Genomes of the Banyan Tree and Pollinator Wasp Provide Insights into Fig-Wasp Coevolution.

Banyan trees are distinguished by their extraordinary aerial roots. The Ficus genus includes species that have evolved a species-specific mutualism system with wasp pollinators. We sequenced genomes of the Chinese banyan tree, F. microcarpa, and a species lacking aerial roots, F. hispida, and one wasp genome coevolving with F. microcarpa, Eupristina verticillata. Comparative analysis of the two Ficus genomes revealed dynamic karyotype variation associated with adaptive evolution. Copy number expansion of auxin-related genes from duplications and elevated auxin production are associated with aerial root development in F. microcarpa. A male-specific AGAMOUS paralog, FhAG2, was identified as a candidate gene for sex determination in F. hispida. Population genomic analyses of Ficus species revealed genomic signatures of morphological and physiological coadaptation with their pollinators involving terpenoid- and benzenoid-derived compounds. These three genomes offer insights into and genomic resources for investigating the geneses of aerial roots, monoecy and dioecy, and codiversification in a symbiotic system.

Strong isoprene emission response to temperature in tundra vegetation.

Emissions of biogenic volatile organic compounds (BVOCs) are a crucial component of biosphere-atmosphere interactions. In northern latitudes, climate change is amplified by feedback processes in which BVOCs have a recognized, yet poorly quantified role, mainly due to a lack of measurements and concomitant modeling gaps. Hence, current Earth system models mostly rely on temperature responses measured on vegetation from lower latitudes, rendering their predictions highly uncertain. Here, we show how tundra isoprene emissions respond vigorously to temperature increases, compared to model results. Our unique dataset of direct eddy covariance ecosystem-level isoprene measurements in two contrasting ecosystems exhibited Q10 (the factor by which the emission rate increases with a 10 °C rise in temperature) temperature coefficients of up to 20.8, that is, 3.5 times the Q10 of 5.9 derived from the equivalent model calculations. Crude estimates using the observed temperature responses indicate that tundra vegetation could enhance their isoprene emissions by up to 41% (87%)-that is, 46% (55%) more than estimated by models-with a 2 °C (4 °C) warming. Our results demonstrate that tundra vegetation possesses the potential to substantially boost its isoprene emissions in response to future rising temperatures, at rates that exceed the current Earth system model predictions.

Distinguish Esophageal Cancer Cells through VOCs Induced by Methionine Regulation.

Detection of exhaled volatile organic compounds (VOCs) is promising for noninvasive screening of esophageal cancer (EC). Cellular VOC analysis can be used to investigate potential biomarkers. Considering the crucial role of methionine (Met) during cancer development, exploring associated abnormal metabolic phenotypes becomes imperative. In this work, we employed headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) to investigate the volatile metabolic profiles of EC cells (KYSE150) and normal esophageal epithelial cells (HEECs) under a Met regulation strategy. Using untargeted approaches, we analyzed the metabolic VOCs of the two cell types and explored the differential VOCs between them. Subsequently, we utilized targeted approaches to analyze the differential VOCs in both cell types under gradient Met culture conditions. The results revealed that there were five/six differential VOCs between cells under Met-containing/Met-free culture conditions. And the difference in levels of two characteristic VOCs (1-butanol and ethyl 2-methylbutyrate) between the two cell types intensified with the increase of the Met concentration. Notably, this is the first report on VOC analysis of EC cells and the first to consider the effect of Met on volatile metabolic profiles. The present work indicates that EC cells can be distinguished through VOCs induced by Met regulation, which holds promise for providing novel insights into diagnostic strategies.

Widely targeted volatilomics and transcriptome analyses reveal the differences in volatile organic components in differently shaped Amomum tsao-ko fruits.

BACKGROUND: Amomum tsao-ko is an important aromatic crop used in medicines and food. It can be categorized into three main types based on the fruit shape: long (L), oval (O), and round (R). However, limited information is available on the volatile substances present in differently shaped A. tsao-ko fruits. This study investigated the characteristics and biosynthesis of volatile organic compounds (VOCs) in fresh and dried A. tsao-ko fruits of different shapes using widely targeted volatilomics and transcriptome analyses. RESULTS: In total, 978 VOCs, primarily terpenoids, esters, and heterocyclic compounds, were detected. The number of differentially accumulated volatile organic compounds (DAVOCs) in dried fruits of various shapes was significantly higher than that in fresh fruits, with terpenoids, esters, and heterocyclic compounds accounting for approximately 50% of the total DAVOCs. Notably, α-phellandrene, identified as a shared differential accumulated terpenoid across various fruit shapes, was detected in both fresh and dried fruits. Through transcriptome analysis, 40 candidate genes implicated in the terpenoid biosynthesis pathway were screened. An integrated analysis of the metabolome and transcriptome revealed that the structural genes HMGR-2, TPS7, TPS5-10, TPS21-3, TPS21-5, TPS21-6, TPS21-7, and TPS21-9, along with 81 transcription factors (including 17 NACs, 16 MYBs, 16 AP2/ERFs, 13 WRKYs, 13 bHLHs, and 6 bZIPs), co-regulate the biosynthesis of volatile terpenoids. CONCLUSIONS: This study expands our understanding of the volatile metabolism profile of A. tsao-ko and provides a solid foundation for future investigations of the mechanisms governing fruit quality.

Floral scent changes in response to pollen removal are rare in buzz-pollinated Solanum.

MAIN CONCLUSION: One of seven Solanum taxa studied displayed associations between pollen presence and floral scent composition and volume, suggesting buzz-pollinated plants rarely use scent as an honest cue for foraging pollinators. Floral scent influences the recruitment, learning, and behaviour of floral visitors. Variation in floral scent can provide information on the amount of reward available or whether a flower has been visited recently and may be particularly important in species with visually concealed rewards. In many buzz-pollinated flowers, tubular anthers opening via small apical pores (poricidal anthers) visually conceal pollen and appear similar regardless of pollen quantity within the anther. We investigated whether pollen removal changes floral scent composition and emission rate in seven taxa of buzz-pollinated Solanum (Solanaceae). We found that pollen removal reduced both the overall emission of floral scent and the emission of specific compounds (linalool and farnesol) in S. lumholtzianum. Our findings suggest that in six out of seven buzz-pollinated taxa studied here, floral scent could not be used as a signal by visitors as it does not contain information on pollen availability.

Rhythmic histone acetylation acts in concert with day-night oscillation of the floral volatile metabolic network.

The biosynthesis of specialized metabolites is strictly regulated by environmental inputs such as the day-night cycle, but the underlying mechanisms remain elusive. In Petunia hybrida cv. Mitchell flowers, the biosynthesis and emission of volatile compounds display a diurnal pattern with a peak in the evening to attract nocturnal pollinators. Using petunia flowers as a model system, we found that chromatin level regulation, especially histone acetylation, plays an essential role in mediating the day-night oscillation of the biosynthetic gene network of specialized metabolites. By performing time-course chromatin immunoprecipitation assays for histone modifications, we uncovered that a specific group of genes involved in the regulation, biosynthesis, and emission of floral volatile compounds, which displays the greatest magnitude in day-night oscillating gene expression, is associated with highly dynamic histone acetylation marks H3K9ac and H3K27ac. Specifically, the strongest oscillating genes featured a drastic removal of histone acetylation marks at night, potentially to shut down the biosynthesis of floral volatile compounds during the morning when they are not needed. Inhibiting daytime histone acetylation led to a compromised evening induction of these genes. Overall, our study suggested an active role of chromatin modification in the diurnal oscillation of specialized metabolic network.

Natural selection on floral volatiles and other traits can change with snowmelt timing and summer precipitation.

Climate change is disrupting floral traits that mediate mutualistic and antagonistic species interactions. Plastic responses of these traits to multiple shifting conditions may be adaptive, depending on natural selection in new environments. We manipulated snowmelt date over three seasons (3-11 d earlier) in factorial combination with growing-season precipitation (normal, halved, or doubled) to measure plastic responses of volatile emissions and other floral traits in Ipomopsis aggregata. We quantified how precipitation and early snowmelt affected selection on traits by seed predators and pollinators. Within years, floral emissions did not respond to precipitation treatments but shifted with snowmelt treatment depending on the year. Across 3 yr, emissions correlated with both precipitation and snowmelt date. These effects were driven by changes in soil moisture. Selection on several traits changed with earlier snowmelt or reduced precipitation, in some cases driven by predispersal seed predation. Floral trait plasticity was not generally adaptive. Floral volatile emissions shifted in the face of two effects of climate change, and the new environments modulated selection imposed by interacting species. The complexity of the responses underscores the need for more studies of how climate change will affect floral volatiles and other floral traits.

Development of the gas chromatography/mass spectrometry-based aroma designer capable of modifying volatile chemical compositions in complex odors.

Many volatile organic compounds (VOCs) are used to produce various commercial products with aromas mimicking natural products. The VOCs responsible for aromas have been identified from many natural products. The current major strategy is to analyze chemical compositions and aroma qualities of individual VOCs using gas chromatography/mass spectrometry (GC/MS) and GC-olfactometry. However, such analyses cannot determine whether candidate VOCs contribute to the characteristic aroma in mixtures of many VOCs. In this study, we developed a GC/MS-based VOC collection/omission system that can modify the VOC compositions of samples easily and rapidly. The system is composed of GC/MS with a switching unit that can change gas flow routes between MS and a VOC collection device. We first applied this system to prepare gas samples for omission tests, and the aroma qualities of VOC mixtures with and without some VOCs were evaluated by panelists. If aroma qualities were different between the 2 samples, the omitted VOCs were likely key odorants. By collecting VOCs in a gas bag attached to the collection device and transferring some VOCs to MS, specific VOCs could be omitted easily from the VOC mixture. The system could prepare omission samples without chemical identification, preparation of each VOC, and laborious techniques for mixing VOCs, thus overcoming the limitations of previous methods of sample preparation. Finally, the system was used to prepare artificial aromas by replacing VOC compositions between different samples for screening of key odorants. In conclusion, the system developed here can improve aroma research by identifying key odorants from natural products.

Diurnal patterns of floral volatile emissions in three species of Narcissus.

PREMISE: Plants generate a wide array of signals such as olfactory cues to attract and manipulate the response of pollinators. The present study addresses the temporal patterns of scent emission as an additional dimension to the scent composition. The expectation is that divergent floral function is reflected in divergent qualitative and temporal emission patterns. METHODS: We used GC-ion mobility spectrometry with an integrated pre-concentration for automated acquisition of the temporal trends in floral volatile emissions for N. viridiflorus, N. papyraceus, and N. cantabricus subsp. foliosus. RESULTS: We found a considerable increase in scent emissions and changes in scent composition for N. viridiflorus at night. This increase was particularly pronounced for aromatic substances such as benzyl acetate and p-cresol. We found no diurnal patterns in N. papyraceus, despite a similar qualitative composition of floral volatiles. Narcissus cantabricus subsp. foliosus showed no diurnal patterns either and differed considerably in floral scent composition. CONCLUSIONS: Scent composition, circadian emission patterns, and floral morphology indicate divergent, but partially overlapping pollinator communities. However, the limited pollinator data from the field only permits a tentative correlation between emission patterns and flower visitors. Narcissus papyraceus and N. cantabricus show no clear diurnal patterns and thus no adjustment to the activity patterns of their diurnal pollinators. In N. viridiflorus, timing of scent emission indicates an adaptation to nocturnal flower visitors, contradicting Macroglossum as the only reported pollinator. We propose that the legitimate pollinators of N. viridiflorus are nocturnal and are still unidentified.

Advancing Breathomics through Accurate Discrimination of Endogenous from Exogenous Volatiles in Breath.

Breathomics, a growing field in exposure monitoring and clinical diagnostics, has faced accuracy challenges due to unclear contributing factors. This study aims to enhance the potential of breathomics in various frontiers by categorizing exhaled volatile organic compounds (VOCs) as endogenous or exogenous. Analyzing ambient air and breath samples from 271 volunteers via TD-GC × GC-TOF MS/FID, we identify and quantify 50 common VOCs in exhaled breath. Advanced quantitative structure-property relationships and compartment models are employed to obtain VOCs kinetic parameters. This in-depth approach allows us to accurately determine the alveolar concentration of VOCs and further discern their origins, facilitating personalized application of breathomics in exposure assessment and disease diagnosis. Our findings demonstrate that prolonged external exposure turns humans into secondary pollutant sources. Analysis of endogenous VOCs reveals that internal exposure poses more significant health risks than external. Moreover, by correcting environmental backgrounds, we improve the accuracy of gastrointestinal disease diagnostic models by 15-25%. This advancement in identifying VOC origins via compartmental models promises to elevate the clinical relevance of breathomics, marking a leap forward in exposure assessment and precision medicine.

Boosting Catalytic and Anti-fluorination Performance of the Ru/Vanadia-Titania Catalyst for the Oxidative Destruction of Freon by Sulfuric Acid Modification.

Chlorofluorocarbons (CFCs) exert a strong greenhouse effect and constitute the largest contributor to ozone depletion. Catalytic removal is considered an effective pathway for eliminating low-concentration CFCs under mild conditions. The key issue is the easy deactivation of the catalysts due to their surface fluorination. We herein report a comparative investigation on catalytic dichlorodifluoromethane (CFC-12) removal in the absence or presence of water over the sulfuric-acid-modified three-dimensionally ordered macroporous vanadia-titania-supported Ru (S-Ru/3DOM VTO) catalysts. The S-Ru/3DOM VTO catalyst exhibited high activity (T90% = 278 °C at space velocity = 40 000 mL g-1 h-1) and good stability within 60 h of on-stream reaction in the presence of 1800 ppm of water due to the improvements in acid site amount and redox ability that promoted the adsorption of CFC-12 and the activation of C-F bonds. Compared with the case under dry conditions, catalytic performance for CFC-12 removal was better over the S-Ru/3DOM VTO catalyst in the presence of water. Water introduction mitigated surface fluorination by the replenishment of hydroxyl groups, inhibited the formation of halogenated byproducts via the surface fluorine species cleaning effect, and promoted the reaction pathway of COX2 (X = Cl/F) → carboxylic acid → CO2.

Identification of Stutzerimonas stutzeri volatile organic compounds that enhance the colonization and promote tomato seedling growth.

AIMS: Volatile organic compounds (VOCs) have an important function in plant growth-promoting rhizobacteria (PGPR) development and plant growth. This study aimed to identify VOCs of the PGPR strain, Stutzerimonas stutzeri NRCB010, and investigate their effects on NRCB010 biofilm formation, swarming motility, colonization, and tomato seedling growth. METHODS AND RESULTS: Solid-phase microextraction and gas chromatography-mass spectrometry were performed to identify the VOCs produced during NRCB010 fermentation. A total of 28 VOCs were identified. Among them, seven (e.g. γ-valerolactone, 3-octanone, mandelic acid, 2-heptanone, methyl palmitate, S-methyl thioacetate, and 2,3-heptanedione), which smell well, are beneficial for plant, or as food additives, and without serious toxicities were selected to evaluate their effects on NRCB010 and tomato seedling growth. It was found that most of these VOCs positively influenced NRCB010 swarming motility, biofilm formation, and colonization, and the tomato seedling growth. Notably, γ-valerolactone and S-methyl thioacetate exhibited the most positive performances. CONCLUSION: The seven NRCB010 VOCs, essential for PGPR and crop growth, are potential bioactive ingredients within microbial fertilizer formulations. Nevertheless, the long-term sustainability and replicability of the positive effects of these compounds across different soil and crop types, particularly under field conditions, require further investigation.

Wearing face masks as a potential source for inhalation and oral uptake of inanimate toxins - A scoping review.

BACKGROUND: From 2020 to 2023 many people around the world were forced to wear masks for large proportions of the day based on mandates and laws. We aimed to study the potential of face masks for the content and release of inanimate toxins. METHODS: A scoping review of 1003 studies was performed (database search in PubMed/MEDLINE, qualitative and quantitative evaluation). RESULTS: 24 studies were included (experimental time 17 min to 15 days) evaluating content and/or release in 631 masks (273 surgical, 228 textile and 130 N95 masks). Most studies (63%) showed alarming results with high micro- and nanoplastics (MPs and NPs) release and exceedances could also be evidenced for volatile organic compounds (VOCs), xylene, acrolein, per-/polyfluoroalkyl substances (PFAS), phthalates (including di(2-ethylhexyl)-phthalate, DEHP) and for Pb, Cd, Co, Cu, Sb and TiO2. DISCUSSION: Of course, masks filter larger dirt and plastic particles and fibers from the air we breathe and have specific indications, but according to our data they also carry risks. Depending on the application, a risk-benefit analysis is necessary. CONCLUSION: Undoubtedly, mask mandates during the SARS-CoV-2 pandemic have been generating an additional source of potentially harmful exposition to toxins with health threatening and carcinogenic properties at population level with almost zero distance to the airways.

Non-Invasive Multi-Gas Detection Enabled by Cu-CuO/PEDOT Microneedle Sensor.

Metal-oxide-based gas sensors are extensively utilized across various domains due to their cost-effectiveness, facile fabrication, and compatibility with microelectronic technologies. The copper (Cu)-based multifunctional polymer-enhanced sensor (CuMPES) represents a notably tailored design for non-invasive environmental monitoring, particularly for detecting diverse gases with a low concentration. In this investigation, the Cu-CuO/PEDOT nanocomposite was synthesized via a straightforward chemical oxidation and vapor-phase polymerization. Comprehensive characterizations employing X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and micro Raman elucidated the composition, morphology, and crystal structure of this nanocomposite. Gas-sensing assessments of this CuMPES based on Cu-CuO/PEDOT revealed that the response current of the microneedle-type CuMPES surpassed that of the pure Cu microsensor by nearly threefold. The electrical conductivity and surface reactivity are enhanced by poly (3,4-ethylenedioxythiophene) (PEDOT) polymerized on the CuO-coated surface, resulting in an enhanced sensor performance with an ultra-fast response/recovery of 0.3/0.5 s.

Low-Cost Sensor System for Air Purification Process Evaluation.

With the development of civilisation, the awareness of the impact of versatile aerosol particles on human health and the environment is growing. New advanced materials and techniques are needed to purify the air to reduce this impact. This brings the necessity of fast and low-cost devices to evaluate the air quality from particulate and gaseous impurities, especially in a place where gas chromatography (GC) techniques are unavailable. Small portable and low-cost systems may work separately or be incorporated into devices responsible for air-cleaning processes, such as filters, smoke adsorbers, or plasma air cleaners. Given the above, this study proposes utilising a self-assembled low-cost system to evaluate air quality, which can be used in many outdoor and indoor applications. ESP32 boards with the wireless communication protocol ESP-NOW were used as the framework of the system. The concentration of aerosol particles was measured using Alphasense sensors. The concentrations of the following gases were measured: NO2, SO2, O3, CO, CO2, and H2S. The system was used to evaluate the quality of air containing tobacco smoke after passing through an actual DBD plasma reactor where the purification occurred. A high amount of reduction in aerosol particles and a reduction in the SO2 concentration were detected. An increase in the NO2 concentration was seen as an undesirable effect. The aerosol particle measurements were compared with those using a professional device (GRIMM, Hamburg, Germany), which showed the same trends in aerosol particle behaviour. The obtained results are auspicious and are a step towards producing a low-cost, efficient system for evaluating air quality as well as indoor and outdoor conditions.

Enhanced TiO2-Based Photocatalytic Volatile Organic Compound Decomposition Combined with Ultrasonic Atomization in the Co-Presence of Carbon Black and Heavy Metal Nanoparticles.

Volatile organic compounds (VOCs) are representative indoor air pollutants that negatively affect the human body owing to their toxicity. One of the most promising methods for VOC removal is photocatalytic degradation using TiO2. In this study, the addition of carbon black (CB) and heavy metal nanoparticles (NPs) was investigated to improve the efficiency of a TiO2-based photocatalytic VOC decomposition system combined with ultrasonic atomization and ultraviolet irradiation, as described previously. The addition of CB and Ag NPs significantly improved the degradation efficiency. A comparison with other heavy metal nanoparticles and their respective roles are discussed.

PdPtVOx/CeO2-ZrO2: Highly efficient catalysts with good sulfur dioxide-poisoning reversibility for the oxidative removal of ethylbenzene.

The PdPtVOx/CeO2-ZrO2 (PdPtVOx/CZO) catalysts were obtained by using different approaches, and their physical and chemical properties were determined by various techniques. Catalytic activities of these materials in the presence of H2O or SO2 were evaluated for the oxidation of ethylbenzene (EB). The PdPtVOx/CZO sample exhibited high catalytic activity, good hydrothermal stability, and reversible sulfur dioxide-poisoning performance, over which the specific reaction rate at 160°C, turnover frequency at 160°C (TOFPd or Pt), and apparent activation energy were 72.6 mmol/(gPt⋅sec) or 124.2 mmol/(gPd⋅sec), 14.2 sec-1 (TOFPt) or 13.1 sec-1 (TOFPd), and 58 kJ/mol, respectively. The large EB adsorption capacity, good reducibility, and strong acidity contributed to the good catalytic performance of PdPtVOx/CZO. Catalytic activity of PdPtVOx/CZO decreased when 50 ppm SO2 or (1.0 vol.% H2O + 50 ppm SO2) was added to the feedstock, but was gradually restored to its initial level after the SO2 was cut off. The good reversible sulfur dioxide-resistant performance of PdPtVOx/CZO was associated with the facts: (i) the introduction of SO2 leads to an increase in surface acidity; (ii) V can adsorb and activate SO2, thus accelerating formation of the SOx2- (x = 3 or 4) species at the V and CZO sites, weakening the adsorption of sulfur species at the PdPt active sites, and hence protecting the PdPt active sites to be not poisoned by SO2. EB oxidation over PdPtVOx/CZO might take place via the route of EB â†’ styrene â†’ phenyl methyl ketone â†’ benzaldehyde â†’ benzoic acid â†’ maleic anhydride â†’ CO2 and H2O.

Research Progress of Using Canine Olfactory Search for Human Remains.

In the process of murder investigation, it is of great significance to find the discarded and buried human remains accurately. The main methods of searching for human remains include human visual search, aerial detection, geophysical technology, remote imaging technology and canine olfactory search technique. Canine olfactory search for human remains is a recognized time-effective and non-invasive search method, making dogs the most valuable search tool in forensic investigation. By systematically reviewing and summarizing relevant literature, and based on the theory of volatile organic compound produced by the decomposition of human remains, this paper explores the basic principle of the canine olfactory search technique for human remains. This paper also reviews the application of training canine search technique for human remains in forensic investigation by using human blood, tissue, cadaver putrefying fluid and odor substitutes as sniffing sources. The application prospect of canine olfactory search for human remains was prospected from the perspectives of detection of volatile organic compound during cadaver decay, development of odor substitutes and adsorption devices, and technology tactics used in canine training and use, to provide references for the relevant research of canine olfactory search for human remains in China.

Characterization of a Bacillus subtilis S-16 Thiazole-Synthesis-Related Gene thiS Knockout and Antimicrobial Activity Analysis.

Bacillus subtilis S-16 isolated from sunflower-rhizosphere soil is an effective biocontrol agent for preventing soilborne diseases in plants. Previous research revealed that the volatile organic compounds (VOCs) produced by the S-16 strain have strong inhibitory effects on Sclerotinia sclerotiorum. The identification of the VOCs of S-16 using gas chromatography-tandem mass spectrometry (GC-MS/MS) revealed 35 compounds. Technical-grade formulations of four of these compounds were chosen for further study: 2-pentadecanone, 6,10,14-trimethyl-2-octanone, 2-methyl benzothiazole (2-MBTH), and heptadecane. The major constituent, 2-MBTH, plays an important role in the antifungal activity of the VOCs of S-16 against the growth of Sclerotinia sclerotiorum. The purpose of this study was to determine the impact of the thiS gene's deletion on the 2-MBTH production and to conduct an antimicrobial activity analysis of the Bacillus subtilis S-16. The thiazole-biosynthesis gene was deleted via homologous recombination, after which the contents of 2-MBTH in the wild-type and mutant S-16 strains were analyzed using GC-MS. The antifungal effects of the VOCs were determined using a dual-culture technique. The morphological characteristics of the Sclerotinia sclerotiorum mycelia were examined via scanning-electron microscopy (SEM). Additionally, the lesion areas on the sunflower leaves with and without treatment with the VOCs from the wild-type and mutant strains were measured to explore the effects of the VOCs on the virulence of the Sclerotinia sclerotiorum. Moreover, the effects of the VOCs on the sclerotial production were assessed. We showed that the mutant strain produced less 2-MBTH. The ability of the VOCs produced by the mutant strain to inhibit the growth of the mycelia was also reduced. The SEM observation showed that the VOCs released by the mutant strain also caused more flaccid and gapped hyphae in the Sclerotinia sclerotiorum. The Sclerotinia sclerotiorum treated by the VOCs produced by the mutant strains caused more damage to the leaves than that treated by the VOCs produced by the wild type and the mutant-strain-produced VOCs inhibited sclerotia formation less. The production of 2-MBTH and its antimicrobial activities were adversely affected to varying degrees by the deletion of thiS.

Pipecolic acid synthesis is required for systemic acquired resistance and plant-to-plant-induced immunity in barley.

Defense responses in plants are based on complex biochemical processes. Systemic acquired resistance (SAR) helps to fight infections by (hemi-)biotrophic pathogens. One important signaling molecule in SAR is pipecolic acid (Pip), accumulation of which is dependent on the aminotransferase ALD1 in Arabidopsis. While exogenous Pip primes defense responses in the monocotyledonous cereal crop barley (Hordeum vulgare), it is currently unclear if endogenous Pip plays a role in disease resistance in monocots. Here, we generated barley ald1 mutants using CRISPR/Cas9, and assessed their capacity to mount SAR. Endogenous Pip levels were reduced after infection of the ald1 mutant, and this altered systemic defense against the fungus Blumeria graminis f. sp. hordei. Furthermore, Hvald1 plants did not emit nonanal, one of the key volatile compounds that are normally emitted by barley plants after the activation of SAR. This resulted in the inability of neighboring plants to perceive and/or respond to airborne cues and prepare for an upcoming infection, although HvALD1 was not required in the receiver plants to mediate the response. Our results highlight the crucial role of endogenous HvALD1 and Pip for SAR, and associate Pip, in particular together with nonanal, with plant-to-plant defense propagation in the monocot crop barley.