Biosynthesis Of Volatile Organic Compounds Research Articles

Volatomics-Assisted Characterization of Flavor Contributors During Ripening of Wallace Melon (Cucumis melo L.)

Background:: Wallace melon has a powerful, pleasant aroma when ripe. However, little is understood about the aroma profile and the Volatile Organic Compounds (VOCs) biosynthesis during ripening. Objective:: The aim of this study is to investigate the metabolome and transcriptome of Wallace melon to study the mechanism underlying its aroma formation systematically. Methods:: HS-SPME/GC-MS and RNA-Seq were used to analyze the VOCs and associated genes of Wallace melon from three developmental stages (i.e., green, transition, and yellow stages). Results:: The aroma profiles included 47 VOCs, which were in connection with 35 genes. Yellow- stage fruits are more aromatic than the melons in the transition and green stages, producing higher concentrations of total VOCs (2994.36 ng/g), with ethyl acetate (543.16 ng/g) being the most abundant compound. Transcriptomic analysis revealed that the biosynthesis of VOCs was mainly related to fatty acid and amino acid metabolisms. Moreover, the lipoxygenase-1 (MELO3C014482.2), alcohol dehydrogenase-2 (MELO3C017100.2), 3-ketoacyl-CoA synthase-3 (MELO3C010941.2), and hydroperoxide dehydratase (MELO3C018412.2) genes were closely related to alcohols/esters through correlation analysis. Conclusion:: The information generated will deepen the understanding of Wallace melon storage quality and guide melon product development.

Berry secondary metabolites and leaf physiological parameters are independently regulated by exogenous methyl jasmonate application in Sangiovese grapevines (Vitis vinifera L.)

The role of jasmonates as elicitor of secondary metabolites is well known, and many experiments have been conducted in grapevine to evaluate their effects on berry and wine quality. Even though most of these studies used foliar jasmonates applications, little investigations have been done to assess the effects on leaves which, in turn, may indirectly affect grape metabolism potentially involving a long distance signaling or crosstalk. In this experiment we jointly investigated the specific effect of jasmonates on grape berry secondary metabolites and leaf physiological parameters to better comprehend their elicitation mechanisms in grapevine. A 10 mM methyl jasmonate (MeJA) solution was applied during the lag-phase only on the leaves or only on the clusters and compared to an untreated control. The MeJA specifically affected leaf physiological parameters and berry metabolism in the treated area. When applied only on the leaves, gas exchange parameters and leaf efficiency were reduced, stimulating the senescence mechanisms, without affecting berry metabolism. On the contrary, MeJA applied on the clusters significantly delayed berry ripening, leading to hypothesize a re-route of the berry carbon resources through the biosynthesis of volatile organic compounds which were strongly increased, especially the monoterpenes in their glycosylated form.

THE IMPACT OF STILLAGE FILTRATE ON THE SYNTHESIS OF VOLATILE IMPURITIES OF ALCOHOL AND THE OPTIMIZATION OF THE RECTIFICATION PROCESS

The aim of this research is to determine the influence stillage filtrate on the synthesis of volatile impurities in alcohol, with subsequent removal through the rectification process in a rectification unit operating in an energy-saving mode at pressures lower than atmospheric. The study was conducted at the state enterprise (hereinafter - SE) "Kozlivsky Distillery" located at: Ternopil region, Kozlivsky district, urban-type settlement Kozliv, using gas chromatographic method for determining the content of microcomponents (acetaldehyde, methanol, fusel oil components, esters) using capillary columns. The rectification unit includes various components such as the mash column, hydroselection column, rectification column, methanol column, impurity concentration column and "zero" column. During the research, technological parameters of operation of each unit component were studied, and the concentration of organic impurities in alcohol at different stages was determined. The results of this study allow improving the efficiency of the rectification unit, which is of great importance in alcohol production. Research was conducted on the impact stillage filtrate on the synthesis of volatile impurities in alcohol during fermentation. The research was carried out with the full use iltrate of stillage at the stage of preparing the fermenting substrate. The mash had different concentrations of dry substances. The stillage filtrate was obtained by centrifugation of native stillage and its suspended matter concentration did not exceed 1%. The influence of the amount stillage filtrate and the number of cycles of its recirculation on the biosynthesis of volatile organic compounds during fermentation was studied. The research results showed that the use stillage filtrate at the stage of preparing the fermenting substrate contributes to reducing water consumption and slows down the synthesis of acetaldehyde and higher alcohols during fermentation. With repeated use stillage filtrate, the synthesis process changes, which affects the concentration of volatile organic compounds in the fermentation mash. This impact should be taken into account when selecting operating modes of the rectification unit. Therefore, to obtain high-quality rectified alcohol, it is necessary to adjust the appropriate operating mode of the rectification unit and consider the influence stillage filtrate on the fermentation process.

The novel nematicide chiricanine A suppresses Bursaphelenchus xylophilus pathogenicity in Pinus massoniana by inhibiting Aspergillus and its secondary metabolite, sterigmatocystin.

Pine wilt disease (PWD) is responsible for extensive economic and ecological damage to Pinus spp. forests and plantations worldwide. PWD is caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus) and transmitted into pine trees by a vector insect, the Japanese pine sawyer (JPS, Monochamus alternatus). Host infection by PWN will attract JPS to spawn, which leads to the co-existence of PWN and JPS within the host tree, an essential precondition for PWD outbreaks. Through the action of their metabolites, microbes can manipulate the co-existence of PWN and JPS, but our understanding on how key microorganisms engage in this process remains limited, which severely hinders the exploration and utilization of promising microbial resources in the prevention and control of PWD. In this study we investigated how the PWN-associated fungus Aspergillus promotes the co-existence of PWN and JPS in the host trees (Pinus massoniana) via its secondary metabolite, sterigmatocystin (ST), by taking a multi-omics approach (phenomics, transcriptomics, microbiome, and metabolomics). We found that Aspergillus was able to promote PWN invasion and pathogenicity by increasing ST biosynthesis in the host plant, mainly by suppressing the accumulation of ROS (reactive oxygen species) in plant tissues that could counter PWN. Further, ST accumulation triggered the biosynthesis of VOC (volatile organic compounds) that attracts JPS and drives the coexistence of PWN and JPS in the host plant, thereby encouraging the local transmission of PWD. Meanwhile, we show that application of an Aspergillus inhibitor (chiricanine A treatment) results in the absence of Aspergillus and decreases the in vivo ST amount, thereby sharply restricting the PWN development in host. This further proved that Aspergillus is vital and sufficient for promoting PWD transmission. Altogether, these results document, for the first time, how the function of Aspergillus and its metabolite ST is involved in the entire PWD transmission chain, in addition to providing a novel and long-term effective nematicide for better PWD control in the field.

Transcriptome and metabolome analysis reveals stage-specific metabolite accumulation during maturity of Chinese black truffle Tuber indicum

Tuber indicum is the most economically important member of Tuber, with the highest production and widest distribution in China. However, the overexploitation of immature ascocarps not only has driven wild resources of the species toward extinction, but also has caused enconomic losses and a decline in the reputation of T.indicum quality. In this study, stage-specific metabolites of T. indicum in relation to nutritional quality and the mechanism of their accumulations were explored by transcriptome and metabolome analysis at five harvest times, representing four maturation stages. A total of 663 compounds were identified in T. indicum ascocarps by a widely targeted metabolomic approach. Lipid compounds are the most prominent metabolites (18%) in our samples and also are higher accumulation at the immature stage than at mature stage, representing 30.16% differential accumulated metabolites in this stage. Levels of some of the amino acids, such as S-(methyl) glutathione, S-adenosylmethionine, which are known truffle aroma precursors, were increased at the mature stage. The gene expression level related to the biosynthesis of volatile organic compounds were verified by qPCR. This study contributes to the preliminary understanding of metabolites variations in T. indicum ascocarps during maturity for quality evaluation and truffle biology.

Do Abiotic Stresses Affect the Aroma of Damask Roses?

Roses are popular ornamental plants all over the world. Rosa damascena Mill., also known as the damask rose, is a well-known scented rose species cultivated to produce essential oil. The essential oils obtained are high in volatile organic compounds (VOCs), which are in demand across the pharmaceutical, food, perfume, and cosmetic industries. Citronellol, nonadecane, heneicosane, caryophyllene, geraniol, nerol, linalool, and phenyl ethyl acetate are the most important components of the rose essential oil. Abiotic factors, including as environmental stress and stress generated by agricultural practises, frequently exert a selective impact on particular floral characteristics, hence influencing the overall quality and quantity of rose products. Additionally, it has been observed that the existence of stress exerts a notable impact on the chemical composition and abundance of aromatic compounds present in roses. Therefore, understanding the factors that affect the biosynthesis of VOCs, especially those representing the aroma and scent of rose, as a response to abiotic stress is important. This review provides comprehensive information on plant taxonomy, an overview of the volatolomics involving aromatic profiles, and describes the influence of abiotic stresses on the biosynthesis of the VOCs in damask rose.

Drought re-routes soil microbial carbon metabolism towards emission of volatile metabolites in an artificial tropical rainforest

Drought impacts on microbial activity can alter soil carbon fate and lead to the loss of stored carbon to the atmosphere as CO2 and volatile organic compounds (VOCs). Here we examined drought impacts on carbon allocation by soil microbes in the Biosphere 2 artificial tropical rainforest by tracking 13C from position-specific 13C-pyruvate into CO2 and VOCs in parallel with multi-omics. During drought, efflux of 13C-enriched acetate, acetone and C4H6O2 (diacetyl) increased. These changes represent increased production and buildup of intermediate metabolites driven by decreased carbon cycling efficiency. Simultaneously,13C-CO2 efflux decreased, driven by a decrease in microbial activity. However, the microbial carbon allocation to energy gain relative to biosynthesis was unchanged, signifying maintained energy demand for biosynthesis of VOCs and other drought-stress-induced pathways. Overall, while carbon loss to the atmosphere via CO2 decreased during drought, carbon loss via efflux of VOCs increased, indicating microbially induced shifts in soil carbon fate.

Volatilom und Transkriptom des Speisepilzes Agrocybe aegerita

Mushrooms are part of the human diet since time immemorial, appreciated for their nutritional value and especially for their delicious flavors. Hundreds of volatile organic compounds (VOCs) have been identified in fungi contributing to the unique aroma of each species. Generally, studies on mushroom VOCs are carried out with chopped fruiting bodies of more or less one developmental stage. For determine fungal aromas for assessment of the food quality this procedure might be adequate. Nonetheless, for analysis of the biological role of fungal VOCs in context of inter alia VOC biosynthesis or fungal communication this approach can suffer from drawbacks. First of all, damaging fruiting bodies can lead to VOC artefacts due to cell disruption and the occurrence of unnatural enzymatic reactions. Furthermore, fungal VOC profiles are dynamic, changing with ongoing development. For better understanding of the biological function of fungal VOCs it is therefore helpful to know which volatile patterns are characteristic for a certain developmental stage.Against this background, an approach was developed enabling on one hand the cultivation of fungi during different developmental stages, including the growth of fruiting bodies, and on the other hand the non‐invasive analysis of VOCs in the headspace (HS) of fungal cultures. These requirements were complied with modified crystallizing dishes for culture purposes and a HS‐ SPME‐GC‐MS approach to analyze the VOCs. This method was applied to analyze the volatilomes of the dikaryotic strain C. aegerita AAE‐3 and four monokaryotic offspring siblings with different fruiting phenotypes throughout ten life stages. At early stages, in the HS of all tested strains alcohols and ketones, such as oct‐1‐en‐3‐ol, 2‐methylbutan‐1‐ol and cyclopentanone, were the most prominent VOCs. Particularly counting for the dikaryon, the volatilome altered with continued fruiting body development exhibiting remarkable changes during sporulation. Here, sesquiterpenes, especially Δ6‐protoilludene, α‐cubebene and δ‐cadinene, were the most abundant VOCs in the HS of C. aegerita AAE‐3. After sporulation, the amount of sesquiterpenes decreased along with the appearance of other VOCs including octan‐3‐one. In contrast, less VOCs were present in the HS of the monokaryotic strains of which all were as well detectable in the HS of the dikaryon. The changes of the volatilome were the fundament for a subsequent transcriptome analysis aiming to identify enzymes involved in fungal VOC biosynthesis, especially regarding C8 VOC formation, which is, despite the fact that these substances are ubiquitous found in fungi, still barely understood. The transcriptomic study was carried out with seven developmental stages of C. aegerita AAE‐3, which during the volatilome study exhibited interesting volatile patterns. Additionally, fruiting bodies (five stages) and mycelia (seven stages) samples were harvested separately to get further insights about the putative origin of the VOCs observed in the HS of C. aegerita. Combining transcriptome and volatilome data, enzymes putatively involved in the biosynthesis of C8 oxylipins in C. aegerita including lipoxygenases (LOXs), dioxygenases (DOXs), hydroperoxide lyases (HPLs), alcohol dehydrogenases (ADHs) and ene‐ reductases could be identified. Especially the putative DOX AAE3_13098, the putative HPLs AAE3_05330 and AAE3_09203, the putative ADHs AAE3_00054 and AAE3_06559 as well as the putative ene‐reductase AAE3_15349 exhibit remarkable transcriptomic patterns making these enzymes highly interesting for future characterization studies. Furthermore, the study showed that the mycelium is probably the main source for sesquiterpenes observed during sporulation in the HS of C. aegerita AAE‐3 cultures whereas changes in the Cs profile detected in late stages of development are probably due to the activity of enzymes located in the fruiting bodies.

Grapevine genome analysis demonstrates the role of gene copy number variation in the formation of monoterpenes.

Volatile organic compounds such as terpenes influence the quality parameters of grapevine through their contribution to the flavour and aroma profile of berries. Biosynthesis of volatile organic compounds in grapevine is relatively complex and controlled by multiple genes, the majority of which are unknown or uncharacterised. To identify the genomic regions that associate with modulation of these compounds in grapevine berries, volatile metabolic data generated via GC-MS from a grapevine mapping population was used to identify quantitative trait loci (QTLs). Several significant QTLs were associated with terpenes, and candidate genes were proposed for sesquiterpene and monoterpene biosynthesis. For monoterpenes, loci on chromosomes 12 and 13 were shown to be associated with geraniol and cyclic monoterpene accumulation, respectively. The locus on chromosome 12 was shown to contain a geraniol synthase gene (VvGer), while the locus on chromosome 13 contained an α-terpineol synthase gene (VvTer). Molecular and genomic investigation of VvGer and VvTer revealed that these genes were found in tandemly duplicated clusters, displaying high levels of hemizygosity. Gene copy number analysis further showed that not only did VvTer and VvGer copy numbers vary within the mapping population, but also across recently sequenced Vitis cultivars. Significantly, VvTer copy number correlated with both VvTer gene expression and cyclic monoterpene accumulation in the mapping population. A hypothesis for a hyper-functional VvTer allele linked to increased gene copy number in the mapping population is presented and can potentially lead to selection of cultivars with modulated terpene profiles. The study highlights the impact of VvTPS gene duplication and copy number variation on terpene accumulation in grapevine.

Characterization of volatile organic compounds in grafted tomato plants upon potyvirus necrotic infection

A headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS) method was used to study the volatile organic compounds (VOCs) associated with the differential immune response of tomato plants infected with the recombinant strain of potato virus Y (PVYC-to), necrogenic to tomato. Analysis was carried out in UC82 (UC), a virus susceptible tomato variety, comparing the same UC plants grafted or not onto a virus tolerant tomato ecotype, Manduria (Ma); the three types of samples used for the GC-MS analysis were mock-inoculated UC/Ma plants, UC/Ma+PVYC-to and UC+PVYC-to plants; the VOCs obtained were 111. Results from symptomatic PVYC-to-infected UC plants showed a VOCs composition enriched in alcohols, fatty acid derivates, benzenoids, and salicylic acid derivatives, while in mock-inoculated UC/Ma plants VOCs were mainly characterized by methyl ester compounds. The VOC profile was in line with RNAseq data analyses, denoting that PVYC-to viral RNA accumulation and disease symptoms induce the specific transcriptional activation of genes involved in VOCs biosynthesis. Furthermore, principal component analysis highlighted that VOCs of PVYC-to-infected and mock-inoculated grafted plants were much closer each other than that of symptomatic PVYC-to-infected non-grafted UC plants. These results suggest that VOCs profiles of tomato plants are related to the viral RNA accumulation, disease intensity and graft-derived tolerance to PVYC-to infection.

Aroma Volatiles in Litchi Fruit: A Mini-Review

Aroma is considered a fundamental component of fruit flavor. Variations in the composition and content of volatile organic compounds (VOCs) contribute to noticeable differences in fruit aromas. Litchi is a delicious tropical and subtropical fruit, and a large number of germplasm resources with unique aromas have emerged during the past 2000 years of cultivation. In this review, our aim is to collect, compare, integrate, and summarize the available literature on the profiles of VOCs of 25 litchi cultivars. We showed that a total of 556 VOCs were reported from litchi fruit, and the aroma of litchi is mainly determined from the content and composition of monoterpenoids and alcohols, including linalool, geraniol, limonene, terpinolene, β-citronellol, p-cymene, nerol, α-terpineol, cis-rose oxide, β-myrcene, 4-terpineol, citral, and neral (cis-citral), which might contribute to the rose-like or citrus-like aroma of litchi fruit. Moreover, sulfur-containing volatile compounds (VSCs) possibly impart a special flavor to litchi fruit. This review would be a valuable resource for researchers aiming to improve litchi aroma quality by elucidating the possible mechanisms underlying VOC biosynthesis and their metabolism in litchi fruit.

Heat production and volatile biosynthesis are linked via alternative respiration in Magnolia denudata during floral thermogenesis.

Floral thermogenesis is coupled with odor emission in known thermogenic plants. It is widely accepted that elevation in floral temperature can help release of volatile organic compounds (VOCs). However, no information is available about whether floral thermogenesis is associated with VOC biosynthesis. Here, we used RNA-Sequencing (RNA-Seq) to draw a gene expression atlas of floral thermogenesis in Magnolia denudata and captured an upregulation of Alternative Oxidase (AOX) during floral thermogenesis. Western blot analyses also suggested upregulation of AOX during floral thermogenesis. Moreover, oxygen consumption analyses revealed increased activity of the AOX respiration pathway during floral thermogenesis. Using HPLC analyses, we further found that increased AOX respiration substantially promoted production of citric acid by 1.35 folds, which provided fundamental metabolite skeletons for biosynthesis of VOCs. RNA-Seq also showed upregulation of genes regulating lignin catabolism, which was in agreement with in situ Raman chemical imaging of lignin. Taken together, our results suggest the central role of AOX by coupling heat production and VOC biosynthesis in floral thermogenesis of M. denudata.

Shifts in the Bacterial Community Related to Quality Properties of Vacuum-Packaged Peeled Potatoes during Storage.

To reveal the potential relationship between the bacterial community and quality attributes of vacuum-packaged peeled potatoes, the bacterial community dynamics, visual quality, organic acids, flavor and volatile organic compounds (VOCs) during 12 days of storage under 10 °C were studied, and a correlation analysis was performed between the bacterial community and VOCs. During the whole storage, the dominant bacteria changed from Ralstonia, Pseudomonas, Pantoea and Comamonas to Clostridia, Clostridium, Lacrimispora, Lactococcus and Leuconostoc. The visual quality and hardness deteriorated significantly on day 12; meanwhile, lactic and acetic acid content accumulated to 0.79 and 4.87 mg/g FW, respectively. Potatoes’ flavor deteriorated severely after 8 days, as evidenced by results of an electronic nose (e-nose). A total of 37 VOCs were detected, and the total content showed an increasing trend from 2164.85 to 10658.68 μg/kg during the whole storage. A correlation analysis showed that Enterobacteriaceae, Erwinia, Lacrimispora, Lactococcus, Serratia, Pantoea, Clostridium, Flavobacterium and Clostridia were positively correlated with the biosynthesis of VOCs. In addition, 10 spoilage markers were screened according to a variable importance in projection (VIP) ≥ 1. Ethanol, which was the most abundant spoilage marker, was significantly related to Enterobacteriaceae, Erwinia, Lacrimispora and Lactococcus. The results of this study have great practical significance for prolonging the shelf life of fresh-cut agricultural produce.

Characterization of the aromatic profile of purple passion fruit (Passiflora edulis Sims) during ripening by HS-SPME-GC/MS and RNA sequencing

Passion fruit is a tropical liana of the Passiflora family that is commonly consumed throughout the world due to its attractive aroma and flavor. However, very limited information is available on the mechanism of aroma formation and composition of the passion fruit during ripening. Therefore, HS-SPME-GC/MS combined with transcriptome analysis was used to study the mechanism of aroma formation during passion fruit ripening. The profile analyzed included 148 volatile organic compounds (VOCs) and related differentially expressed genes (DEGs). Compared with SA, 85 VOCs and related DEGs were identified as significantly upregulated at the SB and SC stages, including esters, alcohols, ketones, hydrocarbons, alkanes, and aldehydes. Two main pathways, ester and amino acid metabolism, and related genes were analyzed with VOC biosynthesis in passion fruit. This study is the first analysis of passion fruit VOC formation and provides new insights into the flavor mechanism and quality breeding of passion fruit.

Genetic dissection of aroma biosynthesis in melon and its relationship with climacteric ripening

Aroma is an essential trait in melon fruit quality, but its complexity and genetic basis are still poorly understood. The aim of this study was the identification of quantitative trait loci (QTLs) underlying volatile organic compounds (VOCs) biosynthesis in melon rind and flesh, using a Recombinant Inbred Line (RIL) population from the cross ‘Piel de Sapo’ (PS) × ‘Védrantais’ (VED), two commercial varieties segregating for ripening behavior. A total of 82 VOCs were detected by gas chromatography–mass spectrometry (GC–MS), and 166 QTLs were identified. The main QTL cluster was on chromosome 8, collocating with the previously described ripening-related QTL ETHQV8.1, with an important role in VOCs biosynthesis. QTL clusters involved in esters, lipid-derived volatiles and apocarotenoids were also identified, and candidate genes have been proposed for ethyl 3-(methylthio)propanoate and benzaldehyde biosynthesis. Our results provide genetic insights for deciphering fruit aroma in melon and offer new tools for flavor breeding.

Aroma profile of two commercial truffle species from Yunnan and Sichuan, China: inter- and intraspecific variability and shared key compounds

Aroma is central to the worldwide success of truffles as gourmet food and the high prices paid for these edible mushrooms. In this study, volatile organic compounds (VOCs) from fruiting bodies of two Chinese truffles of commercial relevance, Tuber indicum and Tuber pseudohimalayense, were analyzed using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). We aimed to characterize the aroma profile and determine whether it would be influenced by provenance and stage of maturation. We thus collected and analyzed young, middle mature and mature fruiting bodies of each species from different locations in Yunnan and Sichuan provinces, located in southwestern China. Overall, 76 VOCs were identified, belonging to different chemical classes, i.e. alcohols and phenols, aldehydes and ketones, benzenes and methoxy compounds, hydrocarbons and amines. A large number of volatiles identified in T. indicum and T. pseudohimalayense are reported here for the first time for these truffles. While more than 50% of identified VOCs were produced by both truffle species, considerable differences were present in the aroma profiles of fruiting bodies collected at various maturation stages, revealing a dynamic pattern in the biosynthesis of VOCs. Furthermore, truffles of different provenance had distinct proportions of volatile constituents, suggesting that, besides genetic factors, edaphic and microclimatic conditions influence the synthesis of VOCs in a complex manner.

Dynamic histone acetylation in floral volatile synthesis and emission in petunia flowers.

Biosynthesis of secondary metabolites relies on primary metabolic pathways to provide precursors, energy, and cofactors, thus requiring coordinated regulation of primary and secondary metabolic networks. However, to date, it remains largely unknown how this coordination is achieved. Using Petunia hybrida flowers, which emit high levels of phenylpropanoid/benzenoid volatile organic compounds (VOCs), we uncovered genome-wide dynamic deposition of histone H3 lysine 9 acetylation (H3K9ac) during anthesis as an underlying mechanism to coordinate primary and secondary metabolic networks. The observed epigenome reprogramming is accompanied by transcriptional activation at gene loci involved in primary metabolic pathways that provide precursor phenylalanine, as well as secondary metabolic pathways to produce volatile compounds. We also observed transcriptional repression among genes involved in alternative phenylpropanoid branches that compete for metabolic precursors. We show that GNAT family histone acetyltransferase(s) (HATs) are required for the expression of genes involved in VOC biosynthesis and emission, by using chemical inhibitors of HATs, and by knocking down a specific HAT gene, ELP3, through transient RNAi. Together, our study supports that regulatory mechanisms at chromatin level may play an essential role in activating primary and secondary metabolic pathways to regulate VOC synthesis in petunia flowers.

Elucidating the interaction of carbon, nitrogen, and temperature on the biosynthesis of Aureobasidium pullulans antifungal volatiles.

The combined biochemical impact of carbon, nitrogen and temperature on the biosynthesis of the antifungal volatile organic compounds (VOCs): ethanol, 2-methyl-1-propanol, 3-methyl-1-butanol and 2-phenylethanol produced by Aureobasidium pullulans A1 and A3 was investigated using a Box-Behnken experimental design and response surface methodology (RSM). Normalized peak areas derived from solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis, indicated that initial carbon content had a significant influence on the biosynthesis of ethanol and alcohols with greater than three carbon atoms. This result suggests a dominant activity of the A.pullulans anabolic pathway to biosynthesize three higher alcohols via de novo biosynthesis of amino acids from sugar metabolism. Low concentrations of carbon (3-13 g l-1 ) with nitrogen as both ammonium and amino acids in the growth medium resulted in a higher number of significant linear and quadratic relationships. Nitrogen availability and growth temperature had significant negative linear and quadratic correlations with VOCs biosynthesis in most instances. Isolate-dependant metabolic response was evident for all abiotic parameters tested on alcohol production. The findings of this study offer new perspectives to improve the production of key antifungal compounds by antagonists in biological control systems.

BiClusO: A Novel Biclustering Approach and Its Application to Species-VOC Relational Data.

In this paper, we propose a novel biclustering approach called BiClusO. Biclustering can be applied to various types of bipartite data such as gene-condition or gene-disease relations. For example, we applied BiClusO to bipartite relations between species and volatile organic compounds (VOCs). VOCs, which are emitted by different species, have huge environmental and ecological impacts. The biosynthesis of VOCs depends on different metabolic pathways which can be used to categorize the species. A previous study related to the KNApSAcK VOC database classified microorganisms based on their VOC profiles, which confirmed the consistency between VOC-based and pathogenicity-based classifications. However, due to limited data, classification of all species in terms of VOC profiles was not performed. In this study, we enriched our database with additional data collected from different online sources and journals. Then, by applying BiClusO to species-VOC relational data, we determined that VOC-based classification is consistent with taxonomy-based classification of the species. We also assessed the diversity of VOC pathways across different kingdoms of species.

Ethylene functions as a suppressor of volatile production in rice.

We examined the role of ethylene in the production of rice (Oryza sativa) volatile organic compounds (VOCs), which act as indirect defense signals against herbivores in tritrophic interactions. Rice plants were exposed to exogenous ethylene (1 ppm) after simulated herbivory, which consisted of mechanical wounding supplemented with oral secretions (WOS) from the generalist herbivore larva Mythimna loreyi. Ethylene treatment highly suppressed VOCs in WOS-treated rice leaves, which was further corroborated by the reduced transcript levels of major VOC biosynthesis genes in ethylene-treated rice. In contrast, the accumulation of jasmonates (JA), known to control VOCs in higher plants, and transcript levels of primary JA response genes, including OsMYC2, were not largely affected by ethylene application. At the functional level, flooding is known to promote internode elongation in young rice via ethylene signaling. Consistent with the negative role of ethylene on VOC genes, the accumulation of VOCs in water-submerged rice leaves was suppressed. Furthermore, in mature rice plants, which naturally produce less volatiles, VOCs could be rescued by the application of the ethylene perception inhibitor 1-methylcyclopropene. Our data suggest that ethylene acts as an endogenous suppressor of VOCs in rice plants during development and under stress.