Methyl jasmonate inhibition of root growth and induction of a leaf protein are decreased in an Arabidopsis thaliana mutant.

Abstract

Jasmonic acid and its methyl ester, methyl jasmonate (MeJA), are plant signaling molecules that affect plant growth and gene expression. Primary root growth of wild-type Arabidopsis thaliana seedlings was inhibited 50% when seedlings were grown on agar medium containing 0.1 IAMMeJA. An ethyl methanesulfonate mutant (jarn) with decreased sensitivity to MeJA inhibition of root elongation was isolated and characterized. Genetic data indicated the trait was recessive and controlled by a single Mendelian factor. MeJAinduced polypeptides were detected in Arabidopsis leaves by antiserum to a MeJA-inducible vegetative storage protein from soybean. The induction of these proteins by MeJA in the mutant was at least 4-fold less in jar] compared to wild type. In contrast, seeds ofjarl plants were more sensitive than wild type to inhibition of germination by abscisic acid. These results suggest that the defect in jar) affects a general jasmonate response pathway, which may regulate multiple genes in different plant organs.Jasmonate is an endogenous plant compound that affects growth and was recently recognized for its ability to induce the expression of specific plant genes. Methyl jasmonate (MeJA), the methyl ester ofjasmonic acid (JA), is one of the few plant compounds that is effective as a vapor at low concentrations, inducing tomato leaf proteinase inhibitors (1) and soybean leaf vegetative storage proteins (VSPs) (2). These two protein classes are also wound-inducible and recent results indicate that MeJA induces the phytoalexin plant defense pathway in several species (3). This evidence suggests that jasmonate may be an important stress-signaling molecule in plants.Jasmonate is derived from the lipoxygenase-dependent oxidation of linolenic acid (4). By analogy with the production of various eicosanoids involved in animal stress signaling (e.g., prostaglandins), it has been suggested that JA arises from the release of cell membrane fatty acids through the action of lipase in response to wounding or autolytic events (5, 6). MeJA also has pheromone activity in at least one insect (7) and is found in certain fungi. Thus, jasmonate is of general biological interest.Evidence that de novo synthesis ofjasmonate plays a role in regulating soybean VSP genes in response to wounding was recently reported (8). However, little is known about the signal-transduction mechanism for jasmonate action in plants. Mutants in phytohormone synthesis and response have received increased attention in recent years. Such mutants not only provide a better understanding of plant growth regulator function but, with emerging technology, may provide a strategy for the isolation of genes involved in plant hormone signaling pathways (9, 10). The purpose of this study was to find and characterize Arabidopsis mutants with an altered response to MeJA. METHODS 6837The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely...

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“…In addition to the SAR mutants, mutants defective in their response to ethylene (etrl, ein2) (Bleecker et al, 1988;Guzman and Ecker, 1990) or jasmonic acid (jar1) (Staswick et al, 1992) have been characterized. The ethylene-insensitive mutants have been used to show that SAR signal transduction is ethylene independent (Lawton et al, 1994.…”

ArabidopsisPEN3/PDR8, an ATP Binding Cassette Transporter, Contributes to Nonhost Resistance to Inappropriate Pathogens That Enter by Direct Penetration

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