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Chitosan oligosaccharide induces resistance to Tobacco mosaic virus in Arabidopsis via the salicylic acid-mediated signalling pathway.

ABSTRACT: Chitosan is one of the most abundant carbohydrate biopolymers in the world, and chitosan oligosaccharide (COS), which is prepared from chitosan, is a plant immunity regulator. The present study aimed to validate the effect of COS on inducing resistance to tobacco mosaic virus (TMV) in Arabidopsis and to investigate the potential defence-related signalling pathways involved. Optimal conditions for the induction of TMV resistance in Arabidopsis were COS pretreatment at 50?mg/L for 1 day prior to inoculation with TMV. Multilevel indices, including phenotype data, and TMV coat protein expression, revealed that COS induced TMV resistance in wild-type and jasmonic acid pathway- deficient (jar1) Arabidopsis plants, but not in salicylic acid pathway deficient (NahG) Arabidopsis plants. Quantitative-PCR and analysis of phytohormone levels confirmed that COS pretreatment enhanced the expression of the defence-related gene PR1, which is a marker of salicylic acid signalling pathway, and increased the amount of salicylic acid in WT and jar1, but not in NahG plants. Taken together, these results confirm that COS induces TMV resistance in Arabidopsis via activation of the salicylic acid signalling pathway.

SUBMITTER: Jia X

PROVIDER: S-EPMC4870575 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Chitosan oligosaccharide induces resistance to Tobacco mosaic virus in Arabidopsis via the salicylic acid-mediated signalling pathway.

Jia Xiaochen X Meng Qingshan Q Zeng Haihong H Wang Wenxia W Yin Heng H

Scientific reports 20160518

Chitosan is one of the most abundant carbohydrate biopolymers in the world, and chitosan oligosaccharide (COS), which is prepared from chitosan, is a plant immunity regulator. The present study aimed to validate the effect of COS on inducing resistance to tobacco mosaic virus (TMV) in Arabidopsis and to investigate the potential defence-related signalling pathways involved. Optimal conditions for the induction of TMV resistance in Arabidopsis were COS pretreatment at 50 mg/L for 1 day prior to i ...[more]

PMID: 27189192

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Project description:Earlier studies showed that the artificial elevation of endogenous glutathione (GSH) contents can markedly increase the resistance of plants against different viruses. On the other hand, salicylic acid (SA)-deficient NahG plants display enhanced susceptibility to viral infections. In the present study, the biochemical mechanisms underlying GSH-induced resistance were investigated in various tobacco biotypes displaying markedly different GSH and SA levels. The endogenous GSH levels of Nicotiana tabacum cv. Xanthi NN and N. tabacum cv. Xanthi NN NahG tobacco leaves were increased by infiltration of exogenous GSH or its synthetic precursor R-2-oxo-4-thiazolidine-carboxylic acid (OTC). Alternatively, we also used tobacco lines containing high GSH levels due to transgenes encoding critical enzymes for cysteine and GSH biosynthesis. We crossed Xanthi NN and NahG tobaccos with the GSH overproducer transgenic tobacco lines in order to obtain F1 progenies with increased levels of GSH and decreased levels of SA. We demonstrated that in SA-deficient NahG tobacco the elevation of in planta GSH and GSSG levels either by exogenous GSH or by crossing with glutathione overproducing plants confers enhanced resistance to Tobacco mosaic virus (TMV) manifested as both reduced symptoms (i.e. suppression of hypersensitive-type localized necrosis) and lower virus titers. The beneficial effects of elevated GSH on TMV resistance was markedly stronger in NahG than in Xanthi NN leaves. Infiltration of exogenous GSH and OTC or crossing with GSH overproducer tobacco lines resulted in a substantial rise of bound SA and to a lesser extent of free SA levels in tobacco, especially following TMV infection. Significant increases in expression of pathogenesis related (NtPR-1a, and NtPRB-1b), and glutathione S-transferase (NtGSTtau, and NtGSTphi) genes were evident in TMV-inoculated leaves in later stages of pathogenesis. However, the highest levels of defense gene expression were associated with SA-deficiency, rather than enhanced TMV resistance. In summary, elevated levels of glutathione in TMV-infected tobacco can compensate for SA deficiency to maintain virus resistance. Our results suggest that glutathione-induced redox changes are important components of antiviral signaling in tobacco.

Project description:Abstract: Chemogenomic fitness assays were combined with a transcriptome analysis to understand both the mode of action and the mechanisms of resistance to Chitosan oligosaccharides (COS). COS are deacetylated chitin compounds, with antimicrobial properties, that are presumed to act by disrupting the cell membrane. The fitness assays identified 39 yeast deletion strains sensitive to COS and 21 suppressors of COS sensitivity. The genes identified encode membrane proteins and members of the protein degradation/ proteosome pathway. The transcriptomes of wild-type and five suppressor strains overexpressing ARL1, BCK2, ERG24, MSG5, or RBA50, were analyzed in the presence and absence of COS. The COS-induced transcriptional response is distinct from previously described environmental stress responses (i.e. thermal, salt, osmotic and oxidative stress) and furthermore, treatment with environmental stressors does not provide resistance to COS. Some of the up-regulated transcripts in the suppressor overexpressing strains exposed to COS included genes involved in transcription, cell cycle, stress response and the RAS signal transduction pathway. Down-regulated transcripts included those encoding protein folding components, and respiratory chain proteins. Overexpression of the ARL1 gene, a member of the Ras superfamily that regulates membrane trafficking, provides protection against COS-induced cell membrane permeability and damage. We found that the ARL1 COS-resistant over-expression strain was as sensitive to amphotericin B, fluconazole and terbinafine as the wild-type (vector control). The gene targets of COS identified in this study suggest that COS’s mechanism of action is different from other commonly studied fungicides, suggesting that COS may be an effective fungicide for drug-resistant fungal pathogens. We selected the 5 overexpressing strains based on the characteristics of the genes. ARL1, encoding a GTPase and is involved in membrane trafficking, was selected since it was observed in the HIP-HOP assay as a sensitive homozygous deletion strain and in the MSP assay as multicopy suppressor. The rest of selected overexpressing strains were BCK2 and MSG5, involved in cell integrity pathways, ERG24 in ergosterol synthesis, and RBA50 in transcription. BCK2 is a Ser-Thr rich protein with protein kinase C activity that acts in signal transduction. Overexpression of BCK2 can rescue defects in yeast cwh43Δ, which displays several cell wall defects [29]. BCK2 overexpression also can suppress a cell lysis defect of mpk1Δ and pck1Δ [30]. MSG5 is also involved in signal transduction. This gene encodes a protein phosphatase involved in cell cycle control through the dephosphorylation of MAPK and is indispensable for restricting the signaling by the cell integrity pathway in yeast [31]. The inhibition of MAPK signaling leads to inhibition of cell differentiation and cell division [32]. The functions of ARL1 and ERG24 and their potential roles in chitosan resistance will be described in more detail in the Discussion. To gain a further understanding on the mode of action and mechanisms of resistance to COS, we performed a transcriptome analysis of the above mentioned five overexpressing strains known to increase resistance to COS-5.44. Each overexpressing strain and the wild type (vector control) were treated with COS-5.44 and RNAs isolated from both treated and untreated cells. The RNAs were converted to labeled cDNA and hybridized to NimbleGen expression microarrays (see Methods).

Project description:Abstract: Chemogenomic fitness assays were combined with a transcriptome analysis to understand both the mode of action and the mechanisms of resistance to Chitosan oligosaccharides (COS). COS are deacetylated chitin compounds, with antimicrobial properties, that are presumed to act by disrupting the cell membrane. The fitness assays identified 39 yeast deletion strains sensitive to COS and 21 suppressors of COS sensitivity. The genes identified encode membrane proteins and members of the protein degradation/ proteosome pathway. The transcriptomes of wild-type and five suppressor strains overexpressing ARL1, BCK2, ERG24, MSG5, or RBA50, were analyzed in the presence and absence of COS. The COS-induced transcriptional response is distinct from previously described environmental stress responses (i.e. thermal, salt, osmotic and oxidative stress) and furthermore, treatment with environmental stressors does not provide resistance to COS. Some of the up-regulated transcripts in the suppressor overexpressing strains exposed to COS included genes involved in transcription, cell cycle, stress response and the RAS signal transduction pathway. Down-regulated transcripts included those encoding protein folding components, and respiratory chain proteins. Overexpression of the ARL1 gene, a member of the Ras superfamily that regulates membrane trafficking, provides protection against COS-induced cell membrane permeability and damage. We found that the ARL1 COS-resistant over-expression strain was as sensitive to amphotericin B, fluconazole and terbinafine as the wild-type (vector control). The gene targets of COS identified in this study suggest that COSM-bM-^@M-^Ys mechanism of action is different from other commonly studied fungicides, suggesting that COS may be an effective fungicide for drug-resistant fungal pathogens. We selected the 5 overexpressing strains based on the characteristics of the genes. ARL1, encoding a GTPase and is involved in membrane trafficking, was selected since it was observed in the HIP-HOP assay as a sensitive homozygous deletion strain and in the MSP assay as multicopy suppressor. The rest of selected overexpressing strains were BCK2 and MSG5, involved in cell integrity pathways, ERG24 in ergosterol synthesis, and RBA50 in transcription. BCK2 is a Ser-Thr rich protein with protein kinase C activity that acts in signal transduction. Overexpression of BCK2 can rescue defects in yeast cwh43M-NM-^T, which displays several cell wall defects [29]. BCK2 overexpression also can suppress a cell lysis defect of mpk1M-NM-^T and pck1M-NM-^T [30]. MSG5 is also involved in signal transduction. This gene encodes a protein phosphatase involved in cell cycle control through the dephosphorylation of MAPK and is indispensable for restricting the signaling by the cell integrity pathway in yeast [31]. The inhibition of MAPK signaling leads to inhibition of cell differentiation and cell division [32]. The functions of ARL1 and ERG24 and their potential roles in chitosan resistance will be described in more detail in the Discussion. To gain a further understanding on the mode of action and mechanisms of resistance to COS, we performed a transcriptome analysis of the above mentioned five overexpressing strains known to increase resistance to COS-5.44. Each overexpressing strain and the wild type (vector control) were treated with COS-5.44 and RNAs isolated from both treated and untreated cells. The RNAs were converted to labeled cDNA and hybridized to NimbleGen expression microarrays (see Methods). Three cDNA biological replicates either with or without a 60 minutes exposure to COS-5.44 for each of the five overexpressing strains as well as an untransformed wild type BY4743 cells (vector control; for a total of 36 samples) were hybridized to NimbleGen 4X72k microarrays (Roche NimbleGen, Inc. Design ID A6186-00-01, TI4932 60mer expr X4).

Dataset Information

Chitosan oligosaccharide induces resistance to Tobacco mosaic virus in Arabidopsis via the salicylic acid-mediated signalling pathway.

Publications

Chitosan oligosaccharide induces resistance to Tobacco mosaic virus in Arabidopsis via the salicylic acid-mediated signalling pathway.

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