Acid Carboxyl Methyltransferase Research Articles

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.

Componentes de aroma floral em Rhododendron fortunei e sua regulação pela expressão gênica de S-adenosil-L-metionina: ácido benzóico carboxil metil transferase (BAMT)

ABSTRACT: Rhododendron fortune belongs to a scented Rhododendron species native to China, which produces fragrant flowers of great ornamental and environmental values for landscaping or indoor beautification. However, the scents in Rhododendron fortuneihave not yet been investigated, let alone the mechanism of the formation of these fragrance in the flowers. In this study, we measured the scents in terms of its volatile components and contents (VOC) in Rhododendron fortuneiat four different flowering stages and in different tissues of the plant by headspace solid-phase micro-extraction combined (HS-SPME) with gas chromatography-mass spectrometry (GC-MS). Then the characteristic aromatic values, which reflects the degree of scent perception by human, of each VOC in the plant was calculated according to its respective aromatic thresholds. Results showed that three main VOCs measured from highest to lowest are methyl benzoates, terpenes and fatty acid derivatives. Their content increased after the flower bud opening and reached the highest at half to full blossom. In a flower most VOC contents were measured in petals and only trace amount in other tissues such as stamen, pistil. A small amount of VOCs was determined in leaves as well.All aromatic values were almost corresponded to the contents of three main VOCs, indicating that the flower fragrance arises truly from these VOC components. S-adenosyl-L-methionine: benzoic acid carboxyl methyl transferase (BAMT) catalyzes the final step to form methyl benzoates. To understand the mechanism of the formation of this main type fragrance and its regulation, we firstly isolate a gene of RfBAMT from petal of Rhododendron fortuneiby using homologous cloning and RACE technology. The full length of its cDNA was 1383 bp，with an open reading frame of 1104 bp, encoding a total of 368 amino acids. The phylogenetic tree analysis showed that RfBAMT was the closest to the BSMT of Camellia japonica, belonging to methyltransferases family. Then we measured the expression level of RfBAMT again at four flower developmental stages and in different flower tissues and leaves. The results showed that the expression level of this gene was highly positively correlated with the emitted content of methyl benzoates in the flowering, implying that RfBAMT plays a pivotal role in the formation and regulation of methyl benzoates in Rhododendron fortune.Thisresearchshowed that the RfBAMT was cloned and identified in our study and its expression level was highly positively correlated with the emitted content of methyl benzoates in the flowers and leaves, which indicated this gene may play an important role on regulation of methyl benzoate synthesis in Rhododendron fortunei.

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.

High-resolution transcriptome and volatile assays provide insights into flower development and aroma formation in single- and double-petal jasmines (Jasminum sambac)

Jasmine ( Jasminum sambac ) is one of the most popular ornamental plant species in the world, with diverse floral morphology, including single-petal (SP), double-petal (DP) and multi-petal (MP). Here, based on our recently published chromosome-level genome assemblies of SP and DP Jasmines, we generated high-resolution transcriptional profiles of SP and DP jasmine flowers at six developmental stages and identified key events and regulators contributing to the differences between the two jasmines. The upregulated genes of DP jasmine in early flower development were mainly related to photosynthesis and light reactions, which may contribute to its stronger energy metabolism and environmental adaptability compared with SP jasmine. AGL63 (GOA) and PLETHORA3 (PLT3) motifs involved in floral organogenesis in Arabidopsis were overrepresented at the initial stages in SP and DP, respectively, and may be involved in the development of different petal layers in jasmines. The specific high expression of volatile terpene and benzene/phenylpropane synthesis genes during flowering is an important factor why jasmines during bud development and other tissues are scentless. This factor is also responsible for the typical floral volatiles of jasmine, including terpenes ( α -farnesene, linalool , and ( E )- β -ocimene), and benzenoid lipids (benzyl acetate, methyl salicylate , and methyl benzoate). The high content of α -farnesene and the low content of other core volatiles may constitute the fresh and elegant fragrance of SP compared to DP jasmine. Only DP jasmine had high expression of benzoic acid/salicylic acid carboxyl methyltransferase (BMST), which resulted in its higher content of volatile methyl salicylate and methyl benzoate . Our findings lay the foundation for understanding the flower development and aroma formation mechanisms of different jasmine petal morphologies. • High-resolution transcriptome and volatile assays for single- and double-petal jasmine. • Identified key events and regulators contributing to the differences between two jasmines. • Determine why jasmines were scentless during bud development and other tissues. • The high content of α-farnesene may contribute to the fresh and sweet fragrance of single-petal jasmine. • The expression of BMST was only higher in DP jasmine, resulting in higher content of methyl salicylate and methyl benzoate.

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.

Identification and characterization of regulatory pathways involved in early flowering in the new leaves of alfalfa (Medicago sativa L.) by transcriptome analysis

BackgroundAlfalfa (Medicago sativa L.) is a perennial legume extensively planted throughout the world as a high nutritive value livestock forage. Flowering time is an important agronomic trait that contributes to the production of alfalfa hay and seeds. However, the underlying molecular mechanisms of flowering time regulation in alfalfa are not well understood.ResultsIn this study, an early-flowering alfalfa genotype 80 and a late-flowering alfalfa genotype 195 were characterized for the flowering phenotype. Our analysis revealed that the lower jasmonate (JA) content in new leaves and the downregulation of JA biosynthetic genes (i.e. lipoxygenase, the 12-oxophytodienoate reductase-like protein, and salicylic acid carboxyl methyltransferase) may play essential roles in the early-flowering phenotype of genotype 80. Further research indicated that genes encode pathogenesis-related proteins [e.g. leucine rich repeat (LRR) family proteins, receptor-like proteins, and toll-interleukin-like receptor (TIR)-nucleotide-binding site (NBS)-LRR class proteins] and members of the signaling receptor kinase family [LRR proteins, kinases domain of unknown function 26 (DUF26) and wheat leucine-rich repeat receptor-like kinase10 (LRK10)-like kinases] are related to early flowering in alfalfa. Additionally, those involved in secondary metabolism (2-oxoglutarate/Fe (II)-dependent dioxygenases and UDP-glycosyltransferase) and the proteasome degradation pathway [really interesting new gene (RING)/U-box superfamily proteins and F-box family proteins] are also related to early flowering in alfalfa.ConclusionsIntegrated phenotypical, physiological, and transcriptomic analyses demonstrate that hormone biosynthesis and signaling pathways, pathogenesis-related genes, signaling receptor kinase family genes, secondary metabolism genes, and proteasome degradation pathway genes are responsible for the early flowering phenotype in alfalfa. This will provide new insights into future studies of flowering time in alfalfa and inform genetic improvement strategies for optimizing this important trait.

Overexpression of Citrus reticulata SAMT in Nicotiana tabacum increases MeSA volatilization and decreases Xylella fastidiosa symptoms.

Nicotiana tabacum overexpressing CrSAMT from Citrus reticulata increased production of MeSA, which works as an airborne signal in neighboring wild-type plants, inducing PR1 and increasing resistance to the pathogen Xylella fastidiosa. Xylella fastidiosa is one of the major threats to plant health worldwide, affecting yield in many crops. Despite many efforts, the development of highly productive resistant varieties has been challenging. In studying host plant resistance, the S-adenosyl-L-methionine: salicylic acid carboxyl methyltransferase gene (SAMT) from Citrus reticulata, a X. fastidiosa resistant species, was upregulated in response to pathogen infection. SAMT is involved with the catalysis and production of methyl salicylate (MeSA), an airborne signal responsible for triggering systemic acquired resistance. Here we used tobacco as a model system and generated transgenic plants overexpressing C. reticulata SAMT (CrSAMT). We performed an in silico structural characterization of CrSAMT and investigated its biotechnological potential in modulating the immune system in transgenic plants. The increase of MeSA production in transgenic lines was confirmed by gas chromatography (GC-MS). The transgenic lines showed upregulation of PR1, and their incubation with neighboring wild-type plants activated PR1 expression, indicating that MeSA worked as an airborne signal. In addition, transgenic plants showed significantly fewer symptoms when challenged with X. fastidiosa. Altogether, these data suggest that CrSAMT plays a role in host defense response and can be used in biotechnology approaches to confer resistance against X. fastidiosa.

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.

Chromosome-scale genome assembly of sweet cherry (Prunus avium L.) cv. Tieton obtained using long-read and Hi-C sequencing

Sweet cherry (Prunus avium) is an economically significant fruit species in the genus Prunus. However, in contrast to other important fruit trees in this genus, only one draft genome assembly is available for sweet cherry, which was assembled using only Illumina short-read sequences. The incompleteness and low quality of the current sweet cherry draft genome limit its use in genetic and genomic studies. A high-quality chromosome-scale sweet cherry reference genome assembly is therefore needed. A total of 65.05 Gb of Oxford Nanopore long reads and 46.24 Gb of Illumina short reads were generated, representing ~190x and 136x coverage, respectively, of the sweet cherry genome. The final de novo assembly resulted in a phased haplotype assembly of 344.29 Mb with a contig N50 of 3.25 Mb. Hi-C scaffolding of the genome resulted in eight pseudochromosomes containing 99.59% of the bases in the assembled genome. Genome annotation revealed that more than half of the genome (59.40%) was composed of repetitive sequences, and 40,338 protein-coding genes were predicted, 75.40% of which were functionally annotated. With the chromosome-scale assembly, we revealed that gene duplication events contributed to the expansion of gene families for salicylic acid/jasmonic acid carboxyl methyltransferase and ankyrin repeat-containing proteins in the genome of sweet cherry. Four auxin-responsive genes (two GH3s and two SAURs) were induced in the late stage of fruit development, indicating that auxin is crucial for the sweet cherry ripening process. In addition, 772 resistance genes were identified and functionally predicted in the sweet cherry genome. The high-quality genome assembly of sweet cherry obtained in this study will provide valuable genomic resources for sweet cherry improvement and molecular breeding.

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.

Iodine biofortification through expression of HMT, SAMT and S3H genes in Solanum lycopersicum L.

The uptake process and physiological reaction of plants to aromatic iodine compounds have not yet been documented. The aim of this research was to compare uptake by tomato plants of KI and KIO3, as well as of organic iodine compounds – 5-ISA (5-iodosalicylic acid), 3,5-diISA (3,5-diiodosalicylic acid), 2-IBeA (2-iodobenzoic acid), 4-IBeA (4-iodobenzoic acid) and 2,3,5-triIBeA (2,3,5-triiodobenzoic acid). Only 2,3,5-triIBeA had a negative influence on plant development. All organic iodine compounds were taken up by roots and transported to leaves and fruits. Among all the compounds applied, the most efficiently transferred iodine was 2-IBeA – to fruits, and 4-IBeA – to leaves. The order of iodine accumulation in fruit cell compartments was as follows: organelles > cell walls > soluble portions of cells; for leaf and root cells, it was: organelles > cell walls or soluble portions, depending on the compound applied. The compounds studied influence iodine metabolism through expression of the HMT gene which encodes halide ion methyltransferase in leaves and roots. Also, their influence on modification of the activity of the SAMT and S3H genes that encode salicylic acid carboxyl methyltransferase and salicylic acid 3-hydroxylase was established. It was discovered that exogenously applied 5-ISA, 3,5-diISA, 2-IBeA and 4-IBeA are genuinely (endogenously) synthesised in tomato plants; to date, this has not been described for the tomato, nor for any other species of higher plant.

A salicylic acid carboxyl methyltransferase-like gene LcSAMT from Lycium chinense, negatively regulates the drought response in transgenic tobacco

Drought is the main environmental factor which limits growth, photosynthesis and yield of agricultural crops worldwide. Salicylic acid (SA) is a phenolic compound involved in plant growth and development. Salicylic acid carboxyl methyltransferase (SAMT) can catalyze the methylation of SA with S-adenosyl-L-methionine as the methyl donor to form methyl salicylate (MeSA). However, the relations between SAMT and drought tolerance in plants are largely unknown. In this study, a SAMT gene, LcSAMT, was isolated from Lycium chinense and characterized. Escherichia coli expressed LcSAMT was found to function as salicylic acid methyltransferase using in vitro enzyme assays. The expression of LcSAMT gene was observed to be elevated in L. chinense under drought stress treatment. The overexpression of LcSAMT gene markedly enhanced the MeSA content and reduced the accumulation of SA in the transgenic tobacco plants. The conversion of MeSA from SA led to the depletion of the free SA pool. The overexpression of LcSAMT gene in tobacco significantly increased sensitivity of transgenic plant to drought stress, as measured by morphological and physiological factors such as leaf photosynthetic rate and chlorophyll content, which might be due to the decreased SA accumulation. The increased accumulation of ROS, elevated MDA levels, reduced proline contents and lowered expression of APX, CAT and SOD genes were also observed in the LcSAMT transgenic tobacco plants under drought stress, which means that the LcSAMT-overexpressing transgenic tobacco plants had decreased resistance to oxidative stress in comparison with control plants under drought stress. These results thus suggested that LcSAMT responded to drought stress might through the regulation of ROS accumulation in plants. Furthermore, LcSAMT-overexpressing transgenic tobacco plants displayed decreased ABA accumulation and reduced transcript expression of NtNCED1 and NtRD22 genes. Therefore, the increased sensitivity of transgenic plants overexpressing LcSAMT gene to drought stress might also through an ABA-dependent pathway.

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.

Production of methylparaben in Escherichia coli.

Since the 1930s, parabens have been employed widely as preservatives in food, pharmaceutical, and personal care products. These alkyl esters of benzoic acid occur naturally in a broad range of plant species, where they are thought to enhance overall fitness through disease resistance and allelopathy. Current manufacture of parabens relies on chemical synthesis and theprocessing of 4-hydroxybenzoate as aprecursor. A variety of bio-based production platforms have targeted 4-hydroxybenzoate for a greener alternative to chemical manufacturing, but parabens have yet to be made in microbes. Here, we deploy the plant enzyme benzoic acid carboxyl methyltransferase together with four additional recombinant enzymes to produce methylparaben in Escherichia coli. The feasibility of a tyrosine-dependent route to methylparaben is explored, establishing a framework for linking paraben production to emerging high-tyrosine E. coli strains. However, our use of a unique plant enzyme for bio-based methylparaben biosynthesis is potentially applicable to any microbial system engineered for the manufacture of 4-hydroxybenzoate.

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.

Induced Systemic Resistance Against Citrus Canker Disease by Rhizobacteria

Citrus canker, caused by Xanthomonas citri subsp. citri, is an important citrus disease that causes significant economic losses worldwide. All commercial citrus varieties are susceptible to citrus canker. Currently, chemical control with copper based products is the main approach to control X. citri subsp. citri dispersal and plant colonization. However, extensive use of copper compounds can result in copper-resistant strains and cause adverse effects on the environment. Alternatives to chemical control involve the activation of citrus immunity to control the disease. Here, we investigated the ability of multiple rhizobacteria to induce a systemic defense response in cultivar Duncan grapefruit. Burkholderia territorii strain A63, Burkholderia metallica strain A53, and Pseudomonas geniculata strain 95 were found to effectively activate plant defense and significantly reduce symptom development in leaves challenged with X. citri subsp. citri. In the priming phase, root application of P. geniculata induced the expression of salicylic acid (SA)-signaling pathway marker genes (PR1, PR2, PR5, and salicylic acid carboxyl methyltransferase [SAM-SACM]). Gene expression analyses after X. citri subsp. citri challenge showed that root inoculation with P. geniculata strain 95 increased the relative levels of phenylalanine ammonia lyase 1 and SAM-SACM, two genes involved in the phenylpropanoid pathway as well as the biosynthesis of SA and methyl salicylate (MeSA), respectively. However, hormone analyses by UPLC-MS/MS showed no significant difference between SA in P. geniculata-treated plants and control plants at 8 days post-beneficial bacteria root inoculation. Moreover, P. geniculata root-treated plants contained higher reactive oxygen species levels in aerial tissues than control plants 8 days post-treatment application. This study demonstrates that rhizobacteria can modulate citrus immunity resulting in a systemic defense response against X. citri subsp. citri under greenhouse conditions.