Expression Of Pathogenesis-related Protein Genes Research Articles

Penicillium simplicissimum and Trichoderma asperellum counteract the challenge of Puccinia striiformis f. sp. tritici in wheat plants

BackgroundYellow (stripe) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an economic disease of wheat. Growth-promoting fungi (GPF) such as Trichoderma asperellum and Penicillium simplicissimum have been investigated for their potential to control yellow rust and their involvement in gene expression of four PR proteins for all-stage resistance.ResultsWheat plants (cv. Sids-12) treated individually with each of the biocontrol agents, P. simplicissimum and T. asperellum, at 24 and 48 hpi showed a resistance response (infection type = 2) to yellow rust, compared to the non-treated plants, which showed highly susceptible response (infection type = 9). Both biocontrol agents induced resistance against yellow rust on wheat plants, exhibiting a moderate resistance (10 MR) and reduced the colony size of Pst (0.6 mm2). Moreover, P. simplicissimum and T. asperellum increased (P ≤ 0.05) the grain yields of wheat plants infected with Pst. Scanning electron microscope (SEM) of yellow rust infected wheat leaves treated with P. simplicissimum and T. asperellum at 24 and 48 hpi showed hyperparasitism on Pst urediniospores and inhibition of the spore germination. Expressions of pathogenesis-related (PR) protein genes, PR1, PR2, PR3 and PR4 were higher in wheat plants treated with both biocontrol agents than the non-treated checks.ConclusionP. simplicissimum and T. asperellum exhibited biocontrol potential against yellow rust disease caused by P. striiformis f. sp. tritici (Pst) on wheat plants. It was found that wheat defence mechanism against Pst was activated by a high expression of PR protein genes induced by both biocontrol agents.

Global analysis of lysine 2-hydroxyisobutyrylation during Fusarium graminearum infection in maize.

Proteins post-translational modification (PTMs) is necessary in the whole life process of organisms. Among them, lysine 2-hydroxyisobutyrylation (Khib) plays an important role in protein synthesis, transcriptional regulation, and cell metabolism. Khib is a newly identified PTM in several plant species. However, the function of Khib in maize was unclear. In this study, western blotting results showed that Khib modification level increased significantly after Fusarium graminearum infection, and 2,066 Khib modified sites on 728 proteins were identified in maize, among which 24 Khib sites occurred on core histones. Subcellular localization results showed that these Khib modified proteins were localized in cytoplasm, chloroplast, and nucleus. Then, comparative proteomic analysis of the defense response to F. graminearum infection showed that Khib modification participated in plant resistance to pathogen infection by regulating glycolysis, TCA cycle, protein synthesis, peroxisome, and secondary metabolic processes, such as benzoxazinoid biosynthesis, phenylpropanoid biosynthesis, jasmonic acid synthesis, and tyrosine and tryptophan biosynthesis. In addition, we also demonstrated that lysine 2-hydroxyisobutyrylation sites on histones were involved in the gene expression of pathogenesis-related proteins. Our results provide a new perspective for the study of plant disease resistance, and had directive significance of maize disease resistance for molecular breeding.

Efficiency of plant growth regulators as inducers for improve systemic acquired resistance against stripe rust disease caused by Puccinia striiformis f. sp. tritici in wheat through up-regulation of PR-1 and PR-4 genes expression

Systemic acquired resistance (SAR) induced by five different phytohormones (plant growth regulators); salicylic acid (SA), abscisic acid (ABA), indole 3-butyric acid (IBA), indoleacetic acid (IAA) and naphthaleneacetic acid (NAA) was investigated against Puccinia striiformis f. sp. tritici (pst) in the Egyptian susceptible wheat genotype Sids-12. Seedlings were sprayed with three different concentrations of each phytohormones and inoculated by uredospore of pst then evaluated against the germination. Results indicated that, all the five chemical inducers were able to inhibit spore germination and showed highly significant differences among treatments, while, ABA and NAA recorded the lowest germination and the highest inhibition percentages at the low concentration (50 μg/ml). Also, all treatments reduced infection type values and numbers of pustules/leaf compared with control (untreated treatment). ABA treatment at concentration of 50 μg/ml was capable to induce complete protection for the susceptible wheat cultivar, Sids-12 by significant reduction of infection type (0) compared with control. On the other side, relative gene expression of two pathogenesis-related (PR) protein genes; the antifungal protein (PR-1) and the endochitinase (PR-4) were evaluated for the treated seedlings in all treatments at three different time points comparing with untreated plants and the resistant wheat genotype Misr-3. Results showed up-regulation of gene expressions in all treatments for the two tested genes at the three time points (1, 2 and 7 days after inoculation) comparing with control and most of treatments comparing with the resistant genotype Misr-3. This over expression of PR protein genes might be definitive in activation of the host defense mechanism against Pst and playing the important role of resistance induced by chemical inducers as phytohormones in wheat. Also, it was found that ABA treatment was more efficient in inducing the resistance to wheat stripe rust disease than other chemical inducers. The obtained results indicated that phytohormones as inducers can be used to management stripe rust disease in wheat.

Trichoderma asperelloides PSU-P1 Induced Expression of Pathogenesis-Related Protein Genes against Gummy Stem Blight of Muskmelon (Cucumis melo) in Field Evaluation

Gummy stem blight caused by Stagonosporopsis cucurbitacearum is the most destructive disease of muskmelon cultivation. This study aimed to induce disease resistance against gummy stem blight in muskmelon by Trichoderma asperelloides PSU-P1. This study was arranged into two crops. Spore suspension at a concentration of 1 × 106 spores/mL of T. asperelloides PSU-P1 was applied to muskmelon to investigate gene expression. The expression of PR genes including chitinase (chi) and β-1,3-glucanase (glu) were determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR), and enzyme activity was assayed by the DNS method. The effects of T. asperelloides PSU-P1 on growth, yield, and postharvest quality of muskmelon fruit were measured. A spore suspension at a concentration of 1 × 106 spore/mL of T. asperelloides PSU-P1 and S. cucurbitacearum was applied to muskmelons to determine the reduction in disease severity. The results showed that the expression of chi and glu genes in T. asperelloides PSU-P1-treated muskmelon plants was 7–10-fold higher than that of the control. The enzyme activities of chitinase and β-1,3-glucanase were 0.15–0.284 and 0.343–0.681 U/mL, respectively, which were higher than those of the control (pathogen alone). Scanning electron microscopy revealed crude metabolites extracted from T. asperelloides PSU-P1-treated muskmelon plants caused wilting and lysis of S. cucurbitacearum hyphae, confirming the activity of cell-wall-degrading enzymes (CWDEs). Application of T. asperelloides PSU-P1 increased fruit weight and fruit width; sweetness and fruit texture were not significantly different among treated muskmelons. Application of T. asperelloides PSU-P1 reduced the disease severity scale of gummy stem blight to 1.10 in both crops, which was significantly lower than that of the control (2.90 and 3.40, respectively). These results revealed that application of T. asperelloides PSU-P1 reduced disease severity against gummy stem blight by overexpressed PR genes and elevated enzyme activity in muskmelon plants.

Oligosaccharins as Elicitors of Defense Responses in Wheat.

Wheat is a highly relevant crop worldwide, and like other massive crops, it is susceptible to foliar diseases, which can cause devastating losses. The current strategies to counteract wheat diseases include global monitoring of pathogens, developing resistant genetic varieties, and agrochemical applications upon diseases’ appearance. However, the suitability of these strategies is far from permanent, so other alternatives based on the stimulation of the plants’ systemic responses are being explored. Plants’ defense mechanisms can be elicited in response to the perception of molecules mimicking the signals triggered upon the attack of phytopathogens, such as the release of plant and fungal cell wall-derived oligomers, including pectin and chitin derivatives, respectively. Among the most studied cell wall-derived bioelicitors, oligogalacturonides and oligochitosans have received considerable attention in recent years due to their ability to trigger defense responses and enhance the synthesis of antipathogenic compounds in plants. Particularly, in wheat, the application of bioelicitors induces lignification and accumulation of polyphenolic compounds and increases the gene expression of pathogenesis-related proteins, which together reduce the severity of fungal infections. Therefore, exploring the use of cell wall-derived elicitors, known as oligosaccharins, stands as an attractive option for the management of crop diseases by improving plant readiness for responding promptly to potential infections. This review explores the potential of plant- and fungal-derived oligosaccharins as a practical means to be implemented in wheat crops.

Control of stripe rust of wheat using indigenous endophytic bacteria at seedling and adult plant stage

Stripe rust (caused by Puccinia striiformis tritici) is one of the most devastating diseases of wheat. The most effective ways to control stripe rust are the use of resistant cultivars and the timely use of an appropriate dose of fungicide. However, the changing nature of rust pathogen outwits the use of resistant cultivars, and the use of a fungicide is associated with environmental problems. To control the disease without sacrificing the environment, we screened 16 endophytic bacteria, which were isolated from stripe rust-resistant wheat cultivars in our previous study, for their biocontrol potential. A total of 5 bacterial strains Serratia marcescens 3A, Bacillus megaterium 6A, Paneibacillus xylanexedens 7A, Bacillus subtilis 11A, and Staphyloccus agentis 15A showed significant inhibition of Puccinia striiformis f. sp. tritici (Pst) urediniospores germination. Two formulations i.e., fermented liquid with bacterial cell (FLBC) and fermented liquid without bacterial cells (FL) of each bacterial strain, were evaluated against the urediniospores germination. Formulations of five selected endophytic bacteria strains significantly inhibited the uredinioospores germination in the lab experiments. It was further confirmed on seedlings of Pakistani susceptible wheat cultivar Inqilab-91 in the greenhouse, as well as in semi-field conditions. FLBC and FL formulations applied 24 h before Pst inoculation (hbi) displayed a protective mode. The efficacy of FLBC was between 34.45 and 87.77%, while the efficacy of FL was between 39.27 and 85.16% when applied 24 hbi. The inoculated wheat cultivar Inqilab-91 was also tested under semi-field conditions during the 2017–2018 cropping season at the adult plant stage. The strains Bacillus megaterium 6A and Paneibacillus xylanexedens 7A alone significantly reduced the disease severity of stripe rust with the efficacy of 65.16% and 61.11% for the FLBC in protective effect, while 46.07% and 44.47% in curative effect, respectively. Inoculated seedlings of Inqilab-91 showed higher activities of antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL). The treated seedlings also showed higher expressions of pathogenesis-related (PR) protein genes, antifungal protein (PR-1), β-1,3-endoglucanases (PR-2), endochitinases (PR-4), peroxidase (PR-9), and ribonuclease-like proteins (PR-10). These results indicated that endophytic bacteria have the biocontrol potential, which can be used to manage stripe rust disease. High production antioxidant enzymes, as well as high expression of PR protein genes, might be crucial in triggering the host defense mechanism against Pst.

Mycorrhiza-induced plant defence responses in trifoliate orange infected by Phytophthora parasitica

Arbuscular mycorrhizal fungi (AMF) reduce disease incidence of host plants through the competition of carbon sources and direct inhibition of pathogens, as well as through induction of biochemical and molecular responses. However, it is not known whether AMF enhance the resistance to Phytophthora parasitica-induced root rot in citrus and what the underlying mechanisms are. This study was carried out to analyze roles of Funneliformis mosseae (a mycorrhizal fungus) in plant defence responses of Poncirus trifoliata infected by P. parasitica. A week after the pathogen infection, mycorrhizal seedlings possessed higher expression of root mitogen-activated protein kinase 3 (PtMAPK3) regardless of P. parasitica infection. F. mosseae induced higher root salicylic acid (SA) concentrations, accompanied with up-regulation of SA synthesis genes (PtPAL1 and PtEPS1), regardless of being infected with P. parasitica or not. Jasmonic acid (JA) synthesis genes were down-regulated by mycorrhization in the absence of P. parasitica and up-regulated (except for PtAOC) by mycorrhization under P. parasitica infection. Moreover, F. mosseae stimulated higher expression of pathogenesis-related protein gene 1 (PtPR1), PtPR4, and PtPR5, especially under P. parasitica infection. F. mosseae inoculation increased levels of root lignin, calmodulin, and total soluble phenol and activities of root chitinase, phenylalanine ammonialyase, and β-1,3-glucanase, and decreased concentrations of root nitric oxide with or without P. parasitica infection. These results implied that F. mosseae elicited MAPKs cascades as well as SA- and calmodulin-mediated signal pathways to activate disease-defence genes, proteins, and compounds to early-warn P. parasitica infection for enhancing tolerance of root rot in trifoliate orange.

Variation in several pathogenesis - Related (PR) protein genes in wheat (Triticum aestivum) involved in defense against Puccinia striiformis f. sp. tritici

Proteins participate in defense mechanisms after a pathogen attacks a host. Pathogenesis-related (PR) proteins in wheat plants play the important role of defense against Puccinia striiformis f. sp. Tritici. This study uses various analytic methods to describe the expression of five (PR) protein genes (PR1, PR2, PR4, PR9 and PR10) and genetic polymorphism among sixteen wheat genotypes to understand the mechanisms underlying of PR genes in Egyptian wheat compared with the Yr genotype. The PR protein genes were semi-quantitatively and quantitatively assessed in four selected wheat genotypes; two resistant (Misr-3 and Yr-29) and two susceptible (Sids-12 and Avocet-S). Reverse transcriptase PCR analysis results indicated that all PR protein genes exhibited different expression levels among the four studied genotypes and overexpression at the resistant genotypes in the different time points of Pst inoculation. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the expression of PR protein genes was elevated in adult plant resistant (APR) genotypes. Plant stage in combination with the infection process by stripe rust provided even greater upregulation in the expression of PR genes and enhanced induction of defense enzyme activities in the same sample at different time points for various wheat genotypes.

MiR159 Represses a Constitutive Pathogen Defense Response in Tobacco.

MicroR159 (miR159) regulation of GAMYB expression is highly conserved in terrestrial plants; however, its functional role remains poorly understood. In Arabidopsis (Arabidopsis thaliana), although GAMYB-like genes are constitutively transcribed during vegetative growth, their effects are suppressed by strong and constitutive silencing by miR159. GAMYB expression occurs only if miR159 function is inhibited, which results in detrimental pleiotropic defects, questioning the purpose of the miR159-GAMYB pathway. Here, miR159 function was inhibited in tobacco (Nicotiana tabacum) and rice (Oryza sativa) using miRNA MIM159 technology. Similar to observations in Arabidopsis, inhibition of miR159 in tobacco and rice resulted in pleiotropic defects including stunted growth, implying functional conservation of the miR159-GAMYB pathway among angiosperms. In MIM159 tobacco, transcriptome profiling revealed that genes associated with defense and programmed cell death were strongly activated, including a suite of 22 PATHOGENESIS-RELATED PROTEIN (PR) genes that were 100- to 1,000-fold upregulated. Constitutive expression of a miR159-resistant GAMYB transgene in tobacco resulted in phenotypes similar to that of MIM159 tobacco and activated PR gene expression, verifying the dependence of the above-mentioned changes on GAMYB expression. Consistent with the broad defense response, MIM159 tobacco appeared immune to Phytophthora infection. These findings suggest that the tobacco miR159-GAMYB pathway functions in the biotic defense response, which becomes activated upon miR159 inhibition. However, PR gene expression was not upregulated in Arabidopsis or rice when miR159 was inhibited, suggesting that miR159-GAMYB pathway functional differences exist between species, or factors in addition to miR159 inhibition are required in Arabidopsis and rice to activate this broad defense response.

Activity in the Arbuscular Mycorrhizal Hyphosphere Warning Neighbouring Plants.

Pathogen infections of the phyllosphere have been investigated in detail, however, the changes induced by these infections on the arbuscular mycorrhizal hyphosphere, and the consequent signalling to the neighbouring plants have been scarcely investigated. Here, our objectives were to document that B.fabae infection of connected Vicia faba plants resulted in changes in the metabolism and microbial community of the hyphosphere, confirming the induction of plant defence in connected plants through gene-expression evaluations. Infected plants were challenged with B. fabae for 72 h. Changes in gene-expression of pathogenesis-related proteins 1,2, and 5 (PR1, PR2, PR5) of both infected- and non-infected plants were analysed, to confirm signalling through the hyphosphere. The primary metabolic profiles and changes in the level of microbiota in the hyphosphere were assessed. Changes in expression of PR1, PR2, and PR5 genes occurred in the neighbouring plants 24 hours after infection. Mannitol levels decreased in presence of AMF. A decrease in the level of actinobacteria in the hyphosphere of infected plants was detected. We conclude that B.fabae infection induced a signalling event through the AM hyphosphere, confirmed by changes in defence gene-expression in non-infected neighbouring plants, influenced primary metabolic activity of-, and affected the microbial composition within-, the AM hyphosphere.

Overexpression of SSBXoc, a Single-Stranded DNA-Binding Protein From Xanthomonas oryzae pv. oryzicola, Enhances Plant Growth and Disease and Salt Stress Tolerance in Transgenic Nicotiana benthamiana.

We previously reported that SSBXoc, a highly conserved single-stranded DNA-binding protein from Xanthomonas spp., was secreted through the type III secretion system (T3SS) and functioned as a harpin-like protein to elicit the hypersensitive response (HR) in the non-host plant, tobacco. In this study, we cloned SsbXoc gene from X. oryzae pv. oryzicola (Xoc), the causal agent of bacterial leaf streak in rice, and transferred it into Nicotiana benthamiana via Agrobacterium-mediated transformation. The expression of SsbXoc in transgenic N. benthamiana enhanced growth of both seedling and adult plants. When inoculated with the harpin Hpa1 or the pathogen Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), the accumulation of reactive oxygen species (ROS) was increased more in SsbXoc transgenic lines than that in wild-type (WT) plants. The expression of pathogenesis-related protein genes (PR1a and SGT1), HR marker genes (HIN1 and HSR203J) and the mitogen-activated protein kinase pathway gene, MPK3, was significantly higher in transgenic lines than in WT after inoculation with Pst DC3000. In addition, SsbXoc transgenic lines showed the enhanced resistance to the pathogenic bacteria P. s. tabaci and the improved tolerance to salt stress, accompanied by the elevated transcription levels of the defense- and stress-related genes. Taken together, these results indicate that overexpression of the SsbXoc gene in N. benthamiana significantly enhanced plant growth and increased tolerance to disease and salt stress via modulating the expression of the related genes, thus providing an alternative approach for development of plants with improved tolerance against biotic and abiotic stresses.

Expression analysis of defense related genes in wheat and maize against Bipolaris sorokiniana

Wheat (Triticum aestivum L.) and maize (Zea mays L.) are important cereal crops grown worldwide. In Pakistan, various varieties of wheat and maize are grown and a number of biotic and abiotic factors influence its production. These are mainly used as a food source and raw material for animal feed. Bipolaris sorokiniana is a hemibiotrophic phytopathogenic fungus that affects various grass species and causes number of diseases on small grains. An investigation was undertaken to evaluate the comparative expression of pathogenesis-related protein genes in wheat and maize under B. sorokiniana stress. After stress, these crops showed disease resistance by improving biochemical parameters like proline, protein, sugar and chlorophyll content. Morpho-physiological parameters including shoot length, root length, relative water content and fresh as well as dry weight were affected by fungal stress. Expression analysis of PR-proteins in stressed plants of wheat confirmed their role in plant defence. PR-1, Thaumatin-like protein (TLP), and β 1,3 glucanase were highly expressed under stress in wheat variety (RWP13), it suggests the role of these genes in the prescribed variety. These genes did not show their expression in susceptible wheat variety (SWG13). Zm PR-5 and Zm 1,3 β-glucanase were highly expressed in maize variety (RMN27) after stress which suggests their role in defence mechanism of this variety. While on the other hand, no significant expression of these genes was observed in susceptible maize variety (SMIG). In future, these genes can be over-expressed in transgenic plants to make them resistant against a number of biotic and abiotic factors.

Biological control of gray mold and growth promotion of tomato using Bacillus spp. isolated from soil

Bacillus strains SG08-09 and SG09-12 were isolated from soil samples collected in garlic fields and screened against Botrytis cinerea, which causes gray mold disease, through dual culture and seedling assays. The effectiveness of these strains as biocontrol agents and their abilities to promote tomato plant growth were evaluated both in the laboratory and under greenhouse conditions. These strains demonstrated many characteristics that are beneficial for plants, such as production of ammonia, indole-3-acetic acid, and siderophores; cellulase and protease activity; and phosphate solubilization. In the greenhouse, both strains controlled B. cinerea and promoted growth of tomato seedlings, as measured by growth increases of 10–42 % for roots and shoots. SG08-09 and SG09-12 reduced disease severity by 67 % and 66 %, respectively, relative to an untreated control. Moreover, SG08-09 induced expression of pathogenesis-related protein genes in tomato, including PR2a and Chi3, in the absence of B. cinerea. Thus, we concluded that both Bacillus strains are useful as potential biocontrol agents in tomato, due to their effects on plant growth and antifungal activities.

Functional characterization of a new pathogen induced xylanase inhibitor (RIXI) from rice

Rice xylanase inhibitor RIXI is a XIP-type inhibitor that belongs to the glycoside hydrolase family 18 (GH18), which includes plant class III chitinases (EC 3.2.1.14) known as PR-8 proteins. The aim of this study was to elucidate whether RIXI had any effect on rice endoxylanase and its role(s) in plant defence. RIXI encoding sequence was cloned from rice (Oryza sativa cv. Nipponbare), and was expressed in Escherichia coli. The activity of recombinant RIXI was investigated – among the tested xylanases, the GH11 xylanase from Aspergillus niger was the most inhibited, while rice endogenous xylanase OSX was least inhibited. Semi-quantitative real-time polymerase chain reaction (PCR) and quantitative real-time PCR showed that the xylanase inhibitor gene RIXI was up-regulated in rice seedlings infected by Magnaporthe grisea. The increased RIXI expression was also accompanied by significantly elevated expression of pathogenesis-related protein gene (PR-1) and class III chitinase gene (Cht-3). This suggested that RIXI might be involved in environmental responses such as defense against phytopathogens.

Cross-Kingdom Effects of Plant-Plant Signaling via Volatile Organic Compounds Emitted by Tomato (Solanum lycopersicum) Plants Infested by the Greenhouse Whitefly (Trialeurodes vaporariorum)

Volatile organic compounds (VOCs) emitted from plants in response to insect infestation can function as signals for the attraction of predatory/parasitic insects and/or repulsion of herbivores. VOCs also may play a role in intra- and inter-plant communication. In this work, the kinetics and composition of VOC emissions produced by tomato (Solanum lycopersicum) plants infested with the greenhouse whitefly Trialeurodes vaporariorum was determined within a 14 days period. The VOC emission profiles varied concomitantly with the duration of whitefly infestation. A total of 36 different VOCs were detected during the experiment, 26 of which could be identified: 23 terpenoids, plus decanal, decane, and methyl salicylate (MeSA). Many VOCs were emitted exclusively by infested plants, including MeSA and 10 terpenoids. In general, individual VOC emissions increased as the infestation progressed, particularly at 7 days post-infestation (dpi). Additional tunnel experiments showed that a 3 days exposure to VOC emissions from whitefly-infested plants significantly reduced infection by a biotrophic bacterial pathogen. Infection of VOC-exposed plants induced the expression of a likely tomato homolog of a methyl salicylate esterase gene, which preceded the expression of pathogenesis-related protein genes. This expression pattern correlated with reduced susceptibility in VOC-exposed plants. The observed cross-kingdom effect of plant-plant signaling via VOCs probably represents a generalized defensive response that contributes to increased plant fitness, considering that resistance responses to whiteflies and biotrophic bacterial pathogens in tomato share many common elements.

Glutathione signaling acts through NPR1-dependent SA-mediated pathway to mitigate biotic stress

Glutathione (GSH) has widely been known to be a multifunctional molecule especially as an antioxidant uptill now, but has found a new role in plant defense signaling. Research from the past three decades indicate that GSH is a player in pathogen defense in plants, but the mechanism underlying this has not been elucidated fully. We have recently shown that GSH acts as a signaling molecule and mitigates biotic stress through non-expressor of PR genes 1 (NPR1)-dependent salicylic acid (SA)-mediated pathway. Transgenic tobacco with enhanced level of GSH (NtGB lines) was found to synthesize more SA, was capable of enhanced expression of genes belonging to NPR1-dependent SA-mediated pathway, were resistant to Pseudomonas syringae, the biotrophic pathogen and many SA-related proteins were upregulated. These results gathered experimental evidence on the mechanism through which GSH combats biotic stress. In continuation with our previous investigation we show here that the expression of glutathione S-transferase (GST), the NPR1-independent SA-mediated gene was unchanged in transgenic tobacco with enhanced level of GSH as compared to wild-type plants. Additionally, the transgenic plants were barely resistant to Botrytis cinerea, the necrotrophic pathogen. SA-treatment led to enhanced level of expression of pathogenesis-related protein gene (PR1) and PR4 as against short-chain dehydrogenase/reductase family protein (SDRLP) and allene oxide synthase (AOS). These data provided significant insight into the involvement of GSH in NPR1-dependent SA-mediated pathway in mitigating biotic stress.

Dry mycelium of Penicillium chrysogenum induces expression of pathogenesis-related protein genes and resistance against wilt diseases in Bt transgenic cotton

Dry mycelium (DM) of Penicillium chrysogenum (PEN), a waste product of the pharmaceutical industry, is used as an organic fertilizer for agricultural production. Our previous studies have indicated that DM of PEN is effective in controlling a number of soil born fungal diseases, but the mode of action is unclear. In the present study, DM of PEN was extracted with water and applied to the roots of the Bt (Bacillus thuringiensis) transgenic cotton (Gossypium hirsutum) cultivar SCRC 21. The efficacy in controlling Fusarium oxysporum f.sp vasinfectum (Fov) and Verticillium dahliae Kleb (Vd), as well as the accumulation of pathogenesis-related (PR) protein transcripts in the plants were examined. The results showed that soil drench with PEN provided significant protection against Fov and Vd. The controlling efficacy of PEN was dose-dependent, and the highest efficacy was obtained with 5–7% PEN. Soil drench with 5% induced the accumulation of six PR protein transcripts, PR-1a, PR-1b, PR-2, PR-3, A-C and B-C in cotyledons of cotton seedlings, suggesting that these PR proteins may be involved in induced resistance against wilt diseases in cotton by PEN. It seems that DM of PEN represents a new agent capable of inducing both resistance and the accumulation of PR protein transcripts.

Phytochromes are possibly involved in regulating expression of pathogenesis-related protein genes in rice

Phytochromes are possibly involved in regulating expression of pathogenesis-related protein genes in rice

Induced expression of pathogenesis-related protein genes in soybean by wounding and the Phytophthora sojae cell wall glucan elicitor

The effects of the glucan elicitor (WGE) from the cell wall of Phytophthora sojae on the transcriptional upregulation of genes representing five families of pathogenesis-related (PR) proteins have been investigated in soybean under wound and minimal-wound conditions. Although each has its own expression pattern, these PR protein genes can be broadly categorized into two groups. Induced expression of genes for PR-1a and PR-10 is predominantly limited to cells proximal to the point of treatment, while that of genes for the elicitor-releasing endo-glucanase (GLU, a PR-2), a WIN-like protein (WIN, a PR-4) and a Kunitz trypsin inhibitor (KTI, a PR-6) is seen in proximal, near-proximal and distal cells. GLU is the only family that shows weak though detectable constitutive (basal) gene expression. Wounding induces only barely detectable to weak expression of genes for PR-1a and KTI and somewhat stronger expression of those for GLU, WIN and PR-10. PR-1a gene expression is essentially induced only by WGE; similarly, that for KTI is greatly enhanced by WGE. While gene expression for PR-10 is induced by wounding, it is also strongly upregulated by WGE in a minimal wound background, suggesting a possibly independent effect of WGE. Finally, WGE also enhances the speed and magnitude of expression of GLU and WIN genes in all cell zones. Methyl jasmonate induces strong gene expression for KTI and the ethylene precursor, ACC, and jasmonic acid (JA) enhance that of GLU. The results are discussed in the context of the recently observed WGE- and JA-induced distal defense potentiation in soybean.

Effect of Treating Apple Trees with Acibenzolar-S-Methyl on Fire Blight and Expression of Pathogenesis-Related Protein Genes.

Acibenzolar-S-methyl (ASM, Actigard 50 WG), a synthetic inducer of systemic acquired resistance (SAR) and pathogenesis-related (PR) proteins, was evaluated for the control of fire blight on apple trees in the field and for PR protein gene expression in apple seedlings in the greenhouse. Expression of putative genes related to SAR induction was elevated in ASM-treated apple seedlings 2 to 7 days after treatment; levels of PR-1 and PR-8 RNA were increased 10-fold and PR-2 RNA was increased 100-fold in ASM-treated seedlings over levels in untreated seedlings. Spurs and shoots on Jonathan trees sprayed with ASM at 75 mg a.i./liter at pink and at weekly intervals thereafter had significantly less fire blight than untreated trees, both from natural infection and following artificial inoculation with the pathogen. Less fire blight was observed on trees sprayed weekly with ASM than on trees sprayed biweekly. The severity of fire blight on inoculated shoots of Fuji apple decreased with increasing rates of ASM (0 to 300 mg a.i./liter), and ASM combined with streptomycin showed enhanced activity over ASM at 75 mg a.i./liter alone. In general, ASM was not superior to streptomycin for fire blight control, but integrating a weekly schedule of ASM, preferably at 150 mg a.i./liter, with a schedule of streptomycin designed for blossom blight control appears promising for overall improvement in fire blight control.