Reducing nitrate and tobacco‐specific nitrosamine level in burley tobacco leaves through grafting on flue‐cured tobacco rootstock
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ABSTRACT:
SUBMITTER: Feng Y
PROVIDER: S-EPMC10568975 | biostudies-literature | 2023 Oct
REPOSITORIES: biostudies-literature
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Project description:Burley tobacco is a genotype of chloroplast-deficient mutant with accumulates high levels of tobacco-specific nitrosamines (TSNAs) which would induce malignant tumors in animals. Nitrate is a principle precursor of tobacco-specific nitrosamines. Nitrate content in burley tobacco was significantly higher than that in flue-cured tobacco. The present study investigated differences between the two tobacco types to explore the mechanisms of nitrate accumulation in burley tobacco. transcripts (3079) related to the nitrogen and carbon metabolism were observed. Expression of genes involved in carbon fixation, glucose and starch biosynthesis, nitrate translocation and assimilation were significantly low in burley tobacco than flue-cured tobacco. Being relative to flue-cured tobacco, burley tobacco was significantly lower at total nitrogen and carbohydrate content, nitrate reductase and glutamine synthetase activities, chlorophyll content and photosynthetic rate (Pn), but higher nitrate content. Burley tobacco required six-fold more nitrogen fertilizers than flue-cured tobacco, but both tobaccos had a similar leaf biomass. Reduced chlorophyll content and photosynthetic rate (Pn) might result in low carbohydrate formation, and low capacity of nitrogen assimilation and translocation might lead to nitrate accumulation in burley tobacco.
| S-EPMC6149767 | biostudies-literature
Project description:Burley tobaccos (Nicotiana tabacum) display a nitrogen-use-deficiency phenotype that is associated with the accumulation of high levels of nitrate within the leaf, a trait correlated with production of a class of compounds referred to as tobacco-specific nitrosamines (TSNAs). Two TSNA species, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN), have been shown to be strong carcinogens in numerous animal studies. We investigated the potential of molecular genetic strategies to lower nitrate levels in burley tobaccos by overexpressing genes encoding key enzymes of the nitrogen-assimilation pathway. Of the various constructs tested, only the expression of a constitutively active nitrate reductase (NR) dramatically decreased free nitrate levels in the leaves. Field-grown tobacco plants expressing this NR variant exhibited greatly reduced levels of TSNAs in both cured leaves and mainstream smoke of cigarettes made from these materials. Decreasing leaf nitrate levels via expression of a constitutively active NR enzyme represents an exceptionally promising means for reducing the production of NNN and NNK, two of the most well-documented animal carcinogens found in tobacco products.
| S-EPMC5066804 | biostudies-literature
Project description:Up to now, the mechanism of the effect of topping on tobacco hormone regulation is not clear, and most studies on plant hormone signal transduction pathways rely on gene or transcriptional pathways. In this study, the regulatory mechanism of hormones in roots and leaves of topped and untopped tobacco was studied at the protein level.
2023-10-19 | PXD043495 | Pride
Project description:Starch is an essential factor affecting the quality of flue-cured tobacco, and high starch content can affect the sensory quality and safety. Recently, the degradation of macromolecules in tobacco raw materials by using additional microorganisms to improve their intrinsic quality and safety has become a new research hotspot in the tobacco industry. However, the technical maturity and application scale are limited. Our study analyzed the correlation between microbial community composition and volatile components on the surface of tobacco leaves from 14 different grades in Fujian tobacco-producing areas. The PICRUSt software was utilized to predict the function of the microbial community present in tobacco leaves. Furthermore, dominant strains that produced amylase were screened out, and an enzyme solution was prepared to enhance the flue-cured tobacco flavor. Changes in the content of macromolecules and volatile components were determined, and sensory evaluations were conducted to assess the overall quality of the tobacco leaves. The results showed that the dominant bacterial genera on the surface of Fujian tobacco leaves were Variovorax, Sphingomonas, Bacillus, etc. Bacillus was positively correlated with various volatile components, which contributed to the sweet and aromatic flavors of Fujian flue-cured tobacco. The main genetic functions of Fujian flue-cured tobacco surface bacteria were carbohydrate metabolism and amino acid metabolism. After treating flue-cured tobacco with an enzyme preparation prepared by the fermentation of Paenibacillus amylolyticus A17 #, the content of starch, pectin, and cellulose in flue-cured tobacco decreased significantly compared with the control group. Meanwhile, the content of total soluble sugar and reducing sugar was significantly increased, and the volatile aroma components, such as 3-hydroxy--damascone, 2,3-dihydro-3,5-dihydroxy-6-methyl-4 H-Pyran-4-one, ethyl palmitate, ethyl linolenic acid, etc., were significantly increased. The aroma quality and quantity of flue-cured tobacco were enhanced, while impurities were reduced. The smoke characteristics were improved, with increased fineness, concentration, and moderate strength. The taste characteristics were also improved, with reduced irritation and a better aftertaste. In conclusion, Bacillus, as the dominant genus in the abundance of bacterial communities on tobacco surfaces in Fujian, had an essential impact on the flavor of tobacco leaves by participating in carbohydrate metabolism and finally forming the unique flavor style of flue-cured tobacco in Fujian tobacco-producing areas. Paenibacillus amylolyticus A17 #, a target strain with amylase-producing ability, was screened from the surface of Fujian flue-cured tobacco. The enzyme preparation, produced by the fermentation of Paenibacillus amylolyticus A17 #, was utilized to reduce the content of macromolecules, increase the content of water-soluble total sugar and reducing sugar, and produce a variety of crucial volatile aroma components, which had a significant improvement on the quality of tobacco leaves.
| S-EPMC10335769 | biostudies-literature
Project description:BackgroundContinuous cropping of the same crop leads to land degradation. This is also called the continuous-cropping obstacle. Currently, intercropping tobacco with other crops can serve as an effective strategy to alleviate continuous cropping obstacles.ResultsIn this study, tobacco K326 and insectary floral plants were used as materials, and seven treatments of tobacco monoculture (CK), tobacco intercropped with Tagetes erecta, Vicia villosa, Fagopyrum esculentum, Lobularia maritima, Trifolium repens, and Argyranthemum frutescens respectively, were set up to study their effects on rhizosphere soil chemical properties and composition and structure of rhizosphere soil microbial community of tobacco. The 16 S rRNA gene and ITS amplicons were sequenced using Illumina high-throughput sequencing. tobacco/insectary floral plants intercropping can influence rhizosphere soil chemical properties, which also change rhizosphere microbial communities. The CK and treatment groups tobacco rhizosphere soil microorganisms had significantly different genera, such as tobacco intercropping with T. repens and A. frutescens significantly increased the number of Fusarium and intercropping T. erecta, V. villosa, L. maritima, T. repens, and A. frutescens significantly increased the number of Sphingomonas and unknown Gemmatimonadaceae. Additionally, intercropping T. erecta, V. villosa and L. maritima changed the rhizosphere fungal and bacteria community and composition of tobacco and the positive correlation between tobacco rhizosphere the genera of fungi and bacterial were greater than CK. The pathway of the carbohydrate metabolism, amino acid metabolism, and energy metabolism in rhizosphere bacteria were significantly decreased after continuous cropping. Fungal symbiotic trophic and saprophytic trophic were significantly increased after intercropping V. villosa, L. maritima and plant pathogen and animal pathogen were increased after intercropping T. repens and A. frutescens. Additionally, bacterial and fungal communities significantly correlated with soil chemical properties, respectively.ConclusionThis study reveals that intercropping tobacco with insectary floral plants, particularly T. erecta, V. villosa, L. maritima and A. frutescens significantly affects soil chemical properties and alters rhizosphere microbial communities, increasing the abundance of certain microbial genera. Additionally, intercropping enhances pathways related to carbohydrate, amino acid, and energy metabolism in rhizosphere bacteria. These findings suggest that intercropping could provide a promising strategy to overcome challenges associated with continuous tobacco cropping by regulating the rhizosphere environment.
| S-EPMC11533348 | biostudies-literature
Project description:Soil microorganisms could affect the quality of tobacco leaves, however, little is known about the association of tobacco chemical components and soil fungal communities. In the present study, the relationship between soil fungi and tobacco quality based on chemical components in Bijie was investigated. The results showed that the total harmony scores (THS) of the analyzed tobacco leaves ranged from 46.55 ± 3.5 to 91.55 ± 2.25. Analyses of chemical components revealed that high contents of nicotine (≥ 1.06%) and sugar (total sugar: ≥ 22.96%, reducing sugar: ≥ 19.62%), as well as low potassium level (≤ 2.68%) were the main factors limiting the quality of flue-cured tobacco leaves. Pearson correlation analysis indicated that soil nitrate, available potassium/phosphorous, and organic matter significantly correlated with tobacco nicotine, potassium, and chloride levels (p < 0.05). Besides, the analysis of alpha- and beta-diversity of soil fungal communities implied that fungal structure rather than the richness affected the chemical quality of tobacco. In detail, the relative abundance of Humicola olivacea species in soils was positively correlated with the THS of tobaccos (r = 0.52, p < 0.05). Moreover, the species including Mortierella alpina, Mortierella hyalina, Tausonia pullulan, and Humicola olivacea were negatively correlated with tobacco sugar (r ≤ - 0.45, p < 0.05) while, Codinaea acaciae and Saitozyma podzolica species were negatively correlated with tobacco nicotine (r ≤ - 0.51, p < 0.05). The present study provides a preliminary basis for utilizing fungal species in soils to improve the chemical quality of tobacco in the studied area.
| S-EPMC8857190 | biostudies-literature
Project description:Nitrate is an important precursor of tobacco-specific nitrosamines (TSNAs) and a remarkable difference in nitrate accumulation between lamina and midrib of flue-cured tobacco has long been observed. However, the physiological and molecular mechanisms underpinning this difference remain poorly understood. In this study, physiological and genetic factors impacting nitrate accumulation were identified in pot experiments using flue-cured tobacco K326 with contrasting nitrate content between lamina and midrib. The results showed that three times higher NO3-N content was observed in midrib than that in the lamina, along with lower pigment, NH4-N content, nitrate reductase activity (NRA), sucrose synthetase activity (SSA), and glutamine synthetase activity (GSA) in midrib. Transcriptome analysis revealed that expression of genes involved in porphyrin and chlorophyll metabolism, carotenoid biosynthesis, photosynthesis-antenna proteins, photosynthesis, carbon fixation in photosynthetic organisms, starch and sucrose metabolism, nitrogen metabolism, and biosynthesis of amino acids were significantly lower in midrib than in lamina. qRT-PCR results showed that the expression level of nitrate transporter genes LOC107782967, LOC107806749, LOC107775674, LOC107829632, LOC107799198, LOC107768465 decreased by 2.74, 1.81, 49.5, 3.5, 2.64 and 2.96-folds while LOC107789301 increased by 8.23-folds in midrib but not in lamina. Reduced chlorophyll content might result in low carbohydrate formation which is the source of energy and carbon skeleton supply, then the low capacity of nitrogen reduction, assimilation and transportation, and the poor ability of nitrate reallocation but the high capacity of accumulation might lead to nitrate accumulation in midrib. The results laid the foundation for reducing nitrate content and TSNA formation in tobacco midribs and their products.
| S-EPMC8861034 | biostudies-literature
Project description:Nitrate accumulation in tobacco (Nicotiana tabacum L.) leaf, particularly in the burley (BU) type, is a reservoir for the generation of nitrosating agents responsible for the formation of tobacco-specific nitrosamines (TSNAs). TSNAs are mainly produced via the nitrosation of alkaloids occurring during the curing of tobacco leaves. Additional formation of TSNAs may also occur during tobacco storage, leaf processing and in some circumstances via pyrosynthesis during combustion. Two TSNA species, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN) are found in the tobacco products and have been documented to be animal carcinogens. A previous study showed that decreasing the accumulation of nitrate in tobacco leaf via the overexpression of a deregulated form of nitrate reductase is efficient to reduce the production of TSNAs. We pursue in finding another molecular genetic target to lower nitrate in BU tobacco. Suppressing expression or knocking-out CLCNt2 has a direct impact on leaf nitrate and TSNA reduction in cured leaves without altering biomass. This study provides now a straight path toward the development of new commercial tobacco varieties with reduced TSNA levels by breeding of variants deficient in active CLCNt2 copies.
| S-EPMC8888935 | biostudies-literature
Project description:Tobacco (Nicotiana tabacum) is a globally cultivated crop, with its quality closely associated with the color and chemical composition of cured tobacco leaves. In this experiment, the effects of spraying exogenous 2, 4-epibrassinolide (EBR) and melatonin (MT) on the development of tobacco leaves at maturity stage and the quality after curing were investigated. Both EBR and MT treatments significantly enhanced the appearance quality of tobacco leaves at the stem-drying stage. Following preharvest applications, the sugar-to-alkali ratio and potassium content increased, while the contents of starch, total alkaloids, and proteins decreased. The levels of conventional chemical components were improved, enhancing the overall coordination of the tobacco. Transcriptome analysis revealed that EBR treatment down-regulated the chlorophyll biosynthetic genes hemA, MgPEC, and ChlD, while up-regulating the chlorophyll degradation genes CHL2, SGR, and PAOs. Similarly, MT treatment down-regulated the chlorophyll biosynthetic genes FC2 and MgPEC and up-regulated the degradation genes CHL2 and SGR, thus promoting chlorophyll degradation. Furthermore, in the downstream carotenoid biosynthetic pathway, both EBR and MT treatments regulated abscisic acid-related genes, with NCEDs being up-regulated and CYP707A1s down-regulated, thereby promoting the leaf ripening. Metabolomics analysis indicated that EBR treatment primarily regulated alkaloids, terpenoids, and flavonoids, while MT treatment mainly affected flavonoids. Both treatments also reduced the accumulation of the harmful substance aristolochic acid B. Comprehensive evaluations of appearance quality, physiological parameters, transcriptome, and metabolomics analyses demonstrated that exogenous spraying of EBR and MT treatments improved the maturity and quality of cured tobacco leaves, with EBR treatment exhibiting a greater effect than MT treatment.
| S-EPMC11644396 | biostudies-literature
Project description:To study the relationship between the diversity of the surface microbial community and tobacco flavor, and to improve tobacco quality using microorganisms. The microbial community composition and diversity of 14 samples of flue-cured tobacco from tobacco-producing areas in Yunnan with varying grades were analyzed by high-throughput sequencing. PICRUSt was used for predicting microbial functions. A strain of Bacillus amyloliquefaciens W6-2 with the ability to degrade pectin was screened from the surface of flued-cured tobacco leaves from Yunnan reroasted tobacco leave. The enzyme preparation was prepared through fermentation and then applied for treating flue-cured tobacco. The improvement effect was evaluated by measuring the content of macromolecule and the changes in volatile components, combined with sensory evaluations. The bacterial communities on the surface of flue-cured tobacco exhibited functional diversity, consisting primarily of Variovorax, Pseudomonas, Sphingomonas, Burkholderia, and Bacillus. These bacterial strains played a role in the aging process of flue-cured tobacco leaves by participating in amino acid metabolism and carbohydrate metabolism. These metabolic activity converted complex macromolecules into smaller molecular compounds, ultimately influence the smoking quality and burning characteristics of flue-cured tobacco. The pectinase preparation produced through fermentation using W6-2 has been found to enhance the aroma and sweetness of flue-cured tobacco, leading to improved aroma, reduced impurities, and enhanced smoothness. Additionally, the levels of pectin, cellulose, and hemicellulose decreased, while the levels of water-soluble sugar and reducing sugar increased, and the contents of esters, ketones, and aldehydes increased, and the contents of benzoic acid decreased. The study revealed the correlation between surface microorganisms and volatile components of Yunnan tobacco leaves, and the enzyme produced by the pectin-degrading bacteria W6-2 effectively improved the quality of flue-cured tobacco.
| S-EPMC10955059 | biostudies-literature