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Agroinfiltration reduces ABA levels and suppresses Pseudomonas syringae-elicited salicylic acid production in Nicotiana tabacum.

Rico A, Bennett MH, Forcat S, Huang WE, Preston GM - PLoS ONE (2010)

Bottom Line: Agrobacterium tumefaciens strain GV3101 (pMP90) is widely used in transient gene expression assays, including assays to study pathogen effectors and plant disease resistance mechanisms.Pre-treatment with A. tumefaciens reduced ABA levels, P. syringae multiplication and P. syringae-elicited SA and ABA production, but promoted increased callose deposition.However, pre-treatment with A. tumefaciens did not suppress necrosis or SA production in leaves inoculated with the elicitor HrpZ.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.

ABSTRACT

Background: Agrobacterium tumefaciens strain GV3101 (pMP90) is widely used in transient gene expression assays, including assays to study pathogen effectors and plant disease resistance mechanisms. However, inoculation of A. tumefaciens GV3101 into Nicotiana tabacum (tobacco) leaves prior to infiltration with pathogenic and non-host strains of Pseudomonas syringae results in suppression of macroscopic symptoms when compared with leaves pre-treated with a buffer control.

Methodology/findings: To gain further insight into the mechanistic basis of symptom suppression by A. tumefaciens we examined the effect of pre-treatment with A. tumefaciens on the growth of P. syringae, the production of the plant signalling molecules salicylic acid (SA) and abscisic acid (ABA), and the presence of callose deposits. Pre-treatment with A. tumefaciens reduced ABA levels, P. syringae multiplication and P. syringae-elicited SA and ABA production, but promoted increased callose deposition. However, pre-treatment with A. tumefaciens did not suppress necrosis or SA production in leaves inoculated with the elicitor HrpZ.

Conclusions/significance: Collectively, these results show that inoculation of N. tabacum leaves with A. tumefaciens alters plant hormone levels and plant defence responses to P. syringae, and demonstrate that researchers should consider the impact of A. tumefaciens on plant signal transduction when using A. tumefaciens-mediated transient expression assays to investigate ABA-regulated processes or pathogenicity and plant defence mechanisms.

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Heat-killed A. tumefaciens suppresses P. syringae-elicited SA production to a lesser extent than live A. tumefaciens.A. The leaf shown was inoculated with A. tumefaciens GV3101 (AtGV3101 107 cfu/ml), heat-killed AtGV3101 (HK_At) or 10 mM MgCl2(AS) (Mg), followed by inoculation with P. syringae pv. tabaci 11528 (Pta), P. s. pv. tomato DC3000 (Pto) (105 cfu/ml) or 10 mM MgCl2 after 48 hours. The SA biosensor ADPWH-lux was inoculated into leaves 24 hours after infiltration with P. syringae. SA-induced luminescence was measured one hour after biosensor inoculation using a photon-counting camera. B. Absolute lux values were normalized against the infiltrated area. The bars show the average normalized luminescence values from three leaves. Error bars show standard deviation. General Linear Model (GLM) analysis revealed statistical differences between treatments (F = 81.2673; p<0.0001; df = 26). Means with the same letter were not significantly different at the 5% confidence level based on Tukey's HSD Test.
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pone-0008977-g003: Heat-killed A. tumefaciens suppresses P. syringae-elicited SA production to a lesser extent than live A. tumefaciens.A. The leaf shown was inoculated with A. tumefaciens GV3101 (AtGV3101 107 cfu/ml), heat-killed AtGV3101 (HK_At) or 10 mM MgCl2(AS) (Mg), followed by inoculation with P. syringae pv. tabaci 11528 (Pta), P. s. pv. tomato DC3000 (Pto) (105 cfu/ml) or 10 mM MgCl2 after 48 hours. The SA biosensor ADPWH-lux was inoculated into leaves 24 hours after infiltration with P. syringae. SA-induced luminescence was measured one hour after biosensor inoculation using a photon-counting camera. B. Absolute lux values were normalized against the infiltrated area. The bars show the average normalized luminescence values from three leaves. Error bars show standard deviation. General Linear Model (GLM) analysis revealed statistical differences between treatments (F = 81.2673; p<0.0001; df = 26). Means with the same letter were not significantly different at the 5% confidence level based on Tukey's HSD Test.

Mentions: Having shown that pre-treatment with AtGV3101 suppressed pathogen growth, symptom development, defence-associated cell death (HR) and SA production, we performed a series of experiments to define the conditions in which AtGV3101 was able to suppress P. syringae-elicited symptoms and SA production. Using the same experimental set up as described above, we observed that a suspension of heat-killed AtGV3101 retained some ability to suppress P. syringae-elicited SA, but was less able to suppress SA than live bacteria (Figure 3). This is in accordance with results published by Pruss and collaborators [17], which showed that heat-killed A. tumefaciens was less effective at protecting tobacco leaves from infection by TMV than live bacteria. Nevertheless, the observation that heat-killed bacteria retain some ability to suppress SA elicitation provides some support for the hypothesis that plant responses to A. tumefaciens PAMPs contribute to the effect of A. tumefaciens on P. syringae-plant interactions.


Agroinfiltration reduces ABA levels and suppresses Pseudomonas syringae-elicited salicylic acid production in Nicotiana tabacum.

Rico A, Bennett MH, Forcat S, Huang WE, Preston GM - PLoS ONE (2010)

Heat-killed A. tumefaciens suppresses P. syringae-elicited SA production to a lesser extent than live A. tumefaciens.A. The leaf shown was inoculated with A. tumefaciens GV3101 (AtGV3101 107 cfu/ml), heat-killed AtGV3101 (HK_At) or 10 mM MgCl2(AS) (Mg), followed by inoculation with P. syringae pv. tabaci 11528 (Pta), P. s. pv. tomato DC3000 (Pto) (105 cfu/ml) or 10 mM MgCl2 after 48 hours. The SA biosensor ADPWH-lux was inoculated into leaves 24 hours after infiltration with P. syringae. SA-induced luminescence was measured one hour after biosensor inoculation using a photon-counting camera. B. Absolute lux values were normalized against the infiltrated area. The bars show the average normalized luminescence values from three leaves. Error bars show standard deviation. General Linear Model (GLM) analysis revealed statistical differences between treatments (F = 81.2673; p<0.0001; df = 26). Means with the same letter were not significantly different at the 5% confidence level based on Tukey's HSD Test.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2813289&req=5

pone-0008977-g003: Heat-killed A. tumefaciens suppresses P. syringae-elicited SA production to a lesser extent than live A. tumefaciens.A. The leaf shown was inoculated with A. tumefaciens GV3101 (AtGV3101 107 cfu/ml), heat-killed AtGV3101 (HK_At) or 10 mM MgCl2(AS) (Mg), followed by inoculation with P. syringae pv. tabaci 11528 (Pta), P. s. pv. tomato DC3000 (Pto) (105 cfu/ml) or 10 mM MgCl2 after 48 hours. The SA biosensor ADPWH-lux was inoculated into leaves 24 hours after infiltration with P. syringae. SA-induced luminescence was measured one hour after biosensor inoculation using a photon-counting camera. B. Absolute lux values were normalized against the infiltrated area. The bars show the average normalized luminescence values from three leaves. Error bars show standard deviation. General Linear Model (GLM) analysis revealed statistical differences between treatments (F = 81.2673; p<0.0001; df = 26). Means with the same letter were not significantly different at the 5% confidence level based on Tukey's HSD Test.
Mentions: Having shown that pre-treatment with AtGV3101 suppressed pathogen growth, symptom development, defence-associated cell death (HR) and SA production, we performed a series of experiments to define the conditions in which AtGV3101 was able to suppress P. syringae-elicited symptoms and SA production. Using the same experimental set up as described above, we observed that a suspension of heat-killed AtGV3101 retained some ability to suppress P. syringae-elicited SA, but was less able to suppress SA than live bacteria (Figure 3). This is in accordance with results published by Pruss and collaborators [17], which showed that heat-killed A. tumefaciens was less effective at protecting tobacco leaves from infection by TMV than live bacteria. Nevertheless, the observation that heat-killed bacteria retain some ability to suppress SA elicitation provides some support for the hypothesis that plant responses to A. tumefaciens PAMPs contribute to the effect of A. tumefaciens on P. syringae-plant interactions.

Bottom Line: Agrobacterium tumefaciens strain GV3101 (pMP90) is widely used in transient gene expression assays, including assays to study pathogen effectors and plant disease resistance mechanisms.Pre-treatment with A. tumefaciens reduced ABA levels, P. syringae multiplication and P. syringae-elicited SA and ABA production, but promoted increased callose deposition.However, pre-treatment with A. tumefaciens did not suppress necrosis or SA production in leaves inoculated with the elicitor HrpZ.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.

ABSTRACT

Background: Agrobacterium tumefaciens strain GV3101 (pMP90) is widely used in transient gene expression assays, including assays to study pathogen effectors and plant disease resistance mechanisms. However, inoculation of A. tumefaciens GV3101 into Nicotiana tabacum (tobacco) leaves prior to infiltration with pathogenic and non-host strains of Pseudomonas syringae results in suppression of macroscopic symptoms when compared with leaves pre-treated with a buffer control.

Methodology/findings: To gain further insight into the mechanistic basis of symptom suppression by A. tumefaciens we examined the effect of pre-treatment with A. tumefaciens on the growth of P. syringae, the production of the plant signalling molecules salicylic acid (SA) and abscisic acid (ABA), and the presence of callose deposits. Pre-treatment with A. tumefaciens reduced ABA levels, P. syringae multiplication and P. syringae-elicited SA and ABA production, but promoted increased callose deposition. However, pre-treatment with A. tumefaciens did not suppress necrosis or SA production in leaves inoculated with the elicitor HrpZ.

Conclusions/significance: Collectively, these results show that inoculation of N. tabacum leaves with A. tumefaciens alters plant hormone levels and plant defence responses to P. syringae, and demonstrate that researchers should consider the impact of A. tumefaciens on plant signal transduction when using A. tumefaciens-mediated transient expression assays to investigate ABA-regulated processes or pathogenicity and plant defence mechanisms.

Show MeSH
Related in: MedlinePlus