Jasmonic Acid Carboxyl Methyltransferase Research Articles

Endogenous Hormone Levels and Transcriptomic Analysis Reveal the Mechanisms of Bulbil Initiation in Pinellia ternata.

Pinellia ternata is a medicinal plant that has important pharmacological value, and the bulbils serve as the primary reproductive organ; however, the mechanisms underlying bulbil initiation remain unclear. Here, we characterized bulbil development via histological, transcriptomic, and targeted metabolomic analyses to unearth the intricate relationship between hormones, genes, and bulbil development. The results show that the bulbils initiate growth from the leaf axillary meristem (AM). In this stage, jasmonic acid (JA), abscisic acid (ABA), isopentenyl adenosine (IPA), and salicylic acid (SA) were highly enriched, while indole-3-acetic acid (IAA), zeatin, methyl jasmonate (MeJA), and 5-dexoxystrigol (5-DS) were notably decreased. Through OPLS-DA analysis, SA has emerged as the most crucial factor in initiating and positively regulating bulbil formation. Furthermore, a strong association between IPA and SA was observed during bulbil initiation. The transcriptional changes in IPT (Isopentenyltransferase), CRE1 (Cytokinin Response 1), A-ARR (Type-A Arabidopsis Response Regulator), B-ARR (Type-B Arabidopsis Response Regulator), AUX1 (Auxin Resistant 1), ARF (Auxin Response Factor), AUX/IAA (Auxin/Indole-3-acetic acid), GH3 (Gretchen Hagen 3), SAUR (Small Auxin Up RNA), GA2ox (Gibberellin 2-oxidase), GA20ox (Gibberellin 20-oxidase), AOS (Allene oxide synthase), AOC (Allene oxide cyclase), OPR (Oxophytodienoate Reductase), JMT (JA carboxy l Methyltransferase), COI1 (Coronatine Insensitive 1), JAZ (Jasmonate ZIM-domain), MYC2 (Myelocytomatosis 2), D27 (DWARF27), SMAX (Suppressor of MAX2), PAL (Phenylalanine Ammonia-Lyase), ICS (Isochorismate Synthase), NPR1 (Non-expressor of Pathogenesis-related Genes1), TGA (TGACG Sequence-specific Binding), PR-1 (Pathogenesis-related), MCSU (Molybdenium Cofactor Sulfurase), PP2C (Protein Phosphatase 2C), and SnRK (Sucrose Non-fermenting-related Protein Kinase 2) were highly correlated with hormone concentrations, indicating that bulbil initiation is coordinately controlled by multiple phytohormones. Notably, eight TFs (transcription factors) that regulate AM initiation have been identified as pivotal regulators of bulbil formation. Among these, WUS (WUSCHEL), CLV (CLAVATA), ATH1 (Arabidopsis Thaliana Homeobox Gene 1), and RAX (Regulator of Axillary meristems) have been observed to exhibit elevated expression levels. Conversely, LEAFY demonstrated contrasting expression patterns. The intricate expression profiles of these TFs are closely associated with the upregulated expression of KNOX(KNOTTED-like homeobox), suggesting a intricate regulatory network underlying the complex process of bulbil initiation. This study offers a profound understanding of the bulbil initiation process and could potentially aid in refining molecular breeding techniques specific to P. ternata.

Functional characterisation of Artemisia annua jasmonic acid carboxyl methyltransferase: a key enzyme enhancing artemisinin biosynthesis.

Overexpression of Artemisia annua jasmonic acid carboxyl methyltransferase (AaJMT) leads to enhanced artemisinin content in Artemisia annua. Artemisinin-based combination therapies remain the sole deterrent against deadly disease malaria and Artemisia annua remains the only natural producer of artemisinin. In this study, the 1101bp gene S-adenosyl-L-methionine (SAM): Artemisia annua jasmonic acid carboxyl methyltransferase (AaJMT), was characterised from A. annua, which converts jasmonic acid (JA) to methyl jasmonate (MeJA). From phylogenetic analysis, we confirmed that AaJMT shares a common ancestor with Arabidopsis thaliana, Eutrema japonica and has a close homology with JMT of Camellia sinensis. Further, the Clustal Omega depicted that the conserved motif I, motif III and motif SSSS (serine) required to bind SAM and JA, respectively, are present in AaJMT. The relative expression of AaJMT was induced by wounding, MeJA and salicylic acid (SA) treatments. Additionally, we found that the recombinant AaJMT protein catalyses the synthesis of MeJA from JA with a Km value of 37.16µM. Moreover, site-directed mutagenesis of serine-151 in motif SSSS to tyrosine, asparagine-10 to threonine and glutamine-25 to histidine abolished the enzyme activity of AaJMT, thus indicating their determining role in JA substrate binding. The GC-MS analysis validated that mutant proteins of AaJMT were unable to convert JA into MeJA. Finally, the artemisinin biosynthetic and trichome developmental genes were upregulated in AaJMT overexpression transgenic lines, which in turn increased the artemisinin content.

Exogenous methyl jasmonate enhanced the antioxidant capacity of Malus baccata by stimulating jasmonate signalling under suboptimal low root-zone temperature

Methyl jasmonate (MeJA) has been documented to mitigate the oxidative stress caused by abiotic triggers. In this study, we investigated the mechanism through which exogenous MeJA alleviates oxidative damage in the roots of Malus baccata under a suboptimal low root-zone temperature. A suboptimal low root-zone temperature promoted increases in the activity and transcription of allene oxide synthase (AOS) and jasmonic acid carboxyl methyltransferase (JMT), elevated the levels of endogenous jasmonic acid (JA), MeJA and jasmonate isoleucine (JA-Ile), and induced the accumulation of malondialdehyde (MDA) and reactive oxygen species (ROS). The addition of exogenous MeJA further increased the JA (1 h, 12–24 h), MeJA (1–24 h), and JA-Ile (1–6 h) contents and enhanced the activities and transcription of lipoxygenase (LOX) and JMT. The upregulated expression of JASMONATE ZIM-DOMAIN (JAZ) and MdMYC2 indicated that suboptimal low root-zone temperature could activate JA signalling in roots, and exogenous MeJA could further strengthen JA signalling under low-temperature stress. Exogenous MeJA alleviated oxidative damage to stressed roots by enhancing ascorbate–glutathione (AsA–GSH) cycle activity. In addition, pre-treatment with phenidone (an inhibitor of lipoxygenase) exerted the opposite effects to those induced by exogenous MeJA treatment. These findings indicated that exogenous MeJA enhanced antioxidant systems and detoxified ROS by regulating JA signalling and thereby protected M. baccata roots from damage caused by suboptimal low root-zone temperature stress.

A Genetically Engineered Escherichia coli for Potential Utilization in Fungal Smut Disease Control.

Sporisorium scitamineum, the basidiomycetous fungus that causes sugarcane smut and leads to severe losses in sugarcane quantity and quality, undergoes sexual mating to form dikaryotic hyphae capable of invading the host cane. Therefore, suppressing dikaryotic hyphae formation would potentially be an effective way to prevent host infection by the smut fungus, and the following disease symptom developments. The phytohormone methyl jasmonate (MeJA) has been shown to induce plant defenses against insects and microbial pathogens. In this study, we will verify that the exogenous addition of MeJA-suppressed dikaryotic hyphae formation in S. scitamineum and Ustilago maydis under in vitro culture conditions, and the maize smut symptom caused by U. maydis, could be effectively suppressed by MeJA in a pot experiment. We constructed an Escherichia coli-expressing plant JMT gene, encoding a jasmonic acid carboxyl methyl transferase that catalyzes conversion from jasmonic acid (JA) to MeJA. By GC-MS, we will confirm that the transformed E. coli, designated as the pJMT strain, was able to produce MeJA in the presence of JA and S-adenosyl-L-methionine (SAM as methyl donor). Furthermore, the pJMT strain was able to suppress S. scitamineum filamentous growth under in vitro culture conditions. It waits to further optimize JMT expression under field conditions in order to utilize the pJMT strain as a biocontrol agent (BCA) of sugarcane smut disease. Overall, our study provides a potentially novel method for controlling crop fungal diseases by boosting phytohormone biosynthesis.

Leaf Removal Impacted Jasmonic Acid Metabolism and AsA-GSH in the Roots of Malus baccata (L.) Borkh. under Suboptimal Low Root-Zone Temperatures

In the early growing season in northern China, suboptimal low root-zone temperatures is a common abiotic stress that impairs root function and leaf development in fruit trees. In this study, we investigate the physiological role of leaves in jasmonate metabolism and the capacity of scavenging reactive oxygen species in Malus baccata (L.) Borkh. roots under suboptimal low root-zone temperatures. In the presence of intact leaves, suboptimal low root-zone temperatures significantly increased allene oxide synthase (AOS), jasmonate-resistant 1 (JAR), and jasmonic acid carboxyl methyltransferase (JMT) activities and transcription in jasmonate biosynthesis. Meanwhile, elevated endogenous jasmonic acid (JA), methyl jasmonate (MeJA), and jasmonate-isoleucine (JA-Ile) contents were also observed, as were significantly decreased glutathione reductase and dehydroascorbate reductase activities and AsA/DHA and GSH/GSSG ratios. Conversely, leaf removal substantially reduced AOS, JMT, and JAR activities and transcription at most time points and JA (6–24 h), MeJA (1–24 h), and JA-Ile (1–24 h) levels in roots, affecting key enzymes in the AsA–GSH cycle and the AsA/DHA and GSH/GSSG ratios in response to low-temperature treatment, as a result of a significant increase in malondialdehyde content. Thus, leaves are crucial for jasmonate metabolism in roots under suboptimal low root-zone temperatures, with leaf removal exacerbating root oxidative stress by altering JA signaling and AsA–GSH cycle activity.

Molecular and Biochemical Characterization of Jasmonic Acid Carboxyl Methyltransferase Involved in Aroma Compound Production of Methyl Jasmonate during Black Tea Processing.

Methyl jasmonate (MeJA), a volatile organic compound, is a principal flowery aromatic compound in tea. During the processing of black tea, MeJA is produced by jasmonic acid carboxyl methyltransferase (JMT) of the jasmonic acid (JA) substrate, forming a specific floral fragrance. CsJMT was cloned from tea leaves; the three-dimensional structure of CsJMT was predicted. Enzyme activity was identified, and protein purification was investigated. Site-directed deletions revealed that N-10, S-22, and Q-25 residues in the beginning amino acids played a key functional role in enzyme activity. The expression patterns of CsJMT in tea organs differed; the highest expression of CsJMT was observed in the fermentation process of black tea. These results aid in further understanding the synthesis of MeJA during black tea processing, which is crucial for improving black tea quality using specific fragrances and could be applied to the aromatic compound regulation and tea breeding improvement in further studies.

Biosynthesis of orchid-like volatile methyl jasmonate in tea (Camellia sinensis) leaves in response to multiple stresses during the shaking process of oolong tea

Methyl jasmonate (MeJA), a significant fatty acid derivative, contributes to the main floral aroma of oolong tea. However, in tea plants, the mechanism of MeJA biosynthesis and the enzymes that participate in its formation is still unclear. In this study, the full length of the first jasmonic acid carboxyl methyltransferase (JMT) gene from Camellia sinensis was amplified and the biochemical function of the recombinant C. sinensis JMT (CsJMT) protein was studied after coexpression in Escherichia coli. The recombinant CsJMT protein could transfer the methyl groups to jasmonic acid to produce orchid-like volatile 1R, 2R-MeJA in vitro. Volatile 1R, 2R-MeJA was detected by gas chromatography–mass spectrometry during the shaking process of oolong tea, and the accumulation of 1R, 2R-MeJA was found to correlate with CsJMT expression. Further investigation showed that the mechanical injury and low-temperature stress could significantly induce CsJMT expression and MeJA accumulation after harvest. These results demonstrated that CsJMT catalyzed the production of MeJA in tea plants and provided a basis for studying the formation and accumulation of orchid-like volatile MeJA during the shaking process of oolong tea.

Biochemical characterization of the jasmonic acid methyltransferase gene from wasabi (Eutrema japonicum).

Methyl jasmonate and jasmonic acid play important roles as signaling molecules in regulating plant development and stress-related responses. Previous studies have shown that jasmonic acid carboxyl methyltransferase (JMT), which belongs to the SABATH methyltransferase gene family, catalyzes the transfer of methyl groups from S-adenosyl-L-methionine to the carboxyl groups of jasmonic acid. In the present study, we used RNA-seq analysis to identify a putative JMT gene, EujJMT, in wasabi (Eutrema japonicum). The EujJMT proteins showed the highest similarity (89% identity) to JMT proteins of Brassica rapa. Functional characterization of a recombinant EujJMT protein expressed in Escherichia coli showed the highest level of activity with jasmonic acid among the different carboxylic acids tested. The apparent Km value of EujJMT using jasmonic acid as substrate was 62.6 µM, which is comparable to the values of known JMTs. Phylogenetic analysis suggested that EujJMT shares a common ancestor with the JMTs of Arabidopsis and Brassica species and that the strict substrate specificity toward jasmonic acid is conserved among Brassicaceae JMTs.

Triple-localized WHIRLY2 Influences Leaf Senescence and Silique Development via Carbon Allocation.

Coordination of gene expression in mitochondria, plastids, and nucleus is critical for plant development and survival. Although WHIRLY2 (WHY2) is involved in mitochondrial genome repair and affects the DNA copy number of the mitochondrial genome, the detailed mechanism of action of the WHY2 protein is still elusive. In this study, we found that WHY2 was triple-localized among the mitochondria, plastids, and the nucleus during Arabidopsis (Arabidopsis thaliana) aging. Overexpressing WHY2 increased starch granule numbers in chloroplasts of pericarp cells, showing a partially dry, yellowing silique and early senescence leaves. Accordingly, WHY2 protein could directly activate the expression of jasmonic acid carboxyl methyltransferase and senescence associated gene 29 (SWEET15) gene expression and repress SWEET11 gene expression in the nucleus, leading to alteration of starch accumulation and transport in pericarp cells. In contrast, loss of WHY2 decreased starch and sugar content in pericarp cells but promoted starch accumulation in leaves and seeds. These phenotypes of WHY2-overexpressing plants were enhanced in response to methyl jasmonate. Our results suggest that WHY2 in plastids, mitochondria, and the nucleus plays a vital role in alteration of carbon reallocation from maternal tissue to filial tissue.

The expression characteristics of methyl jasmonate biosynthesis–related genes in Cymbidium faberi and influence of heterologous expression of CfJMT in Petunia hybrida

Cymbidium faberi Rolfe (Orchidaceae) is an herbaceous plant native to China, where it has a long history of cultivation owing to its beautiful flower pattern and floral fragrance. Previously, we conducted a transcriptome analysis of the flower and vegetative buds to elucidate the mechanisms of flower development in C. faberi. In the present study, we found nine secondary metabolic pathways through the KEGG pathway database that were related to the biosynthesis of methyl jasmonate (MeJA) and other volatile organic compounds. qRT-PCR was performed to analyze the expression levels of four key genes in the MeJA pathway. Among these, CfJMT (jasmonic acid carboxyl methyltransferase) had higher transcript levels in sepals, petals and labella than in other tissues. CfJMT was cloned from the petals of full-bloom flowers of C. faberi. The predicted CfJMT protein sequence contains conserved jasmonic acid methyl transferase-7 domains, indicating that it belongs to the SABATH protein family. The CfJMT coding sequence driven by the CaMV35S promoter was successfully transformed into Petunia hybrida through an Agrobacterium-mediated method. Although MeJA could not be detected in either wild-type or transgenic petunia plants, the leaves of the transgenic plants were smaller than those of wild-type plants and pollen development was abnormal. These results indicate that heterologous expression of CfJMT may change the levels of endogenous jasmonic acid and other hormones, but that the content of MeJA is not increased significantly by transformation with CfJMT alone. Thus, other related genes and regulation factors may play important roles in this process.

Transcriptomic profiling of the flower scent biosynthesis pathway of Cymbidium faberi Rolfe and functional characterization of its jasmonic acid carboxyl methyltransferase gene

BackgroundCymbidium faberi, one of the most famous oriental orchids, has a distinct flower scent, which increases its economic value. However, the molecular mechanism of the flower scent biosynthesis was unclear prior to this study. Methyl jasmonate (MeJA) is one of the main volatile organic compounds (VOC) produced by the flowers of C. faberi. In this study, unigene 79,363 from comparative transcriptome analysis was selected for further investigation.ResultsA transcriptome comparison between blooming and withered flowers of C. faberi yielded a total of 9409 differentially expressed genes (DEGs), 558 of which were assigned to 258 pathways. The top ten pathways included α-linolenic acid metabolism, pyruvate metabolism and fatty acid degradation, which contributed to the conversion of α-linolenic acid to MeJA. One of the DEGs, jasmonic acid carboxyl methyltransferase (CfJMT, Unigene 79,363) was highly expressed in the blooming flower of C. faberi, but was barely detected in leaves and roots. Although the ectopic expression of CfJMT in tomato could not increase the MeJA content, the expression levels of endogenous MeJA biosynthesis genes were influenced, especially in the wound treatment, indicating that CfJMT may participate in the response to abiotic stresses.ConclusionThis study provides a basis for elucidating the molecular mechanism of flower scent biosynthesis in C. faberi, which is beneficial for the genetically informed breeding of new cultivars of the economically valuable oriental orchids.

Molecular Characterization and Overexpression of SmJMT Increases the Production of Phenolic Acids in Salvia miltiorrhiza.

Jasmonic acid (JA) carboxyl methyltransferase (JMT), a key enzyme in jasmonate-regulated plant responses, may be involved in plant defense and development by methylating JA to MeJA, thus influencing the concentrations of MeJA in plant. In this study, we isolated the JMT gene from Salvia miltiorrhiza, an important medicinal plant widely used to treat cardiovascular disease. We present a genetic manipulation strategy to enhance the production of phenolic acids by overexpresion SmJMT in S. miltiorrhiza. Global transcriptomic analysis using RNA sequencing showed that the expression levels of genes involved in the biosynthesis pathway of phenolic acids and MeJA were upregulated in the overexpression lines. In addition, the levels of endogenous MeJA, and the accumulation of rosmarinic acid (RA) and salvianolic acid (Sal B), as well as the concentrations of total phenolics and total flavonoids in transgenic lines, were significantly elevated compared with the untransformed control. Our results demonstrate that overexpression of SmJMT promotes the production of phenolic acids through simultaneously activating genes encoding key enzymes involved in the biosynthesis pathway of phenolic acids and enhancing the endogenous MeJA levels in S. miltiorrhiza.

Molecular mechanisms underlying Grateloupia imbricata (Rhodophyta) carposporogenesis induced by methyl jasmonate.

When applied invitro, methyl jasmonate is sensed by the red seaweed Grateloupia imbricate, substantially and visually affecting its carposporogenesis. However, although there is some understanding of the morphological changes induced by methyl jasmonate invitro, little is known about the genes that are involved in red seaweed carposporogenesis and how their protein products act. For the work reported herein, the expression of genes in red seaweed that encode enzymes involved in the synthesis of methyl jasmonate (jasmonic acid carboxyl methyl transferase and a putative methyl transferase) was monitored. Additionally the genes involved in oxidation (cytochrome P450 and WD40), jasmonate synthesis, signal transduction, and regulation of reactive oxygen species (MYB), and reproduction (ornithine decarboxylase) were monitored. To determine when or if the aforementioned genes were expressed during cystocarp development, fertilized and fertile thalli were exposed to methyl jasmonate and gene expression was measured after 24 and 48h. The results showed that methyl jasmonate promoted differential gene expression in fertilized thalli by 24h and upregulated expression of the ornithine decarboxylase gene only by 48h in fertile thalli (0.75±003 copies·μL-1 at 24h vs. 1.11±0.04 copies·μL-1 at 48h). We conclude that Ornithine decarboxylase expression involves methyl jasmonate signaling as well as development and maturation of cystocarps.

Methyl jasmonate-dependent senescence of cotyledons in Ipomoea nil

Jasmonic acid methyl ester (JAMe) has been recently shown to play a crucial role in many physiological processes. In this paper, we focused on cotyledon senescence in Ipomoea nil and revealed that JAMe and darkness are the main factors stimulating the process examined. What is more, we showed that mefenamic acid (a jasmonate biosynthesis inhibitor) reverses the stimulatory effect of darkness on senescence. In plants growing under dark conditions, stimulation of JASMONIC ACID CARBOXYL METHYLTRANSFERASE (InJMT) expression and, consequently, an increase in JAMe content, have been observed. In turn, the level of jasmonic acid (JA) gradually decreased. Moreover, dark-grown seedlings demonstrated a lower PSII functional activity and a reduced chlorophyll content and autofluorescence. All of these data suggest that JAMe is a signal molecule controlling the senescence of cotyledons in I. nil.

Auxin increases the InJMT expression and the level of JAMe – inhibitor of flower induction in Ipomoea nil

Interactions among jasmonates and auxin in the photoperiodic flower induction of a short-day plant <em>Ipomoea nil</em> were examined. Therefore, we measured changes in jasmonic acid (JA) and jasmonic acid methyl ester (JAMe) levels in the cotyledons of <em>I. nil</em> during the inductive night, as well as the effects of indole-3-acetic acid (IAA) on their content. We noticed an interesting result, that IAA applied on the cotyledons of <em>I. nil</em> is an effective stimulator of JAMe production in seedlings cultivated under inductive night conditions. IAA treatment also significantly increased the transcriptional activity of <em>InJMT</em> (<em>JASMONIC ACID CARBOXYL METHYLTRANSFERASE</em>), while did not affect the expression of JA biosynthesis genes (lipoxyganease, allene oxide synthase, 12-oxophytodienoate reductase). These data, as well as the results of our previous research, suggest that exogenous IAA participates in <em>I. nil</em> flower induction process by stimulating <em>InJMT</em> expression and, as a consequence of that, enhancing the level of JAMe, a flowering inhibitor.

Jasmonic acid carboxyl methyltransferase regulates development and herbivory-induced defense response in rice.

Jasmonic acid (JA) and related metabolites play a key role in plant defense and growth. JA carboxyl methyltransferase (JMT) may be involved in plant defense and development by methylating JA to methyl jasmonate (MeJA) and thus influencing the concentrations of JA and related metabolites. However, no JMT gene has been well characterized in monocotyledon defense and development at the molecular level. After we cloned a rice JMT gene, OsJMT1, whose encoding protein was localized in the cytosol, we found that the recombinant OsJMT1 protein catalyzed JA to MeJA. OsJMT1 is up-regulated in response to infestation with the brown planthopper (BPH; Nilaparvata lugens). Plants in which OsJMT1 had been overexpressed (oe-JMT plants) showed reduced height and yield. These oe-JMT plants also exhibited increased MeJA levels but reduced levels of herbivore-induced JA and jasmonoyl-isoleucine (JA-Ile). The oe-JMT plants were more attractive to BPH female adults but showed increased resistance to BPH nymphs, probably owing to the different responses of BPH female adults and nymphs to the changes in levels of H2 O2 and MeJA in oe-JMT plants. These results indicate that OsJMT1, by altering levels of JA and related metabolites, plays a role in regulating plant development and herbivore-induced defense responses in rice.

Efficient Development of Transgenic Cabbage with Jasmonic Acid Carboxyl Methyltransferase (JMT) Gene Based on PMI/Mannose Selection System

Efficient Development of Transgenic Cabbage with Jasmonic Acid Carboxyl Methyltransferase (JMT) Gene Based on PMI/Mannose Selection System

Comparative analysis of chemical compositions between non-transgenic soybean seeds and those from plants over-expressing AtJMT, the gene for jasmonic acid carboxyl methyltransferase

Transgenic overexpression of the Arabidopsis gene for jasmonic acid carboxyl methyltransferase (AtJMT) is involved in regulating jasmonate-related plant responses. To examine its role in the compositional profile of soybean (Glycine max), we compared the seeds from field-grown plants that over-express AtJMT with those of the non-transgenic, wild-type (WT) counterpart. Our analysis of chemical compositions included proximates, amino acids, fatty acids, isoflavones, and antinutrients. Overexpression of AtJMT in the seeds resulted in decreased amounts of tryptophan, palmitic acid, linolenic acid, and stachyose, but increased levels of gadoleic acid and genistein. In particular, seeds from the transgenic soybeans contained 120.0–130.5% more genistein and 60.5–82.1% less stachyose than the WT. A separate evaluation of ingredient values showed that all were within the reference ranges reported for commercially available soybeans, thereby demonstrating the substantial equivalence of these transgenic and non-transgenic seeds.

Characterization of Brassica juncea–Alternaria brassicicola interaction and jasmonic acid carboxyl methyl transferase expression

The mode of disease progression during Alternaria brassicicola infection, a prototype of necrotrophic fungal infection, was studied in mustard, Brassica juncea. During the disease advancement in mustard after infection with A. brassicicola, production of reactive oxygen species occured within 16 to 24h in B. juncea cells. Severe necrosis was observed after 2days of infection in B. juncea leaves with the development of necrotic DNA. The transcriptional activation of jasmonic acid carboxyl methyl transferase (JMT) was observed after 2days post infection with A. brassicicola. Differential expression of JMT was observed in various tissues of mustard with the detection of the protein in mustard leaves only after treatment with jasmonic acid, but always found in young buds and to a lesser extent in opened flowers. Since JMT is involved in positive feedback regulation of jasmonate pathway and the jasmonic acid responsive genes, it could be a good target for achieving resistance against necrotrophic pathogens.

Expression of a functional jasmonic acid carboxyl methyltransferase is negatively correlated with strawberry fruit development

The volatile metabolite methyl jasmonate (MeJA) plays an important role in intra- and interplant communication and is involved in diverse biological processes. In this study, we report the cloning and functional characterization of a S-adenosyl-l-methionine:jasmonic acid carboxyl methyltransferase (JMT) from Fragaria vesca and Fragaria×ananassa. Biochemical assays and comprehensive transcript analyses showed that JMT has been erroneously annotated as gene fusion with a carboxyl methyltransferase (CMT) (gene15184) in the first published genome sequence of F. vesca. Recombinant FvJMT catalyzed the formation of MeJA with KM value of 22.3μM while FvCMT and the fusion protein were almost inactive. Activity of JMT with benzoic acid and salicylic acid as substrates was less than 1.5% of that with JA. Leucine at position 245, an amino acid missing in other JMT sequences is essential for activity of FvJMT. In accordance with MeJA levels, JMT transcript levels decreased steadily during strawberry fruit ripening, as did the expression levels of JA biosynthesis and regulatory genes. It appears that CMT has originated by a recent duplication of JMT and lost its enzymatic activity toward JA. In the newest version of the strawberry genome sequence (June 2014) CMT and JMT are annotated as separate genes in accordance with differential temporal and spatial expression patterns of both genes in Fragaria sp. In conclusion, MeJA, the inactive derivative of JA, is probably involved in early steps of fruit development by modulating the levels of the active plant hormone JA.