Methanol may function as a cross-kingdom signal

Sweat-based stress screening with gas chromatography-ion mobility spectrometry and electronic nose

BACKGROUND

Diagnosis of stress generally involves uses of questionnaires which can provide biased results. The more reliable approach relies on observation of individual symptoms by psychiatrists which is time consuming and could not be applicable for massive scale screening tests. This research established alternative approaches with gas chromatography-ion mobility spectrometry (GC-IMS) and electronic nose (e-nose) to perform fast stress screening based on fingerprinting of highly volatile compounds in headspaces of sweat. The investigated samples were obtained from 154 female nurse volunteers who also provided the data of questionnaire-based mental health scores with the high stress cases confirmed by psychiatrists.

RESULTS

The interviews by psychiatrists revealed 14 volunteers with high stress. Their axillary sweat samples and that from 32 nurses with low/moderate stress (controls) were collected onto cotton rods and analysed with GC-IMS. The possible marker peaks were selected based on the accuracy data. They were tentatively identified as ammonia, diethyl ether, methanol, octane, pentane, acetone and dimethylamine which could involve different endogenous mechanisms or the relationships with the local microbiomes. The data were further analysed using partial least squares discriminant analysis with the receiver operating characteristic curves showing the optimum accuracy, sensitivity and selectivity of 87%, 86% and 88%, respectively. Providing that the samples were obtained from the nurses without deodorant uses, the high stress cases could be screened using e-nose sensors with the accuracy of 89%. The sensor responses could be correlated with the marker peak area data in GC-IMS with the coefficients ranging from -0.70 to 0.80.

SIGNIFICANCE

This represents the first investigation of highly volatile compound markers in sweat for high stress screening. The established methods were simple, reliable, rapid and non-invasive, which could be further adapted into the portable platform of e-nose sensors with the practical application to perform the screening tests for nurses in Phra Nakorn Si Ayutthaya hospital, Thailand.

Global metabolome profiling of exhaled breath condensates in male smokers with asthma COPD overlap and prediction of the disease

Asthma-chronic obstructive pulmonary disease (COPD) overlap, termed as ACO, is a complex heterogeneous disease characterised by persistent airflow limitation, which manifests features of both asthma and COPD. These patients have a worse prognosis, in terms of more frequent and severe exacerbations, more frequent symptoms, worse quality of life, increased comorbidities and a faster lung function decline. In absence of clear diagnostic or therapeutic guidelines, ACO presents as a challenge to clinicians. The present study aims to investigate whether ACO patients have a distinct exhaled breath condensate (EBC) metabolic profile in comparison to asthma and COPD. A total of 132 age and BMI matched male smokers were recruited in the exploratory phase which consisted of (i) controls = 33 (ii) asthma = 34 (iii) COPD = 30 and (iv) ACO = 35. Using nuclear magnetic resonance (NMR) metabolomics, 8 metabolites (fatty acid, propionate, isopropanol, lactate, acetone, valine, methanol and formate) were identified to be significantly dysregulated in ACO subjects when compared to both, asthma and COPD. The expression of these dysregulated metabolites were further validated in a fresh patient cohort consisting of (i) asthma = 32 (ii) COPD = 32 and (iii) ACO = 40, which exhibited a similar expression pattern. Multivariate receiver operating characteristic (ROC) curves generated using these metabolites provided a robust ACO classification model. The findings were also integrated with previously identified serum metabolites and inflammatory markers to develop a robust predictive model for differentiation of ACO. Our findings suggest that NMR metabolomics of EBC holds potential as a platform to identify robust, non-invasive biomarkers for differentiating ACO from asthma and COPD.

Biochemical Methanol Gas Sensor (MeOH Bio-Sniffer) for Non-Invasive Assessment of Intestinal Flora from Breath Methanol

Methanol (MeOH) in exhaled breath has potential for non-invasive assessment of intestinal flora. In this study, we have developed a biochemical gas sensor (bio-sniffer) for MeOH in the gas phase using fluorometry and a cascade reaction with two enzymes, alcohol oxidase (AOD) and formaldehyde dehydrogenase (FALDH). In the cascade reaction, oxidation of MeOH was initially catalyzed by AOD to produce formaldehyde, and then this formaldehyde was successively oxidized via FALDH catalysis together with reduction of oxidized form of β-nicotinamide adenine dinucleotide (NAD+). As a result of the cascade reaction, reduced form of NAD (NADH) was produced, and MeOH vapor was measured by detecting autofluorescence of NADH. In the development of the MeOH bio-sniffer, three conditions were optimized: selecting a suitable FALDH for better discrimination of MeOH from ethanol in the cascade reaction; buffer pH that maximizes the cascade reaction; and materials and methods to prevent leaking of NAD+ solution from an AOD-FALDH membrane. The dynamic range of the constructed MeOH bio-sniffer was 0.32-20 ppm, which encompassed the MeOH concentration in exhaled breath of healthy people. The measurement of exhaled breath of a healthy subject showed a similar sensorgram to the standard MeOH vapor. These results suggest that the MeOH bio-sniffer exploiting the cascade reaction will become a powerful tool for the non-invasive intestinal flora testing.

Sensitive and selective methanol biosensor using two-enzyme cascade reaction and fluorometry for non-invasive assessment of intestinal bacteria activity

For understanding the status of intestinal flora non-invasively, methanol (MeOH) has been attracting the attention. In this study, we have developed and compared two different liquid-phase methanol biosensors. One, referred to as the AOD electrosensor, utilized alcohol oxidase (AOD) and an oxygen electrode. It electrochemically measured the decrease in oxygen through AOD-catalyzed oxidation of MeOH. The other, referred to as the AOD-FALDH fluorosensor, exploited a cascade reaction of AOD and formaldehyde dehydrogenase (FALDH) in conjunction with a fiber-optic sensor. It measured increase in the fluorescence from reduced form of β-nicotinamide adenine dinucleotide (NADH) that was a final product of the two-enzyme cascade reaction. Due to the cascade reaction, the AOD-FALDH fluorosensor showed 3 times better sensitivity along with 335 times wider dynamic range (494 nM-100 mM) than those of the AOD electrosensor (1.5-300 μM). The selectivity to MeOH was also improved by the cascade reaction with AOD-FALDH as no sensor output was observed from other aliphatic alcohols than MeOH in contrast to the AOD electrosensor. Although the use of FALDH resulted in the increase in the sensor output from aldehydes, such as acetaldehyde and formaldehyde, considering their concentrations in body fluids, the influence on the sensor output is limited. These results indicate that incorporating the cascade reaction into fluorometry enables enhanced biosensing of MeOH that will be useful for assessment of intestinal flora with little burden.

The nanomolar sensing of nicotinamide adenine dinucleotide in human plasma using a cycling assay in albumin modified simulated body fluids

Nicotinamide adenine dinucleotide (NAD), a prominent member of the pyridine nucleotide family, plays a pivotal role in cell-oxidation protection, DNA repair, cell signalling and central metabolic pathways, such as beta oxidation, glycolysis and the citric acid cycle. In particular, extracellular NAD⁺ has recently been demonstrated to moderate pathogenesis of multiple systemic diseases as well as aging. Herein we present an assaying method, that serves to quantify extracellular NAD⁺ in human heparinised plasma and exhibits a sensitivity ranging from the low micromolar into the low nanomolar domain. The assay achieves the quantification of extracellular NAD⁺ by means of a two-step enzymatic cycling reaction, based on alcohol dehydrogenase. An albumin modified revised simulated body fluid was employed as standard matrix in order to optimise enzymatic activity and enhance the linear behaviour and sensitivity of the method. In addition, we evaluated assay linearity, reproducibility and confirmed long-term storage stability of extracellular NAD⁺ in frozen human heparinised plasma. In summary, our findings pose a novel standardised method suitable for high throughput screenings of extracellular NAD⁺ levels in human heparinised plasma, paving the way for new clinical discovery studies.

Human Endogenous Formaldehyde as an Anticancer Metabolite: Its Oxidation Downregulation May Be a Means of Improving Therapy

Malignant cells are characterized by an increased content of endogenous formaldehyde formed as a by-product of biosynthetic processes. Accumulation of formaldehyde in cancer cells is combined with activation of the processes of cellular formaldehyde clearance. These mechanisms include increased ALDH and suppressed ADH5/FDH activity, which oncologists consider poor and favorable prognostic markers, respectively. Here, the sources and regulation of formaldehyde metabolism in cancer cells are reviewed. The authors also analyze the participation of oncoproteins such as fibulins, FGFR1, HER2/neu, FBI-1, and MUC1-C in the control of genes related to formaldehyde metabolism, suggesting the existence of two mutually exclusive processes in cancer cells: 1) production and 2) oxidation and elimination of formaldehyde from the cell. The authors hypothesize that the study of the anticancer properties of disulfiram and alpha lipoic acid - which affect the balance of formaldehyde in the body - may serve as the basis of future anticancer therapy.

Changes in photosynthetic rate and stress volatile emissions through desiccation-rehydration cycles in desiccation-tolerant epiphytic filmy ferns (Hymenophyllaceae)

Exposure to recurrent desiccation cycles carries a risk of accumulation of reactive oxygen species that can impair leaf physiological activity upon rehydration, but changes in filmy fern stress status through desiccation and rewatering cycles have been poorly studied. We studied foliage photosynthetic rate and volatile marker compounds characterizing cell wall modifications (methanol) and stress development (lipoxygenase [LOX] pathway volatiles and methanol) through desiccation-rewatering cycles in lower-canopy species Hymenoglossum cruentum and Hymenophyllum caudiculatum, lower- to upper-canopy species Hymenophyllum plicatum and upper-canopy species Hymenophyllum dentatum sampled from a common environment and hypothesized that lower canopy species respond more strongly to desiccation and rewatering. In all species, rates of photosynthesis and LOX volatile emission decreased with progression of desiccation, but LOX emission decreased with a slower rate than photosynthesis. Rewatering first led to an emission burst of LOX volatiles followed by methanol, indicating that the oxidative burst was elicited in the symplast and further propagated to cell walls. Changes in LOX emissions were more pronounced in the upper-canopy species that had a greater photosynthetic activity and likely a greater rate of production of photooxidants. We conclude that rewatering induces the most severe stress in filmy ferns, especially in the upper canopy species.

In vitro oral processing of raw tomato: Novel insights into the role of endogenous fruit enzymes

During consumption of fruits, the breakdown of the fruit tissue due to oral processing (chewing, mixing with saliva) may activate or increase the rate of endogenous enzyme activities via the disruption of the cell wall, cellular decompartmentalization, and particle size reduction allowing the enzymes to reach their substrates. The aim of this study was to investigate the activity of one such endogenous fruit enzyme (pectin methylesterase [PME] [E.C. 3.1.1.11]) during in vitro oral processing of raw tomatoes and associated changes in viscosity and microstructure. Oral processing of tomatoes purees was examined in the presence of artificial saliva (AS) at 37°C. in vitro oral processing was followed using immunofluorescence microscopy, apparent viscosity measurements, spectrophotometric, and titrimetric techniques. The results demonstrated that PME had slight but significant activity in the tomato fruit during in vitro oral processing generating methanol as a function of oral processing time, which was further evidenced using immunolabeling techniques to detect methylated pectin epitopes. A significant shear-thinning behavior of the tomato puree was observed due to dilution and/or endogenous fruit enzyme activity. These results suggest that activity of other fruit enzymes, such as polygalacturonase, which catalyzed the depolymerization of unmethylated pectin chains, might have resulted in a decrease in viscosity, which compensated for the increased potential for gel formation (if any) caused by PME. These interesting insights into the role of endogenous fruit enzymes might pave the way to the understanding of fruit viscosity modification occurring in the mouth and help in rational design of new fruit-based products.

The Antioxidant Cofactor Alpha-Lipoic Acid May Control Endogenous Formaldehyde Metabolism in Mammals

The healthy human body contains small amounts of metabolic formaldehyde (FA) that mainly results from methanol oxidation by pectin methylesterase, which is active in a vegetable diet and in the gastrointestinal microbiome. With age, the ability to maintain a low level of FA decreases, which increases the risk of Alzheimer's disease and dementia. It has been shown that 1,2-dithiolane-3-pentanoic acid or alpha lipoic acid (ALA), a naturally occurring dithiol and antioxidant cofactor of mitochondrial α-ketoacid dehydrogenases, increases glutathione (GSH) content and FA metabolism by mitochondrial aldehyde dehydrogenase 2 (ALDH2) thus manifests a therapeutic potential beyond its antioxidant property. We suggested that ALA can contribute to a decrease in the FA content of mammals by acting on ALDH2 expression. To test this assumption, we administered ALA in mice in order to examine the effect on FA metabolism and collected blood samples for the measurement of FA. Our data revealed that ALA efficiently eliminated FA in mice. Without affecting the specific activity of FA-metabolizing enzymes (ADH1, ALDH2, and ADH5), ALA increased the GSH content in the brain and up-regulated the expression of the FA-metabolizing ALDH2 gene in the brain, particularly in the hippocampus, but did not impact its expression in the liver in vivo or in rat liver isolated from the rest of the body. After ALA administration in mice and in accordance with the increased content of brain ALDH2 mRNA, we detected increased ALDH2 activity in brain homogenates. We hypothesized that the beneficial effects of ALA on patients with Alzheimer's disease may be associated with accelerated ALDH2-mediated FA detoxification and clearance.

Control of Leaf Senescence by an MeOH-Jasmonates Cascade that Is Epigenetically Regulated by OsSRT1 in Rice

Although considerable progress has been made in identifying the genes regulating accumulation of hormones that are involved in leaf senescence, only a few studies have focused on natural variations in jasmonates content and much less on the underlying genetic basis. Moreover, the epigenetic regulation of jasmonate-mediated leaf senescence remains largely unknown. In this study, we carried out metabolic profiling of a worldwide collection of rice accessions and demonstrated that there are substantial variations in jasmonate levels among these accessions. A subsequent metabolite-based genome-wide association study identified candidates for two major quantitative genes (QTGs), OsPME1 and OsTSD2, affecting the content of jasmonates. Further investigations using a series of relevant mutants and transgenic lines revealed the MeOH-jasmonate cascade plays an important role in regulating leaf senescence. Moreover, we showed that OsSRT1, one of the two Sir2 (silent information regulator 2) homologs in rice, negatively regulates leaf senescence by repressing expression of the biosynthetic genes of this metabolic cascade and at least particially through histone H3K9 deacetylation of OsPME1. Taken together, our results indicate that the MeOH-jasmonates cascade and its epigenetic regulation are crucial for controlling leaf senescence process in rice.

Metabolism and Virulence Strategies in Dickeya-Host Interactions

Dickeya, a genus of the Enterobacteriaceae family, all cause plant diseases. They are aggressive necrotrophs that have both a wide geographic distribution and a wide host range. As a plant pathogen, Dickeya has had to adapt to a vegetarian diet. Plants constitute a large storage of carbohydrates; they contain substantial amounts of soluble sugars and the plant cell wall is composed of long polysaccharides. Metabolic functions used by Dickeya in order to multiply during infection are essential aspects of pathogenesis. Dickeya is able to catabolize a large range of oligosaccharides and glycosides of plant origin. Glucose, fructose, and sucrose are all efficiently metabolized by the bacteria. To avoid the formation of acidic products, their final catabolism involves the butanediol pathway, a nonacidifying fermentative pathway. The assimilation of plant polysaccharides necessitates their prior cleavage into oligomers. Notably, the Dickeya virulence strategy is based on its capacity to dissociate the plant cell wall and, for this, the bacteria secrete an extensive set of polysaccharide degrading enzymes, composed mostly of pectinases. Since pectic polymers have a major role in plant tissue cohesion, pectinase action results in plant rot. The pectate lyases secreted by Dickeya play a double role as virulence factors and as nutrient providers. This dual function implies that the pel gene expression is regulated by both metabolic and virulence regulators. The control of sugar assimilation by specific or global regulators enables Dickeya to link its nutritional status to virulence, a coupling that optimizes the different phases of infection.

Scaling of photosynthesis and constitutive and induced volatile emissions with severity of leaf infection by rust fungus (Melampsora larici-populina) in Populus balsamifera var. suaveolens

Fungal infections result in decreases in photosynthesis, induction of stress and signaling volatile emissions and reductions in constitutive volatile emissions, but the way different physiological processes scale with the severity of infection is poorly known. We studied the effects of infection by the obligate biotrophic fungal pathogen Melampsora larici-populina Kleb., the causal agent of poplar leaf rust disease, on photosynthetic characteristics, and constitutive isoprene and induced volatile emissions in leaves of Populus balsamifera var. suaveolens (Fisch.) Loudon. exhibiting different degrees of damage. The degree of fungal damage, quantified by the total area of chlorotic and necrotic leaf areas, varied between 0 (noninfected control) and ∼60%. The rates of all physiological processes scaled quantitatively with the degree of visual damage, but the scaling with damage severity was weaker for photosynthetic characteristics than for constitutive and induced volatile release. Over the whole range of damage severity, the net assimilation rate per area (AA) decreased 1.5-fold, dry mass per unit area 2.4-fold and constitutive isoprene emissions 5-fold, while stomatal conductance increased 1.9-fold and dark respiration rate 1.6-fold. The emissions of key stress and signaling volatiles (methanol, green leaf volatiles, monoterpenes, sesquiterpenes and methyl salicylate) were in most cases nondetectable in noninfested leaves, and increased strongly with increasing the spread of infection. The moderate reduction in AA resulted from the loss of photosynthetically active biomass, but the reduction in constitutive isoprene emissions and the increase in induced volatile emissions primarily reflected changes in the activities of corresponding biochemical pathways. Although all physiological alterations in fungal-infected leaves occurred in a stress severity-dependent manner, modifications in primary and secondary metabolic pathways scaled differently due to contrasting operational mechanisms.

Diet-induced and mono-genetic obesity alter volatile organic compound signature in mice

The prevalence of obesity is still rising in many countries, resulting in an increased risk of associated metabolic diseases. In this study we aimed to describe the volatile organic compound (VOC) patterns symptomatic for obesity. We analyzed high fat diet (HFD) induced obese and mono-genetic obese mice (global knock-in mutation in melanocortin-4 receptor MC4R-ki). The source strengths of 208 VOCs were analyzed in ad libitum fed mice and after overnight food restriction. Volatiles relevant for a random forest-based separation of obese mice were detected (26 in MC4R-ki, 22 in HFD mice). Eight volatiles were found to be important in both obesity models. Interestingly, by creating a partial correlation network of the volatile metabolites, the chemical and metabolic origins of several volatiles were identified. HFD-induced obese mice showed an elevation in the ketone body acetone and acrolein, a marker of lipid peroxidation, and several unidentified volatiles. In MC4R-ki mice, several yet-unidentified VOCs were found to be altered. Remarkably, the pheromone (methylthio)methanethiol was found to be reduced, linking metabolic dysfunction and reproduction. The signature of volatile metabolites can be instrumental in identifying and monitoring metabolic disease states, as shown in the screening of the two obese mouse models in this study. Our findings show the potential of breath gas analysis to non-invasively assess metabolic alterations for personalized diagnosis.

Metabolic methanol: molecular pathways and physiological roles

Methanol has been historically considered an exogenous product that leads only to pathological changes in the human body when consumed. However, in normal, healthy individuals, methanol and its short-lived oxidized product, formaldehyde, are naturally occurring compounds whose functions and origins have received limited attention. There are several sources of human physiological methanol. Fruits, vegetables, and alcoholic beverages are likely the main sources of exogenous methanol in the healthy human body. Metabolic methanol may occur as a result of fermentation by gut bacteria and metabolic processes involving S-adenosyl methionine. Regardless of its source, low levels of methanol in the body are maintained by physiological and metabolic clearance mechanisms. Although human blood contains small amounts of methanol and formaldehyde, the content of these molecules increases sharply after receiving even methanol-free ethanol, indicating an endogenous source of the metabolic methanol present at low levels in the blood regulated by a cluster of genes. Recent studies of the pathogenesis of neurological disorders indicate metabolic formaldehyde as a putative causative agent. The detection of increased formaldehyde content in the blood of both neurological patients and the elderly indicates the important role of genetic and biochemical mechanisms of maintaining low levels of methanol and formaldehyde.

Homogalacturonan-modifying enzymes: structure, expression, and roles in plants

Understanding the changes affecting the plant cell wall is a key element in addressing its functional role in plant growth and in the response to stress. Pectins, which are the main constituents of the primary cell wall in dicot species, play a central role in the control of cellular adhesion and thereby of the rheological properties of the wall. This is likely to be a major determinant of plant growth. How the discrete changes in pectin structure are mediated is thus a key issue in our understanding of plant development and plant responses to changes in the environment. In particular, understanding the remodelling of homogalacturonan (HG), the most abundant pectic polymer, by specific enzymes is a current challenge in addressing its fundamental role. HG, a polymer that can be methylesterified or acetylated, can be modified by HGMEs (HG-modifying enzymes) which all belong to large multigenic families in all species sequenced to date. In particular, both the degrees of substitution (methylesterification and/or acetylation) and polymerization can be controlled by specific enzymes such as pectin methylesterases (PMEs), pectin acetylesterases (PAEs), polygalacturonases (PGs), or pectate lyases-like (PLLs). Major advances in the biochemical and functional characterization of these enzymes have been made over the last 10 years. This review aims to provide a comprehensive, up to date summary of the recent data concerning the structure, regulation, and function of these fascinating enzymes in plant development and in response to biotic stresses.

Dietary methanol regulates human gene activity

Methanol (MeOH) is considered to be a poison in humans because of the alcohol dehydrogenase (ADH)-mediated conversion of MeOH to formaldehyde (FA), which is toxic. Our recent genome-wide analysis of the mouse brain demonstrated that an increase in endogenous MeOH after ADH inhibition led to a significant increase in the plasma MeOH concentration and a modification of mRNA synthesis. These findings suggest endogenous MeOH involvement in homeostasis regulation by controlling mRNA levels. Here, we demonstrate directly that study volunteers displayed increasing concentrations of MeOH and FA in their blood plasma when consuming citrus pectin, ethanol and red wine. A microarray analysis of white blood cells (WBC) from volunteers after pectin intake showed various responses for 30 significantly differentially regulated mRNAs, most of which were somehow involved in the pathogenesis of Alzheimer's disease (AD). There was also a decreased synthesis of hemoglobin mRNA, HBA and HBB, the presence of which in WBC RNA was not a result of red blood cells contamination because erythrocyte-specific marker genes were not significantly expressed. A qRT-PCR analysis of volunteer WBCs after pectin and red wine intake confirmed the complicated relationship between the plasma MeOH content and the mRNA accumulation of both genes that were previously identified, namely, GAPDH and SNX27, and genes revealed in this study, including MME, SORL1, DDIT4, HBA and HBB. We hypothesized that human plasma MeOH has an impact on the WBC mRNA levels of genes involved in cell signaling.

Endogenous methanol regulates mammalian gene activity

We recently showed that methanol emitted by wounded plants might function as a signaling molecule for plant-to-plant and plant-to-animal communications. In mammals, methanol is considered a poison because the enzyme alcohol dehydrogenase (ADH) converts methanol into toxic formaldehyde. However, the detection of methanol in the blood and exhaled air of healthy volunteers suggests that methanol may be a chemical with specific functions rather than a metabolic waste product. Using a genome-wide analysis of the mouse brain, we demonstrated that an increase in blood methanol concentration led to a change in the accumulation of mRNAs from genes primarily involved in detoxification processes and regulation of the alcohol/aldehyde dehydrogenases gene cluster. To test the role of ADH in the maintenance of low methanol concentration in the plasma, we used the specific ADH inhibitor 4-methylpyrazole (4-MP) and showed that intraperitoneal administration of 4-MP resulted in a significant increase in the plasma methanol, ethanol and formaldehyde concentrations. Removal of the intestine significantly decreased the rate of methanol addition to the plasma and suggested that the gut flora may be involved in the endogenous production of methanol. ADH in the liver was identified as the main enzyme for metabolizing methanol because an increase in the methanol and ethanol contents in the liver homogenate was observed after 4-MP administration into the portal vein. Liver mRNA quantification showed changes in the accumulation of mRNAs from genes involved in cell signalling and detoxification processes. We hypothesized that endogenous methanol acts as a regulator of homeostasis by controlling the mRNA synthesis.

Cell wall methanol as a signal in plant immunity

Cell wall pectin forms a matrix around the cellulose-xyloglucan network that is composed of rhamnogalacturonan I, rhamnogalacturonan II, and homogalacturonan (HG), a major pectic polymer consisting of α-1,4-linked galacturonic acids. HG is secreted in a highly methyl-esterified form and selectively de-methyl-esterified by pectin methylesterases (PMEs) during cell growth and pathogen attack. The mechanical damage that often precedes the penetration of the leaf by a pathogen promotes the activation of PME, which in turn leads to the emission of methanol (MeOH), an abundant volatile organic compound, which is quickly perceived by the intact leaves of the damaged plant, and the neighboring plants. The exposure to MeOH may result in a "priming" effect on intact leaves, setting the stage for the within-plant, and neighboring plant immunity. The emission of MeOH by a wounded plant enhances the resistance of the non-wounded, neighboring "receiver" plants to bacterial pathogens and promotes cell-to-cell communication that facilitates the spread of viruses in neighboring plants.