Systemic Resistance In Tobacco Research Articles

6-pentyl-α-pyrone from Trichoderma koningii induces systemic resistance in tobacco against tobacco mosaic virus

This study aimed at evaluating the ability of 6-pentyl-α-pyrone (6PP) isolated from Trichoderma koningii CTX1172 (AUMC 11520), an endophytic fungal strain to induce systemic resistance in tobacco (Nicotiana tabacum cv. White Burley) plant against tobacco mosaic virus (TMV). 6PP exhibited 10–60% symptoms inhibition at low concentrations (10–30 μg mL−1) achieving 100% biocontrol efficacy at high concentrations (40 and 50 μg mL−1), compared with control. Using DAS-ELISA technique for detection of TMV (expressed by decreasing in absorbance value), the TMV detection was significantly reduced in plants treated with 6PP at low concentrations compared with plants inoculated with TMV only and it was almost undetectable in plants treated with high concentrations, as well as healthy control plants. Application of 6PP not only increased the accumulation of proline as a non-enzymatic antioxidant compound, but also increased the activities of pathogenesis-related enzymes (superoxide dismutase, peroxidase and polyphenol oxidase), indicating that 6PP acts as elicitor for induction of resistance in tobacco against TMV. On the molecular level, plants treated with 6PP also showed augmented and rapid expression of defense-related genes including PR-a, PR-b and PR-10. This study was the first to imply the potential of a pyrone compound in biocontrol of plant viral disease.

A genetic tool for production of GFP-expressing Rhodopseudomonas palustris for visualization of bacterial colonization

Development of a genetic tool for visualization of photosynthetic bacteria (PSB) is essential for understanding microbial function during their interaction with plant and microflora. In this study, Rhodopseudomonas palustris GJ-22-gfp harboring the vector pBBR1-pckAPT-gfp was constructed using an electroporation transformation method and was used for dynamic tracing of bacteria in plants. The results showed that strain GJ-22-gfp was stable and did not affect the biocontrol function, and the Confocal Laser Scanning Microscopy (CLSM) results indicated it could successfully colonised on the surface of leaf and root of tobacco and rice. In tobacco leaves, cells formed aggregates on the mesophyll epidermal cells. While in rice, no aggregate was found. Instead, the fluorescent cells colonise the longitudinal intercellular spaces between epidermal cells. In addition, the results of strain GJ-22 on the growth promotion and disease resistance of tobacco and rice indicated that the different colonization patterns might be related to the bacteria could induce systemic resistance in tobacco.

A novel protein elicitor PeFOC1 from Fusarium oxysporum triggers defense response and systemic resistance in tobacco

In recent years, it is a hotspot research field on interaction mechanism between elicitor and plant. In this study, a novel hypersensitive response (HR)-inducing protein elicitor was isolated from the culture filtrate of Fusarium oxysporum f. sp. cubense and named PeFOC1, which consisted of 321 amino acids with a molecular weight of approximately 35 kDa. After the inducible expression in Escherichia coli and purification by ÄKTA explore system, the recombinant PeFOC1 also triggered a typical HR in tobacco. In addition, PeFOC1 induced a cascade of defense response in tobacco including production of hydrogen peroxide, deposition of callose, and accumulation of phenolic compounds. Moreover, PeFOC1 significantly improved systemic resistance of tobacco seedlings to tobacco mosaic virus and Pseudomonas syringae pv. tabaci. Real-time quantitative-PCR analysis indicated that several defense-related genes in tobacco, such as NtPR1a, NtNPR1, NtPAL, NtEDS1, NtPDF, and NtLOX, were all up-regulated by the treatment of PeFOC1. All these results collectively demonstrated that PeFOC1 triggered defense response and systemic acquired resistance (SAR) in tobacco. This research not only provides further research on immune mechanism between plant and elicitor, but also sheds new light on strategy for biocontrol in the future.

Exogenous application of phenylacetic acid promotes root hair growth and induces the systemic resistance of tobacco against bacterial soft-rot pathogen Pectobacterium carotovorum subsp. carotovorum.

Phenylacetic acid (PAA) was evaluated for its capability to promote plant growth and induce systemic resistance in tobacco (Nicotianum tabacum L cv. Xanthi) against the bacterial soft rot pathogen Pectobacterium carotovorum subsp. carotovorum (PCC). Exogenous application of PAA influenced root formation, the activities of defence-related enzymes and the expression of defence and growth-related genes. Increased formation of lateral roots can be observed in tobacco treated with higher PAA concentrations. The highest elicitation of induced systemic resistance (ISR) was found in plants treated with 0.5mM PAA, where the phytotoxic effect was minimal. The activities of the defence enzymes phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphnenoloxidase (PPO) were modulated upon treatment with different PAA concentrations. Reverse transcription-PCR analyses showed that 0.5mM PAA modulated the expression of the growth-related genes NtEXP2 and NtEXP6, and the defence-related genes Coi1, NPR1, PR-1a and PR-1b. These results showed that different concentrations of PAA can elicit different responses and effects on tobacco growth and resistance. This study presents the important role of PAA not only on plant growth but also for plant immunity against phytopathogens.

Bacillus volatiles adversely affect the physiology and ultra-structure of Ralstonia solanacearum and induce systemic resistance in tobacco against bacterial wilt

Volatile organic compounds (VOCs) produced by various bacteria have significant potential to enhance plant growth and to control phytopathogens. Six of the most effective antagonistic Bacillus spp. were used in this study against Ralstonia solanacearum (Rsc) TBBS1, the causal agent of bacterial wilt disease in tobacco. Bacillus amyloliquefaciens FZB42 and Bacillus artrophaeus LSSC22 had the strongest inhibitory effect against Rsc. Thirteen VOCs produced by FZB42 and 10 by LSSC22 were identified using gas chromatography-mass spectrometry analysis. Benzaldehyde, 1,2-benzisothiazol-3(2 H)-one and 1,3-butadiene significantly inhibited the colony size, cell viability, and motility of pathogens and negatively influenced chemotaxis. Transmission and scanning electron microscopy revealed severe morphological and ultra-structural changes in cells of Rsc. Furthermore, VOCs altered the transcriptional expression level of PhcA (a global virulence regulator), type III secretion system (T3SS), type IV secretion system (T4SS), extracellular polysaccharides and chemotaxis-related genes, which are major contributors to pathogenicity, resulting in decreased wilt disease. The VOCs significantly up-regulated the expression of genes related to wilt resistance and pathogen defense. Over-expression of EDS1 and NPR1 suggest the involvement of SA pathway in induction of systemic resistance. Our findings provide new insights regarding the potential of antibacterial VOCs as a biocontrol tool against bacterial wilt diseases.

BDP-30, a systemic resistance inducer from Boerhaavia diffusa L., suppresses TMV infection, and displays homology with ribosome-inactivating proteins.

Root extract of Boerhaavia diffusa L. induced systemic resistance in tobacco against Tobacco mosaic virus. A 30 kDa protein was isolated as the active component, called BDP-30 on the basis of the molecular weight and source plant. BDP-30, a glycoprotein, was found to be temperature and protease resistant. It was basic, possessing a pI greater than 9.0. In-gel proteolytic digestion of BDP-30 generated two peptides that possessed the amino acid sequence KLYDIPPLR and KVTLPYSGNYER by LC/MS/MS. Both peptides shared absolute sequence identity with trichosanthin, a ribosome-inactivating protein from Trichosanthes kirilowii, and a 78 percent and 100 percent homology respectively with an RIP from Bryonia dioica, bryodin. Further, effort was made to look at the fate of TMV in induced resistant Nicotiana tabacum cv. Xanthi, a systemic host of the virus, at specified days after inoculation in control and treated plants. TMV coat protein (CP) was detected by immunoblot 7 days post inoculation up to 21 days in the control set, but not in treated resistant plants. TMV RNA was detected by RT-PCR using TMV-CP specific primers. Resistant tobacco did not show presence of TMV RNA up to 21 days of inoculation. This suggests that BDP-30 may be suppressing TMV replication.

Proteomic Analysis of a Global Regulator GacS Sensor Kinase in the Rhizobacterium, Pseudomonas chlororaphis O6

The GacS/GacA system in the root colonizer Pseudomonas chlororaphis O6 is a key regulator of many traits relevant to the biocontrol function of this bacterium. Proteomic analysis revealed 12 proteins were down-regulated in a gacS mutant of P. chlororaphis O6. These GacS-regulated proteins functioned in combating oxidative stress, cell signaling, biosynthesis of secondary metabolism, and secretion. The extent of regulation was shown by real-time RT-PCR to vary between the genes. Mutants of P. chlororaphis O6 were generated in two GacS-regulated genes, trpE, encoding a protein involved in tryptophan synthesis, and prnA, required for conversion of tryptophan to the antimicrobial compound, pyrrolitrin. Failure of the trpE mutant to induce systemic resistance in tobacco against a foliar pathogen causing soft rot, Pectobacterium carotovorum SCCI, correlated with reduced colonization of root surfaces implying an inadequate supply of tryptophan to support growth. Although colonization was not affected by mutation in the prnA gene, induction of systemic resistance was reduced, suggesting that pyrrolnitrin was an activator of plant resistance as well as an antifungal agent. Study of mutants in the other GacS-regulated proteins will indicate further the features required for biocontrol-activity in this rhizobacterium.

Induction of systemic resistance in tobacco against Tobacco mosaic virus by Bacillus spp.

Bacillus pumilus strain EN16 and Bacillus subtilis strain SW1 were tested for their systemic resistance and protection abilities against tobacco mosaic virus disease under greenhouse conditions. The results showed that strain EN16 and SW1 treatment significantly reduced mosaic symptoms and disease severity, resulting in 52 and 71% protection at 14 days of inoculation, respectively. A decreased amount of virus was detected in EN16- or SW1-treated tobacco plants by ELISA. Moreover, 5- and 7-day intervals between inducer treatment and pathogen inoculations were respectively required for strain EN16 and SW1 to induce optimal resistance. Further analysis on phenylalanine ammonia-lyase, peroxidase, polyphenol oxidase and pathogenesis-related (PR) proteins in tobacco showed that the amounts of defense enzymes and PR proteins significantly increased in Bacillus-treated plants challenged with pathogen when compared to control.

Antimicrobial peptaibols induce defense responses and systemic resistance in tobacco against tobacco mosaic virus

Trichoderma spp. are well-known biocontrol agents because of their antimicrobial activity against bacterial and fungal phytopathogens. However, the biochemical mechanism of their antiviral activity remains largely unknown. In this study, we found that Trichokonins, antimicrobial peptaibols isolated from Trichoderma pseudokoningii SMF2, could induce defense responses and systemic resistance in tobacco (Nicotiana tabacum var. Samsun NN) against tobacco mosaic virus (TMV) infection. Local Trichokonin (100 nM) treatment led to 54% lesion inhibition, 57% reduction in average lesion diameter and 30% reduction in average lesion area in systemic tissue of tobacco compared with control, indicating that Trichokonins induced resistance in tobacco against TMV infection. Trichokonin treatment increased the production of reactive oxygen species and phenolic compounds in tobacco. Additionally, application of Trichokonins significantly increased activities of pathogenesis-related enzymes PAL and POD, and upregulated the expression of several plant defense genes. These results suggested that multiple defense pathways in tobacco were involved in Trichokonin-mediated TMV resistance. We report on the antivirus mechanism of peptaibols, which sheds light on the potential of peptaibols in plant viral disease control.

Mutation in the edd gene encoding the 6-phosphogluconate dehydratase of Pseudomonas chlororaphis O6 impairs root colonization and is correlated with reduced induction of systemic resistance

The primary objective of this study was to determine the role of 6-phosphogluconate dehydratase in root colonization and the induction of systemic resistance by the rhizobacterium, Pseudomonas chlororaphis O6. The edd gene encoding for 6-phosphogluconate dehydratase, which is one of the key enzymes in glucose utilization, was cloned. Transcription of the gene was higher in medium containing sugars than with organic acids. An edd mutant failed to grow on glucose but grew on organic acids. The edd mutant colonized tobacco roots at wild-type levels early after inoculation, but levels were lower by 12 days. The edd mutant failed to induce the systemic resistance in tobacco to a soft-rot pathogen at wild-type level. 6-Phosphogluconate dehydratase in P. chlororaphis O6 contributes to root colonization and induction of systemic resistance presumably as the consequence of its essential role in the Entner-Doudoroff (ED) pathway. Metabolism of sugars through the ED pathway in P. chlororaphis O6 may be important because it facilitates the production of inducers of systemic resistance including butanediol.

GacS-Dependent Production of 2R, 3R-Butanediol by Pseudomonas chlororaphis O6 Is a Major Determinant for Eliciting Systemic Resistance Against Erwinia carotovora but not Against Pseudomonas syringae pv. tabaci in Tobacco

Root colonization by a plant-beneficial rhizobacterium, Pseudomonas chlororaphis O6, induces disease resistance in tobacco against leaf pathogens Erwinia carotovora subsp. carotovora SCC1, causing soft-rot, and Pseudomonas syringae pv. tabaci, causing wildfire. In order to identify the bacterial determinants involved in induced systemic resistance against plant diseases, extracellular components produced by the bacterium were fractionated and purified. Factors in the culture filtrate inducing systemic resistance were retained in the aqueous fraction rather than being partitioned into ethyl acetate. Fractionation on high-performance liquid chromatography followed by nuclear magnetic resonance mass spectrometry analysis identified the active compound as 2R, 3R-butanediol. 2R, 3R butanediol induced systemic resistance in tobacco to E. carotovora subsp. carotovora SCC1, but not to P. syringae pv. tabaci. Treatment of tobacco with the volatile 2R, 3R-butanediol enhanced aerial growth, a phenomenon also seen in plants colonized by P. chlororaphis O6. The isomeric form of the butanediol was important because 2S, 3S-butandiol did not affect the plant. The global sensor kinase, GacS, of P. chlororaphis O6 was a key regulator for induced systemic resistance against E. carotovora through regulation of 2R, 3R-butanediol production. This is the first report of the production of these assumed fermentation products by a pseudomonad and the role of the sensor kinase GacS in production of 2R, 3R-butanediol.

Induced defence in tobacco by Pseudomonas chlororaphis strain O6 involves at least the ethylene pathway

The antifungal phenazines produced by certain root colonizing pseudomonads are credited with contributing to the biocontrol activity of these isolates. However, the phenazine producer Pseudomonas chlororaphis O6 also induces systemic resistance in tobacco. Protection against two foliar bacterial pathogens, the wild fire pathogen, Pseudomonas syringae pv. tabaci, and Erwinia carotovora subsp. carotovora that causes a soft rot, was observed. A mutation in the bacterial global regulator gacS gene eliminated certain secondary traits, including phenazine production, but did not prevent induction of resistance in tobacco to P. syringae pv. tabaci. However, induction of resistance to E. carotovora subsp. carotovora was impaired in plants colonized by the GacS mutant compared to the level of protection in plants colonized by wild-type P. chlororaphis O6. Colonization by both the wild-type and the GacS mutant caused increased accumulation for transcripts of plant defense genes regulated by ethylene. Tobacco transformed with a mutant etr1 gene to reduce ethylene sensitivity did not display induced resistance to E. carotovora when colonized by P. chlororaphis O6. We conclude that inducers other than phenazines appear to initiate the pathways for systemic resistance induced by P. chlororaphis O6.

Activation of PR-1a Promoter by Rhizobacteria That Induce Systemic Resistance in Tobacco against Pseudomonas syringae pv. tabaci

Investigations were conducted to determine whether induction of PR-1a gene promoter was correlated with systemic resistance, induced by rhizobacteria, against wildfire disease of tobacco. Ten different strains of plant growth-promoting rhizobacteria (PGPR), including the species Bacillus pumilus, Serratia marcescens, Pseudomonas fluorescens, P. putida, Curtobacterium flaccumfaciens, and Bukholderia gladioli, were tested. Induction of PR-1a gene activity was assessed using transgenic tobacco plants expressing the β-glucuronidase (GUS) gene fused to the PR-1a gene promoter. In a microtiter plate assay, GUS activity was significantly enhanced, compared to that of water-treated controls by salicylic acid (SA), four PGPR strains with known induced systemic resistance activity, and one endophytic bacterium previously shown to lack induced systemic resistance activity in cucumber. No enhanced GUS activity was noted with three control bacteria (two plant-associated strains and Escherichia coli strain HB-101). In a separate assay, infiltration of greenhouse-grown tobacco leaves with these same bacteria resulted in significant increases in GUS activity compared to that of the water-treated control, for all strains which induced GUS activity in the microtiter plate assay. The two plant-associated bacterial controls did not affect GUS activity. Treatment of tobacco with SA and all bacterial strains which enhanced GUS activity in the microtiter and leaf assays led to reduced symptoms of wildfire disease caused by Pseudomonas syringae pv. tabaci in the greenhouse, whereas none of the three control bacterial strains significantly affected disease. These results support the conclusion that induction of PR-1a promoter activity and PGPR-mediated induced systemic disease resistance are linked events for the PGPR strains studied.

Pseudomonas aeruginosa 7NSK2-induced systemic resistance in tobacco depends on in planta salicylic acid accumulation but is not associated with PR1a expression

Root colonization by rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to systemic acquired resistance induced by a localized pathogen infection. We used the tobacco–tobacco mosaic virus model to investigate whether the systemic resistance induced by the rhizobacterium Pseudomonas aeruginosa 7NSK2 is mediated by the systemic acquired resistance signal transduction pathway. Experiments with nahG-transformed tobacco revealed that Pseudomonas aeruginosa 7NSK2-induced resistance depended on in planta salicylic acid accumulation for its expression but not for its induction and is, in this respect, similar to systemic acquired resistance. However, Pseudomonas aeruginosa 7NSK2-induced resistance was, unlike systemic acquired resistance, not associated with PR1a expression at the time of challenge with tobacco mosaic virus. This suggests that Pseudomonas aeruginosa 7NSK2 treatment would only potentiate defense gene expression in systemic tissue, which would also explain why its level of resistance is lower than in case of systemic acquired resistance. Because we demonstrated that induced resistance by Pseudomonas aeruginosa 7NSK2 exclusively depends on the production of salicylic acid by this strain our conclusions might also account for other salicylic acid-producing and resistance-inducing rhizobacteria.

Salicylic Acid Biosynthetic Genes Expressed in Pseudomonas fluorescens Strain P3 Improve the Induction of Systemic Resistance in Tobacco Against Tobacco Necrosis Virus

ABSTRACT Application of salicylic acid induces systemic acquired resistance in tobacco. pchA and pchB, which encode for the biosynthesis of salicylic acid in Pseudomonas aeruginosa, were cloned into two expression vectors, and these constructs were introduced into two root-colonizing strains of P. fluorescens. Introduction of pchBA into strain P3, which does not produce salicylic acid, rendered this strain capable of salicylic acid production in vitro and significantly improved its ability to induce systemic resistance in tobacco against tobacco necrosis virus. Strain CHA0 is a well-described biocontrol agent that naturally produces salicylic acid under conditions of iron limitation. Introduction of pchBA into CHA0 increased the production of salicylic acid in vitro and in the rhizosphere of tobacco, but did not improve the ability of CHA0 to induce systemic resistance in tobacco. In addition, these genes did not improve significantly the capacity of strains P3 and CHA0 to suppress black root rot of tobacco in a gnotobiotic system.

Induction of Systemic Resistance in Tobacco Against Metalaxyl-Tolerant Strains ofPeronospora tabacinaand the Natural Occurrence of the Phenomenon in Mexico

Field experiments were conducted in San Andres Tuxtla, Veracruz, Mexico, during 1986 and 1989 to test the effectiveness of induced systemic resistance (immunization) against metalaxyl-tolerant strains of Peronospora tabacina, causal agent of tobacco blue mold. Plants of Nicotiana tabacum cultivar Jaltepec were stem-injected with sporangiospores of metalaxyl-tolerant strains of P. tabacina. Half of the plants were treated with metalaxyl (...)

Induction by 2-chloroethylphosphonic acid of viral-like lesions, associated proteins, and systemic resistance in tobacco

Pricking Samsum NN tobacco leaves with needles moistened with the ethylene-releasing compound 2-chloroethylphosphonic acid (ethephon) gave rise to necrotic spots resembling virus-induced local lesions. Treatment with ethephon resulted in changes in protein constitution and peroxidase isoenzyme patterns qualitatively and quantitatively similar to those induced by tobacco mosaic virus (TMV). Moreover, a systemic resistance was induced comparable to the result of virus infection. Abundant local ethylene synthesis during TMV infection thus seems to be a causative factor in redirecting plant metabolism during the hypersensitive reaction.