Biosynthesis, function and metabolic engineering of plant volatile organic compounds

Impact of microplastics on plant biogenic volatile organic compounds emission: A preliminary study

Plants produce biogenic volatile organic compounds (BVOCs) that are essential for interacting with the environment. As emerging pollutants, microplastics (MPs) may influence BVOCs emissions, yet their effects remain poorly underexplored. This study employed headspace solid phase microextraction coupled with gas chromatography - mass spectrum to investigate the impact of MPs on the BVOC emission profiles of lettuce (Lactuca sativa). Our results demonstrated that polystyrene (PS) MPs exposure, even at environmental concentrations (0.5-2 mg/L), significantly altered BVOC profiles, with a marked increase in aldehydes and ketones. A 7-fold increase in phenylacetaldehyde and benzaldehyde at 50 mg/L indicated stress-related metabolic changes, which also evidenced by reduced superoxide dismutase (SOD) activity and shifts in root microbial communities. The key discriminating BVOCs identified suggest that the presence of MPs impact plant survival and adaptability, with emissions originating from various metabolic pathways, including phenylpropanoid, lipoxygenase, and terpenoid synthesis pathways. Furthermore, variations in type, size, and aging treatment of MPs influenced BVOCs emission patterns. Our findings underscore the significance of BVOCs as indicators of exposure risks associated with MPs and highlight the ecological threats posed by these pollutants.

BVOC emissions from Posidonia oceanica, the most abundant Mediterranean seagrass species

Biogenic Volatile Organic Compounds (BVOCs) are important precursors of tropospheric atmospheric pollutants such as ozone and secondary organic aerosols. Thus, it is crucial to characterize BVOCs sources at regional and global scales. Marine environments, especially benthic ecosystems, are still overlooked although they can produce a wide range of BVOCs. In this study, BVOCs emissions from Posidonia oceanica, the main seagrass species in the Mediterranean Sea, were characterised over several days using dynamic enclosure systems. A total of 105 different compounds were detected through PTR-ToF-MS and GC-MS analyses (after checking compounds correspondence between both analyses) and included terpenoids (isoprene), sulfur- (dimethyl sulfide (DMS)), halogenenated- (chloromethane), and oxygenated compounds (methanol, acetone). High BVOCs emissions were measured (up to 10 and 4 μg.gDW-1.h-1 for DMS and acetone, respectively), in the same ranges reported for terrestrial plant species. Most BVOCs followed diurnal cycles with higher emissions during the day compared to night, although nocturnal emissions were also detected. Surprisingly, DMS emissions showed an opposite pattern with higher emissions at night. Uptakes were recorded for formic acid all through the day, at night for acetonitrile and only punctually for most other BVOCs. Our results strongly suggest that P. oceanica meadows are important contributors to the regional BVOCs budget in the Mediterranean basin.

Integrative omics reveals mechanisms of biosynthesis and regulation of floral scent in Cymbidium tracyanum

Flower scent is a crucial determiner in pollinator attraction and a significant horticultural trait in ornamental plants. Orchids, which have long been of interest in evolutionary biology and horticulture, exhibit remarkable diversity in floral scent type and intensity. However, the mechanisms underlying floral scent biosynthesis and regulation in orchids remain largely unexplored. In this study, we focus on floral scent in Cymbidium tracyanum, a wild species known for its strong floral fragrance and as a primary breeding parent of commercial Cymbidium hybrids. We present a chromosome-level genome assembly of C. tracyanum, totaling 3.79 Gb in size. Comparative genomic analyses reveal significant expansion of gene families associated with terpenoid biosynthesis and related metabolic pathways in C. tracyanum. Integrative analysis of genomic, volatolomic and transcriptomic data identified terpenoids as the predominant volatile components in the flowers of C. tracyanum. We characterized the spatiotemporal patterns of these volatiles and identified CtTPS genes responsible for volatile terpenoid biosynthesis, validating their catalytic functions in vitro. Dual-luciferase reporter assays, yeast one-hybrid assays and EMSA experiments confirmed that CtTPS2, CtTPS3, and CtTPS8 could be activated by various transcription factors (i.e., CtAP2/ERF1, CtbZIP1, CtMYB2, CtMYB3 and CtAP2/ERF4), thereby regulating the production of corresponding monoterpenes and sesquiterpenes. Our study elucidates the biosynthetic and regulatory mechanisms of floral scent in C. tracyanum, which is of great significance for the breeding of fragrant Cymbidium varieties and understanding the ecological adaptability of orchids. This study also highlights the importance of integrating multi-omics data in deciphering key horticultural traits in orchids.

Comparison of key floral components between two Tilia species and among different processing technologies as revealed by widely targeted metabolomic profiling

BACKGROUND

Tilia has a long history of cultivation and holds high ornamental and economic value. The volatile aroma compounds of Tilia flowers have significant characteristics that contribute to their ornamental appeal, and affect the flavor of floral tea. Here, widely targeted metabolomic analyses were conducted to investigate the aroma active compounds in the fresh inflorescences of Tilia cordata Mill. (Tc) and Tilia miqueliana Maxim. (Tm), and in samples prepared by freeze drying, air drying, and oven drying.

RESULTS

We identified 442 volatile organic compounds by headspace solid-phase microextraction gas chromatography-mass spectrometry. Terpenoids were the most abundant and diverse group, while heterocyclic compounds were the main contributors to the aroma profile. Notably, 46 aroma compounds were identified as primary contributors to the characteristic aroma of Tilia, including abhexon, 2-isobutyl-3-methoxypyrazine, (Z)-6-nonenal, methyl benzoate, (E)-2-hexenal, 1-hexanol, 2-thiophenemethanethiol, p-cymene, furaneol, and (Z)-4-heptenal. The concentration of volatile organic compounds was higher in Tc than in Tm, indicating a more pronounced aroma character of Tc. For both Tc and Tm, the aroma compounds were better preserved and present at higher concentrations in freeze-dried samples than in air-dried and oven-dried samples.

CONCLUSION

These results provide a foundation for further research on the molecular mechanisms of aroma formation in Tilia flowers and on aroma as a cue for insect pollination. Furthermore, the results provide a basis for the development and commercialization of Tilia floral teas and other related products. © 2025 Society of Chemical Industry.

Air pollution and its role in the rising burden of type 2 diabetes in India: urgent call for action

India is rapidly becoming the global epicenter of type 2 diabetes (T2D), a complex disease influenced by multiple factors including diet, lifestyle, urbanization, genetics, and environmental exposures such as air pollution. The rapid pace of urbanization, coupled with growing population density, exacerbates air pollution levels in major Indian cities, with pollutants such as particulate matter (PM2.5), (PM10), nitrogen dioxide (NO2), nitrogen oxides (NOX), and carbon monoxide (CO) being significantly elevated in comparison with the rural areas. These pollutants have been implicated in the pathogenesis of T2D, by inducing insulin resistance, oxidative stress, and endothelial dysfunction leading to vascular complications of T2D. International studies also highlight a similar association between air pollution and the incidence of T2D. The multifactorial nature of the disease, combined with the myriad of contributing environmental and lifestyle factors, makes it challenging to pinpoint specific risk elements. To mitigate the impact of these combined factors, continuous monitoring of air quality is imperative. Monitoring of traffic emissions, promotion of electric vehicles (EVs), and enhancement of mass transit options can each mitigate the impact of air pollution on type 2 diabetes. Furthermore, the integration of artificial intelligence (AI) and machine learning (ML) can optimize these interventions, making them even more effective. Urban planning strategies focused on increasing green spaces, afforestation, and sustainable construction practices are essential for long term health benefits. Collectively, these solutions present a holistic approach to combating T2D and improving public health amidst the challenges posed by urbanization and environmental pollution in India.

Field Asymmetric Ion Mobility Spectrometry for Early Detection of Aphanomyces Root Rot in Peas Using Volatile Biomarkers

Volatile organic compounds (VOCs) produced by plants during plant-pathogen interactions can be highly informative for early disease detection. The real-time capability of field asymmetric ion mobility spectrometry (FAIMS) offers a valuable opportunity to monitor plant VOCs nondestructively and dynamically. This study evaluated the FAIMS system reliability in measuring VOC profiles for an early diagnosis of Aphanomyces root rot (ARR) in pea (Pisum sativum L.). This evaluation utilized pea lines with a major quantitative trait locus (QTL Ae-Ps7.6) and lines without QTL, identified to provide partial resistance against ARR. For the first time, a VOC biomarker associated with ARR was detected as early as 2 days after inoculation (DAI). Furthermore, at 7 DAI, one of the biomarkers showed significant differences between lines with and without QTL Ae-Ps7.6 in the noninoculated samples. These findings demonstrate the potential applicability of the FAIMS system as a valuable tool for detecting volatile biomarkers for early plant disease detection.

The plant-beneficial fungus Trichoderma harzianum T22 modulates plant metabolism and negatively affects Nezara viridula

BACKGROUND

Plant-beneficial fungi play an important role in enhancing plant health and resistance against biotic and abiotic stresses. Although extensive research has focused on their role in eliciting plant defences against pathogens, their contribution to induced resistance against herbivorous insects and the underlying mechanisms remain poorly understood. In this study, we used insect bioassays and untargeted metabolomics to investigate the impact of root inoculation of sweet pepper with the plant-beneficial fungus Trichoderma harzianum T22 on direct defence responses against the insect herbivore Nezara viridula.

RESULTS

We observed reduced relative growth rate of N. viridula on leaves of fungus-inoculated plants, with no change in mortality. Untargeted metabolomic analyses revealed that inoculation with T. harzianum did not affect the leaf metabolome in the absence of herbivory five weeks after inoculation. However, compared to non-inoculated plants, inoculated plants exhibited significant metabolic alterations in herbivore-damaged leaves following N. viridula feeding, while changes in the metabolic profile of distant leaves were less pronounced. Notably, metabolites involved in the shikimate-phenylpropanoid pathway, known to be involved in plant defence responses, displayed higher accumulation in damaged leaves of inoculated plants compared to non-inoculated plants.

CONCLUSION

Our results indicate that root inoculation with T. harzianum T22 affects plant defences against N. viridula, leading to reduced insect performance. Metabolite-level effects were primarily observed in damaged leaves, suggesting that the priming effect mainly results in localized metabolite accumulation at the site of attack. Future research should focus on identifying the detected compounds and determining their role in impairing N. viridula performance.

Comparative transcriptomic analysis of loquat floral fragrance and hormone synthesis regulation across developmental stages in petals and stamens

Introduction

Loquat Eriobotrya japonica is a native plant in China that blooms at low temperatures in early winter, and the floral fragrance volatiles from the petals and stamens of loquats' flowers are attractive to wild pollinators like Chinese honeybees. Thus, it was necessary to reveal the biosynthesis of floral fragrance and hormone regulation involved in the insect pollination of loquats' flowers.

Methods

Here, the volatile contents of petals and stamens were significantly higher than those of other parts of the loquat flower through the analysis of GC, and a key loquat flowers' compound 4-methoxybenzaldehyde has the highest content among all volatile components. The transcriptomics of six samples of loquat flowers' petals and stamens at different developmental stages of bud (Bu), exposed (Ex), and bloom (Bl) were obtained.

Results

PCA analysis indicates that petals developed earlier than stamens due to the number of up-regulated petal genes being much higher than that of stamens in the bud stage, and the number of up-regulated stamen genes increasing rapidly at the stages of exposed and bloom. KEGG analysis revealed that petals and stamens DEGs were enriched in two pathways of plant hormone signal transduction and phenylpropanoid biosynthesis. Among them, some key genes related to the synthesis of the fragrance components were screened, and showing a strong positive correlation with phenethyl alcohol and 4-methoxybenzaldehyde. The synthesis of hormones such as gibberellin and growth hormone were also screened. Finally, real-time PCR was used to validate the screening of 12 genes related to floral fragrance and hormone synthesis. Except for ACO (1-Aminocyclopropane-1-carboxylate oxidase), most other genes located in the petals were expressed in significantly higher abundance than in the stamens. Among these, the expression of PAAS (Phenylacetaldehyde synthetase), OMT (O-methyltransferase), GA2OX (Gibberellin 2-β-dioxygenase) were consistent with the development of loquat flower.

Discussion

Their high expression promoted the synthesis and release of floral fragrance and then may effectively attract pollinators. This study enriches the molecular mechanism of the release, synthesis and regulation of loquat floral fragrances and provides a theoretical basis for the co-evolutionary pollination between Chinese honey bees and loquat flowers in early winter.

Deciphering the flavor profile and seasonal variation of black tea processed from cultivar 'Baiye 1'

Black tea flavor is predominantly shaped by the internal composition of the materials utilized, and black teas produced from high-polyphenol varieties is typically characterized by a stronger, bitter, astringent taste with a low aroma intensity. Therefore, understanding the flavor profile and material basis of black tea produced from high-amino acids tea plants may be helpful to enhance flavor and innovate black tea products. Here, by sensory evaluation and metabolomics analysis, it was found that the typical flavor of 'Baiye 1' black tea (BYBT) was orange-red solution color, a sweet potato-like or sweet honey-like aroma, and a sweet, umami, and light taste. A total of 110 characteristic volatiles of BYBT were identified, among which 29 metabolites, including β-ionone with a sweet aroma, may be considered the key compounds responsible for the sweet aroma. The geraniol, cis-3-hexenyl isovalerate, and n-valeric acid cis-3-hexenyl were key volatiles that distinguish different seasons. Additionally, 7 volatiles, including β-ocimene, geraniol, citral, were the crucial metabolites responsible for the stronger sweet or honey aroma of BYBT in spring. The lower tea polyphenols and the higher amino acids and sugars shaped the BYBT profile with distinct umami and sweetness, as well as a light taste. Amino acids, catechins and their derivatives were the most significantly affected by seasonal variations in BYBT, and were also responsible for the differences in taste and color quality observed between samples with different seasons. The findings of this study provided a scientific foundation for the development of novel black tea products or derivatives thereof.

Comprehensive review of sweetpotato flavor compounds: Opportunities for developing consumer-preferred varieties

Flavor contributes significantly to consumer preferences of cooked sweetpotato. Sugars largely drive the sweet taste, while the volatile organic compounds (VOCs), mainly classified as alcohols, aldehydes, ketones, and terpenes, provide characteristic aromas and influence the overall perception of flavor. In this paper, we review sweetpotato VOCs identified in the literature from 1980 to 2024 and discuss the efforts to understand how these compounds influence sensory perception and consumer preferences. Over 400 VOCs have been identified in cooked sweetpotato with 76 known to be aroma-active. Most of these aroma-active compounds are generated from Maillard reactions, Strecker, lipid and carotenoid degradation, or thermal release of terpenes from glycosidic bonds during cooking. Suggested mechanisms of formation of these aroma-active compounds are described. However, specific VOCs that are responsible for different aromas and flavors in cooked sweetpotatoes are yet to be fully characterized. There are significant opportunities to further identify the key predictors of aroma and flavor attributes in sweetpotato, which can be used to enhance the quality of existing varieties and develop new ones using a wide range of genetic tools. This review summarizes 44 years of research aimed at identifying key aroma compounds in cooked sweetpotato and provides a roadmap for future studies to guide breeders in developing high-quality, consumer-preferred varieties.

Floral scent emission of Epiphyllum oxypetalum: discovery of its cytosol-localized geraniol biosynthesis

Epiphyllum oxypetalum, a renowned ornamental species in Cactaceae, releases attractive fragrance during its infrequent, transient, and nocturnal blooms. However, the floral fragrance composition and biosynthesis remain largely unexplored. Employing volatilomics, transcriptomics, and biochemistry, we systematically characterized the composition, emission dynamics, and biosynthesis of the floral scent of E. oxypetalum. The floral scent composition of E. oxypetalum was highly dynamic. Starting after 8 p.m. local time, volatile emission increased 200-fold within 6 h. At full bloom, geraniol accounted for 72.54% of the total emission, followed by benzyl alcohol (12.96%) and methyl salicylate (3.75%). These scents predominantly originated from petals and sepals. Transcriptomic analysis and inhibition assays using pathway-specific inhibitors revealed that the mevalonate pathway was the precursor source for geraniol biosynthesis. Functionally characterized cytosol-localized geraniol synthase EoTPSa1 was the key enzyme responsible for geraniol biosynthesis. Together, these findings pinpoint a cytosolic biosynthetic route for the major scent volatile geraniol in E. oxypetalum. Our study provides new insights into the emission dynamics and biosynthesis of E. oxypetalum floral scents. In particular, we demonstrate a distinctive mevalonate pathway-based geraniol biosynthetic pathway, which may hold potential for the development of novel perfume products.

A Review of Biogenic Volatile Organic Compounds from Plants: Research Progress and Future Prospects

Biogenic volatile organic compounds (BVOCs) emitted by plants contribute to secondary air pollution through photochemical reactions in sunlight. Due to the influence of multiple factors, accurately characterizing and quantifying the emission of BVOCs from plant sources is challenging, which poses significant obstacles to the effective management and control of BVOCs. Therefore, this paper summarizes the emission mechanisms of BVOCs from plants, explores the primary factors influencing variations in the emission rates of these compounds, and evaluates the advantages and limitations of contemporary "measurement-modeling" methods for characterizing BVOC emissions. It is concluded that current measurement techniques still need to be further developed to meet the criteria of simplicity, affordability, and high precision simultaneously, and in terms of modeling and prediction studies, there is a lack of in-depth research on the atmospheric chemistry of BVOCs and the synergistic effects of multiple factors. Finally, it is suggested to leverage interdisciplinary strengths to develop advanced measurement technologies and high-resolution models for monitoring volatile compounds. Additionally, strategically selecting low-BVOC tree species in pollution-vulnerable urban areas-contingent on rigorous ecological assessments-combined with stringent controls on anthropogenic precursors (e.g., anthropogenic volatile organic compounds (AVOCs)) could serve as a complementary measure to mitigate secondary pollution.

Application and Progress of Genomics in Deciphering the Genetic Regulation Mechanisms of Plant Secondary Metabolites

This review aims to systematically dissect the genetic regulatory mechanisms of plant secondary metabolites in the era of genomics, while comprehensively summarizing the progress and potential impact of genomics in plant secondary metabolism research. By integrating methodologies such as high-throughput sequencing, structural genomics, comparative genomics, and functional genomics, we elucidate the principles underlying plant secondary metabolism and identify functional genes. The application of these technologies has deepened our understanding of secondary metabolic pathways and driven advancements in plant molecular genetics and genomics. The development of genomics has enabled scientists to gain profound insights into the biosynthetic pathways of secondary metabolites in plants such as ginseng (Panax ginseng) and grapevine (Vitis vinifera), while offering novel possibilities for precise regulation of these pathways. Despite remarkable progress in studying the genetic regulation of plant secondary metabolites, significant challenges persist. Future research must focus on integrating multi-omics data, developing advanced bioinformatics tools, and exploring effective genetic improvement strategies to fully harness the medicinal potential of plants and enhance their capacity to synthesize secondary metabolites.

A Comprehensive Review of Plant Volatile Terpenoids, Elucidating Interactions with Surroundings, Systematic Synthesis, Regulation, and Targeted Engineering Production

Plants require a flexible avoidance mechanism as they need to cope with external stimuli and challenges through complex specialized metabolites, among which volatile terpenoids make outstanding contributions, acting as key media signal substances in the cooperation between plants and surrounding organisms. In recent decades, the research on the identification and functional characterization of terpenoid synthase and factors regulating metabolic shunts has gained significant attention, leading to substantial progress and notable achievements. However, with the popularization of terpenoids in insect and disease prevention, medical care, cosmetics, and other fields, coupled with increasing resistance to artificially produced chemical products, the demand for natural terpenoids has outpaced supply, prompting the emergence and popularity of targeted engineering for the mass production of terpenoids using microorganisms and plants as platforms. In this paper, we provide a detailed overview of the key knowledge and research progress of volatile terpenoids with regard to multiple functions, complex synthetic pathways, key terpenoid synthase genes, related regulatory factors, and target engineering.

Biogenic volatile organic compounds from marine benthic organisms: a review

Biogenic Volatile Organic Compounds (BVOCs) play crucial roles in terrestrial environments, acting as defense compounds against environmental stresses and as chemical cues in species interactions. These roles were mainly highlighted on terrestrial plants whereas marine BVOCs are still understudied except dimethyl sufide (DMS) or isoprene. However, recent research highlights that marine organisms, particularly phytoplankton, and to a lesser extent benthic organisms such as macroalgae, seagrasses, and corals, also produce and emit a larger panel of BVOCs. In this review, we compiled and analyzed articles focusing on BVOCs production and emission by benthic photosynthetic organisms. Our review synthesizes current knowledge on the BVOCs produced or emitted by these species, categorized by compounds classes, geographic location and sampling methods. This synthesis provides a preliminary overview of the chemical diversity among benthic organisms, indicating rich and varied BVOCs profiles that warrants further investigation. Furthermore, we explore the potential physiological and ecological roles of BVOCs in benthic ecosystems, discussing their implications for environmental stress responses and interspecies communication. This review underscores the need for more comprehensive studies to fully understand the ecological significance and chemical complexity of BVOCs in benthic environments.

The genome of giant waterlily provides insights into the origin of angiosperms, leaf gigantism, and stamen function innovation

As some of the earliest evolving flowering plants, waterlilies offer unique insights into angiosperm evolution. Giant Amazonian waterlilies (genus Victoria) are of particular interest due to their production of the world's largest floating leaves and gigantic flowers that entrap pollinating beetles. Here, we report chromosome-level genome assemblies of Victoria cruziana and three related waterlilies: Euryale ferox, Nymphaea mexicana, and Brasenia schreberi. We found an ancient whole-genome duplication event specific to the Nymphaeales. We reveal major gene duplication and loss events throughout the evolution of angiosperms, with substantial implications for flower development and the biosynthesis of floral volatile organic compounds (FVOCs) in waterlilies. Importantly, we report a unique division of labor in the stamen function of V. cruziana linked to beetle attraction by FVOCs. This is related to the ultra-high expression of VicSABATHa along with Vicchitinase, possibly linked to protection from damage by trapped beetles. Overexpression of VicSABATHa in tobacco leaves reveals a capacity to produce volatile fatty acids, confirming its role in their catalytic synthesis. Overall, these findings provide novel insights into the evolution and adaptations of waterlilies and flowering plants in general.

Multidimensional analysis of the flavor characteristics of yellow peach at different ripening stages: Chemical composition profiling and sensory evaluation

The flavor evolution of yellow peaches during ripening was investigated using a gas chromatography-mass spectrometer (GC-MS), metabolomics, and electronic sensoristic techniques. Of the 41 volatiles quantified, 13 increased the intensity of the aroma based on the odor activity values (OAVs). Additionally, 142 non-volatile compounds were identified. Metabolic pathway analysis indicated that the formation of xanthophyll esters, due to substrate competition, resulted in a reduction of carotenoid-derived volatiles. Electronic nose (E-nose) analysis revealed that the key sensor W1C-associated volatiles had a green aroma, while W1S and W2S-associated volatiles showed a fruity aroma. Electronic tongue (E-tongue) analysis revealed that L-norleucine, L-isoleucine, isoleucine, L-tyrosine, L-valine, 4-Hydroxybenzaldehyde, cinnamic acid, and rutin positively correlated with umami and sweetness. Conversely, cis-aconitic acid and (-)-epigallocatechin positively correlated with sourness or astringency. Moreover, 20 volatiles, including γ-decalactone, linalool, and (Z)-3-hexenyl acetate, were positively correlated with umami or sweetness, while 7 volatiles were positively correlated with sourness or astringency.

Establishing a database of volatile metabolites in whole wheat (Triticum aestivum L.) flour provides novel insights into quality breeding

Improving yield traits is the primary goal for wheat breeding, while much less attention has been paid to flavor and odor quality of wheat grain. In this study, a high-throughput protocol was developed for the identification and quantification of volatile compounds (VOCs) in wheat grains via a static head-space coupled with GC-MS. Using a diverse population consisting of 312 wheat germplasms, a database including 94 VOCs was constructed for grains. The main pathways for the biosynthesis of VOCs in wheat grains was constructed by manually assigning the volatiles to the lipoxygenase, the mevalonic acid and the shikimate/phenylalanine pathway, respectively. VOC profiling showed that grain VOCs were mainly synthesized from the LOX pathway and the content of VOCs varied largely between different wheat lines. Clear discrimination was identified between old and modern cultivars by OPLS-DA, indicating a reduction of VOCs both in species and content in modern cultivars. Correlation analysis and machine learning models established a link between VOC profiles and grain protein content. VOCs such as 1-octen-3-ol were significantly correlated with grain protein content, which can be used as diagnostic markers for wheat grain quality. In summary, our study established a comprehensive VOC database for wheat grains and explored the relationships between VOCs and grain quality traits in a diverse wheat population, providing novel insights into grain quality improvement and flavor enhancement in modern breeding programs.

SlMES1 modulates methyl salicylate to influence fruit volatile profiles in tomato

Methyl salicylate (MeSA), known as phloem-based mobile signal, has been identified as undesirable volatile compounds for tomato fruits due to its medicinal and wintergreen aroma properties. However, the response of most volatile compounds to endogenous MeSA are still unclarified. In this work, we found the concentration of MeSA can be regulated by salicylic acid methyl esterase 1 (SlMES1). We used CRISPR/Cas9 and GC-MS strategies to investigate the effect of SlMES1 on the biosynthesis of flavor compounds during tomato fruit ripening. Our results showed that the loss of function of SlMES1 significantly increased the MeSA content by altering the flux of MeSA and SA interconversion. Although the increased endogenous MeSA did not affect the fruit ripening process, it altered the concentration and proportion of fruit volatiles, mainly reducing the concentration of soluble sugar and volatile substances derived from amino acids and carotenoids. Additionally, the reduction of soluble sugars and volatiles was associated with downregulated the gene encoding Sucrose synthase (SuSy), Alcohol dehydrogenase (ADH), Phenylalanine ammonia lyase (PAL), and β - Carotene hydroxylase (CHY-β) when compared with control. Taken together, SlMES1 plays a crucial role in regulating the MeSA content during fruit ripening and could become a breeding target for improving fruit flavor quality.

Current insights into plant volatile organic compound biosynthesis

Plant-derived volatile organic compounds (VOCs) are essential for various ecological interactions, including plant communication, pollinator attraction, and defense against herbivores. Some VOCs are active ingredients with significant economic and medicinal value. For example, monoterpenoids such as linalool, geraniol, menthol, camphor, borneol, citral, and thymol are well-known for their flavor and aroma. Most monoterpenoids have a strong scent and physiological activity; some compounds, like thymoquinone, have excellent anti-cancer activities, making them important for pharmaceuticals and also beneficial in food and cosmetics. VOCs encompass a diverse range of chemical classes, such as terpenoids, benzenoids/phenylpropanoids, amino acid derivatives, and fatty acid-derived compounds. With the development of genomic, transcriptomic, and metabolomic techniques, significant progress has been made in the discovery of genes for the biosynthesis of VOCs. Herein, recent advances in the biosynthesis of plant-derived VOCs, focusing on two main classes: benzenoids/phenylpropanoids and monoterpenes, are discussed. It highlights the identification of a peroxisomal enzyme, benzaldehyde synthase, in petunia that elucidates the biosynthetic pathway of benzaldehyde, and a bifunctional enzyme, geranyl/farnesyl diphosphate synthase (RcG/FPPS1), in roses (Rosa chinensis "Old Blush") that contributes to the production of cytosolic geranyl diphosphate. Current understanding about canonical and non-canonical pathways for monoterpene formation and some approaches that are useful for gene discovery have been discussed. Open questions and future perspectives in this field have also been presented.

Gas chromatography-ion mobility spectrometry-based fingerprint analysis of volatile flavor compounds in ginger cultivated under different conditions

Ginger is widely acclaimed for its pungent aroma, nutritional benefits, and unique pharmacological properties, making it essential in culinary and medicinal applications. This study investigates volatile flavor profile differences in ginger resulting from various cultivation practices. Gas chromatography-ion mobility spectrometry (GC-IMS) was utilized to isolate and identify volatile compounds. Subsequent analyses, including relative odor activity values (ROAV) and multivariate statistical analysis, precisely identified key flavor compounds differentiating organically cultivated ginger from conventional field-grown varieties. A total of fifty-six volatile compounds were identified, comprising 17 esters, 4 alcohols, 7 ketones, 18 terpenoids, 6 aldehydes, and 4 miscellaneous compounds, with esters and terpenoids constituting over 50 % of total volatiles. Compounds such as α-phellandrene, β-citronellal, butyl 2-propenoate, 2-heptanone-D, and 3-octanone predominantly contributed lemon, banana, and citronella notes in organically cultivated ginger. In contrast, citral dominated in conventional ginger. This research significantly advances our understanding of ginger's aroma under varied cultivation conditions and demonstrates GC-IMS's utility in effectively profiling ginger flavor, thereby guiding improved cultivation and management.

Unravel the molecular basis underlying inflorescence color variation in Macadamia based on widely targeted metabolomics

Macadamia integrifolia, a perennial evergreen crop valued for its nutritious nuts, also exhibits a diverse range of inflorescence colors that possess both ornamental and biological significance. Despite the economic importance of macadamia, the molecular mechanisms regulating flower coloration remain understudied. This study employed a combination of metabolomic and biochemical approaches to analyze metabolites present in inflorescences from 11 Macadamia cultivars, representing distinct color phenotypes. A total of 787 metabolites were identified through the use of ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), the majority of which were phenolic acids, flavonoids, and flavonols. Principal component analysis and clustering yielded a classification of the samples into three major flower color groups. The differential metabolites were found to be enriched in pathways such as flavonoid, flavonol, and phenylpropanoid biosynthesis, which have been demonstrated to be key contributors to color variation. Moreover, weighted gene co-expression network analysis (WGCNA) identified metabolite modules that were strongly associated with specific flower colors. This revealed that key compounds, including kaempferol, quercetin derivatives, and anthocyanins, were the primary drivers of pigmentation. This study provides a comprehensive framework for understanding the genetic, biochemical, and environmental factors influencing macadamia flower color. These findings contribute to the theoretical understanding of macadamia reproductive biology and have practical implications for molecular breeding, ornamental enhancement, and optimizing pollinator attraction to improve crop yield and ecological sustainability.

Chemical, morphological, and genetic characterization of the floral scent and scent-releasing structures of Gynandropsis gynandra (Cleomaceae, Brassicales)

Flowering plants showcase a remarkable diversity in floral fragrances, colours, and structures, which function harmoniously as signals to attract and guide pollinators. Like visual signals, the scents emitted by flowers can be associated with the attraction of specific pollinator classes. As such, divergence in floral scent composition can be a key isolation mechanism for speciation. Between continents, the leafy vegetable Gynandropsis gynandra possesses differences in morphology, phenology, foliar chemodiversity, and pollinators. Importantly, G. gynandra is pollinated by hawkmoths in Africa, and bees and butterflies in Asia. Here, we combined chemical, morphological, and transcriptome analyses to assess differences in the floral scent and scent-releasing structures between African and Asian G. gynandra accessions, and within flowers of the same accession. The prevalence of nitriles and benzenoids in the floral fragrance of the African and Asian accessions, respectively, corresponds to features typically associated with their differing pollinator classes. Further, we uncovered differences in floral epidermal cell morphology, with papillae present on the petal claws and nectary of the African accession and absent (or reduced) for the Asian accession. Through transcriptomic analyses, we showed that the stalk-like floral structures are putatively involved in terpenoid biosynthesis and emission. However, the epidermal cell morphology and staining suggests that the petals, stamens, and stigma may be involved in scent production of other floral volatile classes (e.g., nitrogen-containing compounds). These additional phytochemical and morphological distinctions between African and Asian accessions suggest that the divergent forms of G. gynandra may merit taxonomic recognition at subspecies level.

Analysis of changes in flavor characteristics of congou black tea at different fermentation degrees under industrial production conditions using flavor compound weighted network co-expression method

Fermentation is a key process in Congou black tea, but there is limited research on the changes in flavor factors and their interrelationships during different fermentation stages under industrial production. This study applies sensory evaluation and metabolomics techniques to explore the interactions between flavors. Sensory evaluation indicated that the 4-h fermented sample exhibited the best overall performance. The experiment of adding aroma substances further revealed the significant effects of sweet aroma and green odor on taste of sweetness and astringency. Additionally, 532 flavor compounds were identified using high-resolution liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. Moreover, significant differences were observed in the volatile compounds derived from flavonoids, amino acids, and fatty acids of samples with different fermentation degrees. Furthermore, weighted co-expression network analysis of flavor compounds showed that the oxidation of polyphenols, especially catechins, plays an important regulatory role in content changes of volatile and other non-volatile compounds during fermentation.

Analysis of the release pattern of floral aroma components of Rhus chinensis based on HS-SPME-GC-MS technique

Rhus chinensis, a native plant species of China, possesses significant economic value in the ornamental sector. This study investigates the floral fragrance components and release patterns of R. chinensis, thus providing a theoretical foundation for the utilization of its floral fragrance. Headspace-solid phase microextraction (HS-SPME), gas chromatography-mass spectrometry (GC-MS), and chemometrics were used in conjunction with principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) to identify the essential components of the floral aroma during the budding, blooming, and withering stages of R. chinensis. The important components of the aroma were also indicated by using the Variable Importance Projections (VIP) and Kruskal-Wallis nonparameters (P). The floral scent components of R. chinensis were abundant; 91 and 84 types of floral compounds were found throughout varying flowering seasons and daily patterns, respectively. The primary compounds responsible for flower odors were terpenes, representing over 70% of the floral aroma. Significant fluctuations were observed in the composition of 18 essential scent components and 21 chemicals, with daily variations observed in various flowering stages. The types of floral scent substances continued to rise during the flowering process; however, the relative concentrations of the floral aroma components of R. chinensis initially climbed and then fell, reaching 3.60μg/g at the full flowering stage and only 2.40μg/g after the withering stage. In the course of the daily shift, the release amount increased during the day compared to the night, peaking at 4.80μg/g. The substance type reached its greatest point at 12:00, making the circadian rhythm change rule evident. This study provides a reference for the further development and utilization of the flower fragrance of R. chinensis.

Multi-Omics and Physiological Analysis Reveal Crosstalk Between Aphid Resistance and Nitrogen Fertilization in Wheat

The availability of nitrogen (N) can dramatically influence crops resistance to herbivorous insects. However, the interaction between N fertilization and crop resistance to insects is not well understood. In this study, the effects of N fertilization on the grain aphid (Sitobion miscanthi) were investigated using three wheat (Triticum aestivum) cultivars with different aphid resistances. We measured aphid life cycle parameters, fecundity, survival rate, weight and feeding behavior, in conjunction with wheat metabolomics, transcriptomics and alien introgression analysis. Our results demonstrated that higher N application benefits aphid feeding across all three wheat cultivars. We also reveal that the highly resistant cultivar (ZM9) can only exert its resistance-advantage under low N fertilization, losing its advantage compared to moderately resistant cultivar YN19 and susceptible cultivar YN23 under higher N fertilization. The effects of N fertilization on wheat-aphid interactions were due to changes in the regulation of carbon and nitrogen metabolism. Integration of multi-omics highlighted specific aphid-induced differentially expressed genes (DEGs, e.g., TUB6, Tubulin 6; ENODL20, Early nodulin-like protein 20; ACT7 Actin 7; Prx47, Peroxidase 47) and significantly different metabolites (SDMs, e.g., crotonoside, guanine, 2'-O-methyladenosine, ferulic acid) in ZM9. Additionally, we report the unique SDMs-DEGs interactions, associated with introgression during wheat domestication, may help infer aphid resistance. In summary, this study provides new insights into the relationships between N fertilization practices, defense responses and integrated pest management for sustainable wheat production.

Metabolic insights of lactic acid bacteria in reducing off-flavors and antinutrients in plant-based fermented dairy alternatives

Multiple sensorial, technological, and nutritional challenges must be overcome when developing plant-based fermented dairy alternatives (PBFDA) to mimic their dairy counterparts. The elimination of plant-derived off-flavors (green, earthy, bitter, astringent) and the degradation of antinutrients are crucial quality factors highlighted by the industry for their effect on consumer acceptance. The adaptation of plant-derived lactic acid bacteria (LAB) species into plant niches is relevant when developing starter cultures for PBFDA products due to their evolutionary acquired ability to degrade plant-based undesirable compounds (off-flavors and antinutrients). Some plant-isolated species, such as Lactiplantibacillus plantarum and Limosilactobacillus fermentum, have been associated with the degradation of phytates, phenolic compounds, oxalates, and raffinose-family oligosaccharides (RFOs), whereas some animal-isolated species, such as Lactobacillus acidophilus strains, can metabolize phytates, RFOs, saponins, phenolic compounds, and oxalates. Some proteolytic LAB strains, such as Lacticaseibacillus paracasei and Lacticaseibacillus rhamnosus, have been characterized to degrade phytates, protease inhibitors, and oxalates. Other species have also been described regarding their abilities to biotransform phytic acid, RFOs, saponins, phenolic compounds, protease inhibitors, oxalates, and volatile off-flavor compounds (hexanal, nonanal, pentanal, and benzaldehyde). In addition, we performed a blast analysis considering antinutrient metabolic genes (42 genes) to up to 5 strains of all qualified presumption of safety-listed LAB species (55 species, 240 strains), finding out potential genotypical capabilities of LAB species that have not conventionally been used as starter cultures such as Lactiplantibacillus pentosus, Lactiplantibacillus paraplantarum, and Lactobacillus diolivorans for plant-based fermentations. This review provides a detailed understanding of genes and enzymes from LAB that target specific compounds in plant-based materials for plant-based fermented food applications.

Study on the damage and variation of Agropyron mongolicum induced by the combined action of discharge plasma and plasma-activated water

To investigate the effect of combined action of discharge plasma (DP) and plasma-activated water (PAW) in mutagenesis breeding, this study focuses on Agropyron mongolicum. We utilized high-voltage DC pulsed dielectric barrier discharge for seed treatment, alone and in combination with PAW. The research focused on germination rates, evolution of physicochemical properties of imbibition residual solution, reactive oxygen species (ROS), malondialdehyde (MDA), and volatile organic compounds (VOCs) to assess DP-induced damage and variability in Agropyron mongolicum. Results indicated that after 18 h of combined treatment, the germination rate of Agropyron mongolicum dropped to 29.67%, below the LD50 threshold. Treated seedlings exhibited elevated ROS and MDA levels compared to controls. The concentration of reactive nitrogen and oxygen species (RONS) in the imbibition residual solution of the combined treatment group was lower than in freshly prepared PAW, indicating RONS penetration into the seed embryo via water, leading to oxidative damage. Enhanced lateral root differentiation, early tillering, increased biomass, and albino variant plants were observed in the surviving seedlings post-treatment. Transmission electron microscope (TEM) and Gas Chromatography-Ion Mobility Spectrometry (GC-IMS) analysis confirmed that plasma treatment induced oxidative damage in Agropyron mongolicum. In conclusion, high-power, long-duration direct DP treatment caused oxidative damage and reduced germination rates in Agropyron mongolicum, with PAW intensifying these effects. PAW was identified as the main driver of variation and lethality, while DP played a supportive role. Combined DP and PAW treatment induced variations in Agropyron mongolicum, providing experimental evidence and theoretical insights for applying DP treatment in plant mutagenesis breeding.

Volatile profile of postharvest hardy kiwifruits treated with chitosan-silica nanocomposite coatings

Chitosan (CTS) is a natural polysaccharide derived from the deacetylation of chitin. Chitosan-based coatings are widely used for the preservation of hardy kiwifruits. However, the effect of chitosan-based coating on fruit flavor during ripening is rarely reported. In this study, the postharvest qualities of hardy kiwifruits were investigated using chitosan coating and chitosan-silica nanoparticle coating (CTS-SiNPs) during storage at 25°C and 4°C. Physicochemical analyses showed that chitosan coating extended the shelf-life by delaying ripening and maintaining higher quality than uncoated fruits, and CTS-SiNPs treatment showed a superior preservation effect compared to CTS treatment. Untargeted metabolomics analysis based on HS-SPME-GC-MS was used to comprehensively evaluate the volatile profiles of hardy kiwifruits during postharvest storage. The metabolomics analysis showed that two chitosan coating treatments greatly delayed the accumulation of most volatiles while delaying the ripening process, and the differential volatiles were mostly involved in the terpenoids biosynthesis pathway. Notably, most green leaf volatiles (C6/C9 aldehydes, esters and alcohols) and methyl salicylate were up-regulated in the CTS-SiNPs coating groups. In addition, odor activity value (OAV) was used to characterize the key aroma-active compounds and odor profiles. A total of 32 compounds were identified as key aroma-active compounds (OAV ≥ 1) in hardy kiwifruits. The odor profile evaluation showed that the CTS-SiNPs coating treatment enhanced the intensity of the "herbal" odor, while reducing the intensity of "sweet" and "floral" odors in hardy kiwifruits at the eating-ripe stage.

Plant secondary metabolites against biotic stresses for sustainable crop protection

Sustainable agriculture practices are indispensable for achieving a hunger-free world, especially as the global population continues to expand. Biotic stresses, such as pathogens, insects, and pests, severely threaten global food security and crop productivity. Traditional chemical pesticides, while effective, can lead to environmental degradation and increase pest resistance over time. Plant-derived natural products such as secondary metabolites like alkaloids, terpenoids, phenolics, and phytoalexins offer promising alternatives due to their ability to enhance plant immunity and inhibit pest activity. Recent advances in molecular biology and biotechnology have improved our understanding of how these natural compounds function at the cellular level, activating specific plant defense through complex biochemical pathways regulated by various transcription factors (TFs) such as MYB, WRKY, bHLH, bZIP, NAC, and AP2/ERF. Advancements in multi-omics approaches, including genomics, transcriptomics, proteomics, and metabolomics, have significantly improved the understanding of the regulatory networks that govern PSM synthesis. These integrative approaches have led to the discovery of novel insights into plant responses to biotic stresses, identifying key regulatory genes and pathways involved in plant defense. Advanced technologies like CRISPR/Cas9-mediated gene editing allow precise manipulation of PSM pathways, further enhancing plant resistance. Understanding the complex interaction between PSMs, TFs, and biotic stress responses not only advances our knowledge of plant biology but also provides feasible strategies for developing crops with improved resistance to pests and diseases, contributing to sustainable agriculture and food security. This review emphasizes the crucial role of PSMs, their biosynthetic pathways, the regulatory influence of TFs, and their potential applications in enhancing plant defense and sustainability. It also highlights the astounding potential of multi-omics approaches to discover gene functions and the metabolic engineering of genes associated with secondary metabolite biosynthesis. Taken together, this review provides new insights into research opportunities for enhancing biotic stress tolerance in crops through utilizing plant secondary metabolites.

What Do We Know About Capsicum Volatilome?

The Capsicum genus includes several cultivated species that release complex blends of volatile organic compounds (VOCs) associated with their unique aroma. These VOCs are essential info-chemicals in ecological interactions. In this review, we describe how the volatilomic profiling naturally varies based on specific plant organs and genotypes as well as how non-beneficial organisms affect VOCs biosynthesis and accumulation in pepper plants. Also, we show evidence about VOCs variation under the pressure of different abiotic factors such as water stress, soil type and nutrient availability. The contribution of specific metabolic pathways and gene expression related to the biosynthesis of particular VOCs is addressed. We highlighted the utility of VOCs as chemical markers for quality control in the food industry, breeding programs to generate resistant plants and to improve aroma innovation. Herein we present a database containing 2734 VOCs, revealing 113 as the basic core of the volatilome from five Capsicum species.

Manipulating stomatal aperture by silencing StSLAC1 affects potato plant-herbivore-parasitoid tritrophic interactions under drought stress

The effects of drought stress on stomatal opening dynamics, plant volatile organic compound (VOC) emissions and plant-insect interactions have been well-documented individually, but how they interact mechanistically remains poorly studied. Here, we studied how drought-triggered stomatal closure affects VOC emission and plant-trophic interactions by combining RNAi silencing, molecular biological and chemical analyses (GC-MS) of a potato-tuber moth-egg parasitoid tritrophic system. Drought stress attenuated stomatal apertures and VOC emissions, which made the potato (Solanum tuberosum L.) plants more attractive to the herbivore but less attractive to the parasitoid. Stomatal aperture manipulations through StSLAC1 gene knockdown and chemical treatments (ABA and 5-aminolevulinic acid) consistently affected drought-triggered VOC emissions and plant-herbivore-parasitoid interactions, supporting aperture-dependent VOC emission. RNA-Seq analysis revealed that drought stress did not transcriptionally inhibit VOC biosynthesis. Collectively, our findings are consistent with the stomatal regulation of plant-insect interactions through the modulation of VOC emissions under drought stress. This highlights the intricate interplay between stomatal dynamics, VOC emission and plant-insect interactions.

Differential gene expression and metabolic pathways in Toona sinensis: Influence on colour and aroma

Toona sinensis, a plant species renowned for its culinary and medicinal properties, exhibits diverse colour variations that contribute to its aesthetic appeal and commercial value. Understanding the molecular mechanisms underlying colour and aroma traits in Toona sinensis is crucial for breeding programs and quality regulation in agriculture and the food industry. The present investigation included a comprehensive analysis of the transcriptomic and metabolomic profiles of Toona sinensis with different colours, including green, red, and red leaves with green stems. Metabolic analysis revealed that the flavonoid biosynthesis pathway governs the colour distinction between green and red Toona sinensis. The top 10 metabolites influenced by transcriptome include terpenoids (5), heterocyclic compounds (1), phenol (1), ketone (1), aldehyde (1), and alcohol (1). Fifteen highly expressed genes impacted by phenylpropanoid, sesquiterpenoid, and triterpenoid biosynthesis in coloured Toona sinensis. Functional annotation and pathway analysis revealed that terpene metabolites are predominantly synthesized via terpene metabolic pathway, involving eight key gene families. This study underscores the importance of multi-omics approaches in unravelling the genetic and metabolic basis of phenotypic traits in plant species aimed at improving colour, aroma, and nutritional quality in plants and derived products. HIGHLIGHTS: Flavonoid biosynthesis pathway governs the colour distinction between green and red Toona sinensis. The top 10 metabolites influenced by transcriptome include five terpenoids, one heterocyclic compound, one phenol, one ketone, one aldehyde, and one alcohol. Fifteen highly expressed genes impacted by phenylpropanoid, sesquiterpenoid, and triterpenoid biosynthesis in coloured Toona sinensis. Terpene metabolites are predominantly synthesized via the terpene metabolic pathway, involving eight key gene families. The net photosynthetic rate and intercellular CO2 concentration are relatively high in the red Toon sinensis morph.

Untargeted flower volatilome profiling highlights differential pollinator attraction strategies in muscadine

Floral aromas are a mixture of volatile organic compounds, essential attributes associated with the attraction of different pollinators. This investigation is the first in-depth exploration of the volatile profiles of sixteen muscadine grape genotypes, producing female and perfect flowers using the headspace solid-phase microextraction (HS-SPME)-GC-MS-based untargeted volatilomics approach. A total of one hundred fifty volatile metabolites were identified in the muscadine flower genotypes, including the functional groups of hydrocarbons, esters, alcohols, ketones, aldehydes, miscellaneous, and acids. Multivariate statistical analysis for volatile terpenes revealed eleven bio-marker terpene volatiles that primarily distinguish between female and perfect flowers. The β-elemene, β-bisabolene, and α-muurolene were the marker volatiles characterizing perfect flowers; however, α-selinene, (Z,E)-α-farnesene, and (E,E)-geranyl linalool were the typical marker terpene in the female flowers. Perfect flowers exhibited better pollinator attraction capacity associated with a higher number of flowers per inflorescence, enhanced pollinator rewards, and higher numbers and quantities of terpene volatiles than female flowers, resulting in superior pollinator attraction capacity and fruit set efficiency. The pollinator attraction mechanism of female flowers exhibited several morphological and biochemical floral defects, causing random pollinator visits and low fruit set efficiency. The controlled pollination assay could express female flowers' full fruit set capabilities by avoiding casual insect pollination. This comprehensive study suggests that these marker terpenes might contribute to pollinator attraction in muscadine flower genotypes and should be considered an excellent reference for agroecosystem ecologists and entomologists.

Phylogeny and Functional Differentiation of the Terpene Synthase Gene Family in Angiosperms with Emphasis on Rosa chinensis

Terpenes are pivotal for plant growth, development, and adaptation to environmental stresses. With the advent of extensive genomic data and sophisticated bioinformatics tools, new insights into the evolutionary dynamics and functional diversification of terpene synthases (TPSs) have emerged. Despite genome-wide identifications of the TPS family in certain species, comprehensive cross-species analyses remain scarce. In this study, we conducted a genome-wide identification and subgroup classification of TPS families across 115 angiosperms with available genomic sequences. Our phylogenomic synteny network analysis elucidated the complex evolutionary history of TPS genes, revealing notable expansions and contractions among subgroups. Specifically, TPS-a showed significant expansion, while TPS-b was variably lost in some Poaceae, indicating adaptive responses. TPS-c maintained considerable conservation across species, whereas TPS-e/f diverged into distinct evolutionary trajectories despite functional overlap, with TPS-e further splitting into two angiosperm-specific clades. The TPS-g subgroup displayed lineage-restricted distribution, primarily in super-rosids and monocots. Notably, TPS-d and TPS-h subgroups were absent in angiosperms. Employing Rosa chinensis as a case study, we identified RcTPS23, a conserved bifunctional terpene synthase, highlighting the utility of cross-species synteny data in functional prediction. This comprehensive analysis elucidates the phylogenetic and functional landscape of TPS subgroups in angiosperms, providing a robust framework for predicting TPS function and guiding further functional investigations.

Analysis of Differences in Volatile Components of Rucheng Baimao (Camellia pubescens) Black Tea in Different Seasons

At present, there are few studies on seasonal differences in the aroma quality and volatile components of Rucheng Baimao (Camellia pubescens) black tea. In this study, sensory evaluation and volatile component analysis were carried out on one sample of Rucheng Baimao black tea corresponding to spring, summer, and autumn, respectively. The results of sensory evaluation showed that the black teas of all three seasons had floral aromas. However, the aroma quality of spring black tea was the best, followed by that of autumn black tea, and summer black tea was the worst. The analysis of volatile components showed that alcohols, esters, and alkanes were the main substance categories. In addition, the results of the aroma index were consistent with those of the sensory evaluation, indicating that spring black tea had the best aroma quality, followed by autumn black tea and then summer black tea. Eleven key differential volatile components were screened by combining PLS-DA analysis (VIP > 1, p < 0.05) and rOAV > 1. Among them, geraniol, methyl salicylate, nonanal, and (E)-citral accumulated the most in spring black tea, linalool, phenylacetaldehyde, benzaldehyde, phenethyl alcohol, benzyl alcohol, and β-ionone accumulated the most in summer black tea, and trans-nerolidol accumulated the most in autumn black tea. This study aims to provide a theoretical reference for the regulation of the aroma quality of Rucheng Baimao black tea.

Why do we like so much the smell of roses: The recipe for the perfect flower

The rose is the most cultivated ornamental plant in the world, and one of the reasons is that its fragrance is highly pleasant to humans. This raises the question of which volatile organic compounds (VOCs) emitted by flowers are involved in a rose odor-induced positive emotional response. Here, we invited participants to smell and rate the perceptual characteristics of roses whose VOCs were quantified. We revealed that (1) the more rose-specific the flower perception, the more pleasant the smell and (2) the rosy perception is driven by ionones and to a lesser extent by oxylipins while pleasantness by balanced proportion in the mixture of ionones, oxylipins, and 2-phenylethanol and derivatives. In the mixture, the proportion of some compounds, such as aliphatics and phenolic methyl esters, impact negatively the rose scent. Thus, the pleasure that roses bring to humans could be explained by the non-conscious perception of this unique mixture of compounds.

Integrative transcriptome and metabolome analysis reveals candidate genes related to terpene synthesis in Chrysanthemum × morifolium

BACKGROUND

Chrysanthemum (Chrysanthemum × morifolium) is one of the four major cut flowers worldwide and is valued for ornamental, culinary, and medicinal purposes. Terpenoids are key components of the fragrance of chrysanthemum; they not only serve to repel insect herbivores and promote pollination but also impact the value of the plant. However, the terpene production of chrysanthemum and the regulatory mechanisms involved remain unclear.

RESULTS

We used gas chromatography‒mass spectrometry (GC‒MS) to identify 177 compounds, including 106 terpenes, in ten chrysanthemum cultivars. Monoterpene derivatives and sesquiterpenes were the most common. Next, we identified 27 candidate hub genes for terpene production in chrysanthemum via combined transcriptome and metabolome analysis, as well as weighted gene coexpression network analysis. The three terpenes synthesis-related genes were significantly expressed in the disc florets of the different chrysanthemum cultivars. We concluded that the transcription factors TCP8, TCP5, ATHB8, ATHB7, HAT22, TGA1, TGA4, and WHY1 may regulate terpene synthesis.

CONCLUSIONS

In this study, we profiled terpenes in chrysanthemum florets and constructed a key terpene-transcription factor network related to terpene synthesis. These findings lay the groundwork for future research into the mechanism of terpene synthesis in chrysanthemum as well as in other plants.

Host plants selection of Centranthera grandiflora Benth. and nontargeted metabolomics analysis of its parasitic and non-parasitic samples

According to the previous investigation and research of our group, it was found that Centranthera grandiflora Benth. (C. grandiflora for short) might be a root hemiparasitic plant. The experiments of mixed sowing of C. grandiflora and 9 companion plants that might be hosts were conducted, and the growth, biological yield and other indexes were observed. The results showed that Cyperus iria L. was the best host for C. grandiflora, and when they were mixed sowed, C. grandiflora had a vigorous growth above ground and the haustoria connected obviously below ground, while C. grandiflora could achieve blossoming and fruiting in the same year. Next, nontargeted metabonomics analysis methods were utilized to clarify the differences in metabolites between parasitized and non-parasitized C. grandiflora. A total of 82 metabolites with significant differences were screened. The main upregulated differential metabolites of non-parasitized plants were for plant growth, while that of parasitized plants were functional compounds such as EPA. Out of 82 differential metabolites, 32 were annotated into 37 KEGG pathways. Analysis of the 37 pathways in combination with the differential metabolites showed that in addition to being involved in the synthesis pathway of iridoid terpenes, the up-regulated metabolites of parasitized plants were involved in the synthesis pathways of several functional components, while that of non-parasitic plants were involved in the subsequent catabolism of monoterpenoid compounds, as well as the metabolic pathways of nutrients synthesis and catabolism, energy generation, and phytohormone production required for plant growth.

Genome-Wide Characterization of Differentially Expressed Scent Genes in the MEP Control Network of the Flower of Lilium 'Sorbonne'

Fragrance is an important feature of ornamental lilies. Components of volatile substances and important genes for monoterpene synthesis in the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway were examined in this study. Twenty volatile compounds (2 in the budding stage, 3 in the initial flowering stage, 7 in the semi-flowering stage, 17 in the full-flowering stage, and 5 in withering stage) were detected in the Oriental lily 'Sorbonne' using gas chromatography-mass spectrometry. The semi- and full-flowering stages were key periods for volatile substance production and enzyme function. Sequence assembly from samples collected during all flowering stages resulted in the detection of 274,849 genes and 129,017 transcripts. RNA sequencing and heatmapping led to the detection of genes in the MEP monoterpene metabolism pathway. Through gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis, we extracted key genes (LiDXS2, LiLIS, and LiMYS) and transcription factors (in the bHLH, MYB, HD-ZIP, and NAC families) associated with the MEP pathway. Tissue localization revealed that LiDXS2, LiLIS, and LiMYS were expressed in Lilium 'Sorbonne' petals in the full-flowering stage. Genes regulating the 1-deoxy-D-X-lignone-5-phosphate synthase family of rate-limiting enzymes, involved in the first step of monoterpene synthesis, showed high expression in the semi- and full-flowering stages. LiDXS2 was cloned and localized in chloroplast subcells. The relative expression of terpene-related genes in the MEP and mevalonic acid pathways of wild-type and LiLIS/LiMYS transgenic Arabidopsis thaliana, and changes in chemical composition, confirmed that LiLIS/LiMYS regulates the monoterpene synthesis pathway. The results of this study provide a theoretical basis for the synthesis of lily aromatic substances and the cultivation of new garden flower varieties.

Revealing the roles of solar withering and shaking processes on oolong tea manufacturing from transcriptome and volatile profile analysis

Solar and indoor withering in the manufacturing process of semi-fermented oolong tea are crucial for aroma formation. While the processes have been established through accumulated experience, the underlying mechanisms remain largely unknown. This study identified pairs of gene and volatile organic compound (VOC) that were significantly correlated and up-regulated during solar withering and the first shaking, including lipoxygenase 8 (LOX8) with 3-hexenyl iso-butyrate, terpene synthase 2 (TPS2) with β-ocimene and linalool, as well as tryptophan synthase β-subunit 2 (TSB2) with indole. Besides, two β-glucosidases (β-GH), β-GH1_1 and β-GH3_1, were up-regulated by more than 30-fold in these stages. When comparing the three manufacturing procedures, indole, nerolidol, β-ocimene, benzyl nitrile, and jasmine lactone, were largely accumulated only in the normal process, where both solar withering and shaking were included. These findings provide insights into the regulation of VOC accumulation under stresses during withering, and highlight the importance of specific manufacturing processes in the formation of oolong tea characteristic aroma.

Treasures Induced by Narrow-Spectrum: Volatile Phenylpropanoid and Terpene Compounds in Leaves of Lemon Basil (Ocimum × citriodorum Vis.), Sweet Basil (O. basilicum L.) and Bush Basil (O. minimum L.) Under Artificial Light City Farm Conditions

The cultivation of aromatic plants that are valuable for nutritional and medical aims under artificial conditions with narrow-band LED lighting is becoming widespread. A comparison of the effects of conventional basil field and greenhouse conditions and a city farm (CF) with LED lighting on essential oil and its components was studied in Ocimum × citriodorum Vis. "Kapriz" (OcK), O. basilicum L. "Queen Sheba" (ObQS) and O. minimum L. "Vasilisk" (OmV). Essential oil (EO) was extracted by hydrodistillation from dry leaves of the basil varieties. EO composition was studied by gas chromatography, while the number of glandular trichomes was studied by scanning electron microscopy. We found that in leaves of CF plants, ObQS and OmV increased EO yield (22.9 and 22.7 g/kg DW, respectively) compared to field conditions (10.9 and 13.7 g/kg DW, respectively). The number of glands with four-celled heads also increased. In OcK plants, the amount of EO was almost unchanged, but the number of capitate glandular trichomes was strongly increased. Biochemical analysis showed that in CF plants compared to field ones, eugenol accumulated 40% more in ObQS and three times more in OmV. In addition, 10.9% estragol was detected in the leaves of OcK plants, which was absent in field plants. Thus, LED lighting conditions increased the biosynthesis of phenylpropanoid volatile components in Ocimum.

Impact of a Novel Two-Phase Natural Deep Eutectic Solvent-Assisted Extraction on the Structural, Functional, and Flavor Properties of Hemp Protein Isolates

Defatting dehulled hemp seeds is a crucial step prior to protein extraction. However, conventional methods rely on flammable solvents, posing significant health, safety, and environmental concerns. Additionally, hemp protein has poor extractability, challenging functionality, and flavor limitations, restricting its broader application in foods. Accordingly, a two-phase natural deep eutectic solvent (NADES)-assisted extraction was evaluated as a solvent-free alternative for co-extracting protein and oil from full-fat hemp flour. In comparison to the reference hemp protein isolate (R-HPI), produced from hexane-defatted flour following conventional alkaline extraction, NADES-extracted hemp protein isolate (N-HPI) had significantly higher protein extraction yield and purity. N-HPI exhibited enhanced surface charge, lower hydrophobicity, and thus higher solubility at an acidic pH compared to R-HPI. N-HPI had a higher abundance of edestin and lower levels of vicilin-like proteins, which contributed to superior gelation compared to R-HPI. N-HPI, compared to R-HPI, contained lower levels of lipid-derived off-flavor compounds, such as aldehydes, alcohols, and ketones. These findings highlighted, for the first time, the potential of a two-phase NADES-assisted extraction as a sustainable alternate and effective process for producing high-quality, functional hemp protein. The development of such a green process is an impetus for broadening the applications of hemp protein in food systems.

Comparative analysis of petal phytoconstituents reveals insights into the characteristics of an under-reported edible old rose variety native to Chongqing, China

Chongqing Old Rose is an ancient edible rose variety native to Chongqing, China, but is under-reported. Further evidence is required to fully establish its potential benefits. The complete metabolic profiles were examined for comparative analysis between the Old Rose and three rose cultivars. The results showed that the pathways of flavonoid biosynthesis, monoterpenoid biosynthesis, and phenylalanine metabolism were significantly enriched in Old Rose. The predominant anthocyanins in Old Rose were cyanidin and peonidin, which may contribute to flower coloration and indicate the antioxidant potential of this plant. Additionally, this plant was rich in aromatic compounds and terpenoids such as 2-phenylethanol, linalool, geraniol, and caryophyllene α-oxide, indicating that it has a natural basis for extracting essential oil. Moreover, the presence of some active phytoconstituents, such as phenols, steroids, and alkaloids, also suggests its potential for edible and medicinal applications besides flavonoids and terpenoids.

Uncovering the effects of spreading under different light irradiation on the volatile and non-volatile metabolites of green tea by intelligent sensory technologies integrated with targeted and non-targeted metabolomics analyses

Spreading serves as a pivotal process in the flavor development of green tea. In this study, the effects of spreading under five light irradiation on the volatile and non-volatile metabolites of green tea were comprehensively investigated using intelligent sensory technologies integrated with targeted and non-targeted metabolomics analyses. The incorporation of yellow light irradiation into spreading process significantly improved the overall quality of green tea. A total of 71 volatile and 112 non-volatile metabolites were identified by GC-MS/MS and UHPLC-Q-Exactive/MS, respectively. Among them, 20 key odorants with OAVs exceeding 1 were screened out. Moreover, phenylethyl alcohol, β-damascenone, β-ionone, (E, Z)-2,6-nonadienal, linalool, and phenylacetaldehyde with higher OAVs were pivotal contributors to the aroma quality under different light irradiation. Additionally, 13 non-volatile metabolites with VIP > 1.2 were recognized as key differential metabolites under different light irradiation. The results provide technical support and theoretical guidance for enhancing the processing technology of green tea.

Extreme smells-microbial production of volatile organic compounds at the limits of life

Microbial volatile organic compounds (MVOCs) are diverse molecules produced by microorganisms, ranging from mere waste byproducts to important signalling molecules. While the interest in MVOCs has been increasing steadily, there is a significant gap in our knowledge of MVOCs in extreme environments with e.g. extreme temperatures or acidity. Microorganisms in these conditions are subjected to additional stress compared to their counterparts in moderate environments and in many cases have evolved unique adaptations, including the production of specialized MVOCs. This review highlights the diversity of MVOCs identified in extreme environments or produced by isolated extremophiles. Furthermore, we explore potential applications already investigated and discuss broader implications for biotechnology, environmental biology, and astrobiology.

Classification of Strawberry Maturity Stages and Varieties Using Neural Networks Based on Volatile Organic Compounds

Volatile organic compounds (VOCs) are closely associated with the maturity and variety of strawberries. However, the complexity of VOCs hinders their potential application in strawberry classification. This study developed a novel classification workflow using strawberry VOC profiles and machine learning (ML) models for precise fruit classification. A comprehensive VOC dataset was rapidly collected using gas chromatography-ion mobility spectrometry (GC-IMS) from five strawberry varieties at four maturity stages (n = 300) and visualized through principal component analysis (PCA). Five ML models were developed, including partial least squares discriminant analysis (PLS-DA), decision trees, support vector machines (SVM), Xgboost and neural networks (NN). The accuracy of all models ranged from 90.00% to 98.33%, with the NN model demonstrating the best performance. Specifically, it achieved 96.67% accuracy for single-maturity classification, 98.33% for single-variety classification, and 96.67% for dual maturity and variety classification, along with 98.09% precision, 97.92% recall, and 97.91% F1 score. Feature importance analysis indicated that the NN model exhibited the most balanced reliance on various VOCs, contributing to its optimal performance with the broad-spectrum VOC detection method, GC-IMS. Overall, these findings underscore the potential of NN modeling for accurate and efficient fruit classification based on integrated VOC profiles.

The Scent of Lily Flowers: Advances in the Identification, Biosynthesis, and Regulation of Fragrance Components

Lilies (Lilium spp.) are renowned for their diverse and captivating floral scents, which are highly valued both commercially and ornamentally. This review provides a comprehensive overview of recent advancements in the identification, biosynthesis, and regulation of fragrance components in lily flowers. Various volatile organic compounds (VOCs) that contribute to the unique scents of different lily species and cultivars, including terpenoids, benzenoids/phenylpropanoids, and fatty acid derivatives, are discussed. The release patterns of these compounds from different floral tissues and at different developmental stages are examined, highlighting the significant role of tepals. Detection methods such as gas chromatography-mass spectrometry (GC-MS) and sensory analysis are evaluated for their effectiveness in fragrance research. Additionally, the biosynthetic pathways of key fragrance compounds are explored, focusing on the terpenoid and benzenoid/phenylpropanoid pathways and the regulatory mechanisms involving transcription factors and environmental factors. This review also addresses the influence of genetic and environmental factors on fragrance production and proposes future research directions to enhance the aromatic qualities of lilies through selective genetic and breeding approaches. Emphasis is placed on the potential applications of these findings in the floral industry to improve the commercial value and consumer appeal of lily flowers.

Optimal seasonal schedule for producing biogenic volatile organic compounds for tree defense

The leaves of many trees emit biogenic volatile organic compounds (BVOCs) that protect them from various threats, including herbivory, pathogens, and heat stress. In a previous study, we analyzed the optimal seasonal schedule for producing isoprene, a highly volatile BVOC, in leaves to mitigate heat damage and maximize net carbon gain. In this paper, we investigate the seasonal production schedule of BVOCs stored in leaves, such as monoterpenes and sesquiterpenes, which decay slowly. When the leaves are bitten, these chemicals are emitted and help to prevent further herbivory. The optimal seasonal schedule, analyzed using Pontryagin's maximum principle, includes a period of singular control. Producing BVOCs for defense is advantageous if their decay rate is slow and the photosynthetic rate is fast. The amount of BVOCs produced increases with slower decay rate and faster photosynthetic rate. But it does not increase monotonically with the magnitude of the threat. BVOCs are produced earlier than the peak period of the threat for which the chemicals are intended. Based on the results of the model, we discuss the reported variations in BVOC production among different chemical species and tree species, as well as the seasonal patterns of gene expression in different pathways for BVOC production.

Expression Analysis and Functional Validation of DcTPSb1 in Terpene Synthesis of Dendrobium chrysotoxum

Terpenes are critical components of the floral fragrance component in Dendrobium chrysotoxum, synthesized by terpene synthase (TPS). Analysis of the D. chrysotoxum genome and transcriptional data revealed that the gene DcTPSb1 was significantly up-regulated during flowering periods, showing a strong correlation with the accumulation of aromatic monoterpenes in the floral components of Dendrobium chrysotoxum. Consequently, the DcTPSb1 gene was selected for further analysis. DcTPSb1 exhibited elevated expression levels in flowers among four organs (roots, stems, leaves, flowers) of D. chrysotoxum, with the highest expression observed during the blooming phase, which aligned with the accumulation of volatile terpenes during flowering. DcTPSb1, located in the chloroplasts, was identified as a member of the TPS-b subfamily associated with monoterpenes synthesis, showing close phylogenetic relationships with homologous proteins in related plant species. An analysis of the promoter region of DcTPSb1 indicated that it may be regulated by methyl jasmonate (MeJA) responsiveness. Functionally, DcTPSb1 was shown to catalyze the conversion of geranyl diphosphate (GPP) to linalool, ocimene, and (-)-α-pinitol in vitro. Overexpression of DcTPSb1 in tobacco resulted in a significant increase in terpenoid release during the blooming stage; however, the up-regulated substances did not include their catalytic products. The classification of DcTPSb1 as a terpene synthase capable of producing multiple products provides valuable insights into the complex biosynthesis of terpenes in orchids. These findings enhance our understanding of the functional diversity of DcTPSb1 and the processes involved in terpene biosynthesis in orchids.