-ou sousexpression d'un gène de 9-Lox sur la résistance du tabac à Phythophthora ont été exposées par M.-T. Esquerré-Tuguayé au cours du colloque.…”