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Redundancy among phospholipase D isoforms in resistance triggered by recognition of the Pseudomonas syringae effector AvrRpm1 in Arabidopsis thaliana.

Johansson ON, Fahlberg P, Karimi E, Nilsson AK, Ellerström M, Andersson MX - Front Plant Sci (2014)

Bottom Line: Recognition of microbial effectors or their activity by plant resistance (R)-proteins triggers a second line of defense resulting in effector triggered immunity (ETI).However, repression of PLD dependent PA production by n-butanol strongly inhibited the HR following Pseudomonas syringae effector recognition.Thus, the effect of mutations of PLDs could become detectable, and the corresponding genes can be proposed to be involved in the HR.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology and Environmental Sciences, University of Gothenburg Gothenburg, Sweden.

ABSTRACT
Plants possess a highly sophisticated system for defense against microorganisms. So called MAMP (microbe-associated molecular patterns) triggered immunity (MTI) prevents the majority of non-adapted pathogens from causing disease. Adapted plant pathogens use secreted effector proteins to interfere with such signaling. Recognition of microbial effectors or their activity by plant resistance (R)-proteins triggers a second line of defense resulting in effector triggered immunity (ETI). The latter usually comprises the hypersensitive response (HR) which includes programmed cell death at the site of infection. Phospholipase D (PLD) mediated production of phosphatidic acid (PA) has been linked to both MTI and ETI in plants. Inhibition of PLD activity has been shown to attenuate MTI as well as ETI. In this study, we systematically tested single and double knockouts in all 12 genes encoding PLDs in Arabidopsis thaliana for effects on ETI and MTI. No single PLD could be linked to ETI triggered by recognition of effectors secreted by the bacterium Pseudomonas syringae. However, repression of PLD dependent PA production by n-butanol strongly inhibited the HR following Pseudomonas syringae effector recognition. In addition some pld mutants were more sensitive to n-butanol than wild type. Thus, the effect of mutations of PLDs could become detectable, and the corresponding genes can be proposed to be involved in the HR. Only knockout of PLDδ caused a loss of MTI-induced cell wall based defense against the non-host powdery mildew Erysiphe pisi. This is thus in stark contrast to the involvement of a multitude of PLD isoforms in the HR triggered by AvrRpm1 recognition.

No MeSH data available.


Related in: MedlinePlus

A high degree of redundancy in PLD genes in Arabidopsis involved in the HR in induced by AvrRpm1 recognition. Leaf discs were prepared from the indicated lines, infiltrated with Pst DC3000:AvrRpm1 and incubated in deionized water. Loss of cellular electrolytes was measured as the conductance of the bathing solution at the indicated time points. Col-0 and rpm1-3 are included in all experiments (A–D) together with the indicated subset of PLD knock out mutants. Average of six replicates and SD is shown. Lower case letters represent statistically significant different groups (one way ANOVA, p < 0.05) for the 6 h time point. The experiment was performed twice with similar results.
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Figure 3: A high degree of redundancy in PLD genes in Arabidopsis involved in the HR in induced by AvrRpm1 recognition. Leaf discs were prepared from the indicated lines, infiltrated with Pst DC3000:AvrRpm1 and incubated in deionized water. Loss of cellular electrolytes was measured as the conductance of the bathing solution at the indicated time points. Col-0 and rpm1-3 are included in all experiments (A–D) together with the indicated subset of PLD knock out mutants. Average of six replicates and SD is shown. Lower case letters represent statistically significant different groups (one way ANOVA, p < 0.05) for the 6 h time point. The experiment was performed twice with similar results.

Mentions: We previously tested a panel of PLD mutants for effects on cell wall based resistance to barley powdery mildew and found that PLDδ was involved in the MAMP triggered signaling involved in the defense reaction (Pinosa et al., 2013). However, as effector triggered resistance differs significantly from MAMP triggered defense responses, we tested if the PLD-mediated effect on could be attributed to any particular of the 12 PLD genes in the Arabidopsis genome. Single (Figure 3), double and triple (Figure 4) pld T-DNA mutants (Pinosa et al., 2013) were assayed for HR induced after infiltration with Pst DC3000:AvrRpm1. This revealed no clear reduction in HR induced ion leakage for any of the tested mutants compared to wild type. The pldγ1 and pldγ3 mutants appeared to demonstrate a slightly elevated cell death response following AvrRpm1 recognition (Figure 3D). Taken together, this suggests that there is a high degree of genetic redundancy among the PLD isoforms activated during HR induced by AvrRpm1 recognition.


Redundancy among phospholipase D isoforms in resistance triggered by recognition of the Pseudomonas syringae effector AvrRpm1 in Arabidopsis thaliana.

Johansson ON, Fahlberg P, Karimi E, Nilsson AK, Ellerström M, Andersson MX - Front Plant Sci (2014)

A high degree of redundancy in PLD genes in Arabidopsis involved in the HR in induced by AvrRpm1 recognition. Leaf discs were prepared from the indicated lines, infiltrated with Pst DC3000:AvrRpm1 and incubated in deionized water. Loss of cellular electrolytes was measured as the conductance of the bathing solution at the indicated time points. Col-0 and rpm1-3 are included in all experiments (A–D) together with the indicated subset of PLD knock out mutants. Average of six replicates and SD is shown. Lower case letters represent statistically significant different groups (one way ANOVA, p < 0.05) for the 6 h time point. The experiment was performed twice with similar results.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230166&req=5

Figure 3: A high degree of redundancy in PLD genes in Arabidopsis involved in the HR in induced by AvrRpm1 recognition. Leaf discs were prepared from the indicated lines, infiltrated with Pst DC3000:AvrRpm1 and incubated in deionized water. Loss of cellular electrolytes was measured as the conductance of the bathing solution at the indicated time points. Col-0 and rpm1-3 are included in all experiments (A–D) together with the indicated subset of PLD knock out mutants. Average of six replicates and SD is shown. Lower case letters represent statistically significant different groups (one way ANOVA, p < 0.05) for the 6 h time point. The experiment was performed twice with similar results.
Mentions: We previously tested a panel of PLD mutants for effects on cell wall based resistance to barley powdery mildew and found that PLDδ was involved in the MAMP triggered signaling involved in the defense reaction (Pinosa et al., 2013). However, as effector triggered resistance differs significantly from MAMP triggered defense responses, we tested if the PLD-mediated effect on could be attributed to any particular of the 12 PLD genes in the Arabidopsis genome. Single (Figure 3), double and triple (Figure 4) pld T-DNA mutants (Pinosa et al., 2013) were assayed for HR induced after infiltration with Pst DC3000:AvrRpm1. This revealed no clear reduction in HR induced ion leakage for any of the tested mutants compared to wild type. The pldγ1 and pldγ3 mutants appeared to demonstrate a slightly elevated cell death response following AvrRpm1 recognition (Figure 3D). Taken together, this suggests that there is a high degree of genetic redundancy among the PLD isoforms activated during HR induced by AvrRpm1 recognition.

Bottom Line: Recognition of microbial effectors or their activity by plant resistance (R)-proteins triggers a second line of defense resulting in effector triggered immunity (ETI).However, repression of PLD dependent PA production by n-butanol strongly inhibited the HR following Pseudomonas syringae effector recognition.Thus, the effect of mutations of PLDs could become detectable, and the corresponding genes can be proposed to be involved in the HR.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology and Environmental Sciences, University of Gothenburg Gothenburg, Sweden.

ABSTRACT
Plants possess a highly sophisticated system for defense against microorganisms. So called MAMP (microbe-associated molecular patterns) triggered immunity (MTI) prevents the majority of non-adapted pathogens from causing disease. Adapted plant pathogens use secreted effector proteins to interfere with such signaling. Recognition of microbial effectors or their activity by plant resistance (R)-proteins triggers a second line of defense resulting in effector triggered immunity (ETI). The latter usually comprises the hypersensitive response (HR) which includes programmed cell death at the site of infection. Phospholipase D (PLD) mediated production of phosphatidic acid (PA) has been linked to both MTI and ETI in plants. Inhibition of PLD activity has been shown to attenuate MTI as well as ETI. In this study, we systematically tested single and double knockouts in all 12 genes encoding PLDs in Arabidopsis thaliana for effects on ETI and MTI. No single PLD could be linked to ETI triggered by recognition of effectors secreted by the bacterium Pseudomonas syringae. However, repression of PLD dependent PA production by n-butanol strongly inhibited the HR following Pseudomonas syringae effector recognition. In addition some pld mutants were more sensitive to n-butanol than wild type. Thus, the effect of mutations of PLDs could become detectable, and the corresponding genes can be proposed to be involved in the HR. Only knockout of PLDδ caused a loss of MTI-induced cell wall based defense against the non-host powdery mildew Erysiphe pisi. This is thus in stark contrast to the involvement of a multitude of PLD isoforms in the HR triggered by AvrRpm1 recognition.

No MeSH data available.


Related in: MedlinePlus