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Abscisic acid negatively interferes with basal defence of barley against Magnaporthe oryzae.

Ulferts S, Delventhal R, Splivallo R, Karlovsky P, Schaffrath U - BMC Plant Biol. (2015)

Bottom Line: Interestingly, endogenous ABA concentrations did not significantly change after infection of barley with M. oryzae.Our results revealed that elevated ABA levels led to a higher disease severity on barley leaves to M. oryzae.This supports earlier reports on the role of ABA in enhancing susceptibility of rice to the same pathogen and thereby demonstrates a host plant-independent function of this phytohormone in pathogenicity of monocotyledonous plants against M. oryzae.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Physiology, RWTH Aachen University, 52056, Aachen, Germany. sylvia.ulferts@gmx.de.

ABSTRACT

Background: Plant hormones are well known regulators which balance plant responses to abiotic and biotic stresses. We investigated the role of abscisic acid (ABA) in resistance of barley (Hordeum vulgare L.) against the plant pathogenic fungus Magnaporthe oryzae.

Results: Exogenous application of ABA prior to inoculation with M. oryzae led to more disease symptoms on barley leaves. This result contrasted the finding that ABA application enhances resistance of barley against the powdery mildew fungus. Microscopic analysis identified diminished penetration resistance as cause for enhanced susceptibility. Consistently, the barley mutant Az34, impaired in ABA biosynthesis, was less susceptible to infection by M. oryzae and displayed elevated penetration resistance as compared to the isogenic wild type cultivar Steptoe. Chemical complementation of Az34 mutant plants by exogenous application of ABA re-established disease severity to the wild type level. The role of ABA in susceptibility of barley against M. oryzae was corroborated by showing that ABA application led to increased disease severity in all barley cultivars under investigation except for the most susceptible cultivar Pallas. Interestingly, endogenous ABA concentrations did not significantly change after infection of barley with M. oryzae.

Conclusion: Our results revealed that elevated ABA levels led to a higher disease severity on barley leaves to M. oryzae. This supports earlier reports on the role of ABA in enhancing susceptibility of rice to the same pathogen and thereby demonstrates a host plant-independent function of this phytohormone in pathogenicity of monocotyledonous plants against M. oryzae.

No MeSH data available.


Related in: MedlinePlus

Effect of phytohormone application on the infection of barley withM. oryzae. Primary leaves of barley cultivar Ingrid were sprayed with the following solutions seven days after sawing: sodium salicylate (SA, 0.1 mM), 1-aminocyclopropane-1-carboxylic acid (ACC, 20 μM), indole-3-acetic acid (IAA, 20 μM), gibberellic acid (GA3, 20 μM), abscisic acid (ABA, 20 μM) or mock solution, respectively. One hour after treatment the plants were inoculated with conidia of M. oryzae isolate TH6772 (200,000 conidia mL−1). Representative leaves of each treatment seven days after inoculation are depicted in (A). Individual plant-fungus interaction sites were inspected microscopically on leaves harvested at 72 h p.i. (B) and assigned to categories as depicted in Figure 1. Bars represent means and standard deviations of four leaves with at least 100 interaction sites evaluated per leaf. Significant differences were determined for each category using One Way ANOVA (p ≤ 0.05) and marked by different letters. The experiment was repeated once with a similar result.
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Fig2: Effect of phytohormone application on the infection of barley withM. oryzae. Primary leaves of barley cultivar Ingrid were sprayed with the following solutions seven days after sawing: sodium salicylate (SA, 0.1 mM), 1-aminocyclopropane-1-carboxylic acid (ACC, 20 μM), indole-3-acetic acid (IAA, 20 μM), gibberellic acid (GA3, 20 μM), abscisic acid (ABA, 20 μM) or mock solution, respectively. One hour after treatment the plants were inoculated with conidia of M. oryzae isolate TH6772 (200,000 conidia mL−1). Representative leaves of each treatment seven days after inoculation are depicted in (A). Individual plant-fungus interaction sites were inspected microscopically on leaves harvested at 72 h p.i. (B) and assigned to categories as depicted in Figure 1. Bars represent means and standard deviations of four leaves with at least 100 interaction sites evaluated per leaf. Significant differences were determined for each category using One Way ANOVA (p ≤ 0.05) and marked by different letters. The experiment was repeated once with a similar result.

Mentions: Microscopic evaluation of the infection ofM. oryzaeon barley. Primary leaves of barley cultivar Ingrid were inoculated with a spore solution of M. oryzae isolate TH6772 (200,000 conidia mL−1) seven days after sowing. Leaves were harvested at 72 h p.i. and placed in 25% acetic acid in ethanol (v/v) until bleached. Thereafter, leaves were analyzed in water by bright field (A, B, D and E) or epi-fluorescence (C, F, G, H and I) microscopy. Category designations and labels correspond to the quantitative evaluation in Figures 2, 3 and 5C. app: appressorium; sechy: secondary hyphae; con: conidium; pap: papilla; gt: germ tube; epiHR: epidermal hypersensitive response; rmes: round-shaped mesophyll cells; cmes: collapsed mesophyll cells.


Abscisic acid negatively interferes with basal defence of barley against Magnaporthe oryzae.

Ulferts S, Delventhal R, Splivallo R, Karlovsky P, Schaffrath U - BMC Plant Biol. (2015)

Effect of phytohormone application on the infection of barley withM. oryzae. Primary leaves of barley cultivar Ingrid were sprayed with the following solutions seven days after sawing: sodium salicylate (SA, 0.1 mM), 1-aminocyclopropane-1-carboxylic acid (ACC, 20 μM), indole-3-acetic acid (IAA, 20 μM), gibberellic acid (GA3, 20 μM), abscisic acid (ABA, 20 μM) or mock solution, respectively. One hour after treatment the plants were inoculated with conidia of M. oryzae isolate TH6772 (200,000 conidia mL−1). Representative leaves of each treatment seven days after inoculation are depicted in (A). Individual plant-fungus interaction sites were inspected microscopically on leaves harvested at 72 h p.i. (B) and assigned to categories as depicted in Figure 1. Bars represent means and standard deviations of four leaves with at least 100 interaction sites evaluated per leaf. Significant differences were determined for each category using One Way ANOVA (p ≤ 0.05) and marked by different letters. The experiment was repeated once with a similar result.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4307682&req=5

Fig2: Effect of phytohormone application on the infection of barley withM. oryzae. Primary leaves of barley cultivar Ingrid were sprayed with the following solutions seven days after sawing: sodium salicylate (SA, 0.1 mM), 1-aminocyclopropane-1-carboxylic acid (ACC, 20 μM), indole-3-acetic acid (IAA, 20 μM), gibberellic acid (GA3, 20 μM), abscisic acid (ABA, 20 μM) or mock solution, respectively. One hour after treatment the plants were inoculated with conidia of M. oryzae isolate TH6772 (200,000 conidia mL−1). Representative leaves of each treatment seven days after inoculation are depicted in (A). Individual plant-fungus interaction sites were inspected microscopically on leaves harvested at 72 h p.i. (B) and assigned to categories as depicted in Figure 1. Bars represent means and standard deviations of four leaves with at least 100 interaction sites evaluated per leaf. Significant differences were determined for each category using One Way ANOVA (p ≤ 0.05) and marked by different letters. The experiment was repeated once with a similar result.
Mentions: Microscopic evaluation of the infection ofM. oryzaeon barley. Primary leaves of barley cultivar Ingrid were inoculated with a spore solution of M. oryzae isolate TH6772 (200,000 conidia mL−1) seven days after sowing. Leaves were harvested at 72 h p.i. and placed in 25% acetic acid in ethanol (v/v) until bleached. Thereafter, leaves were analyzed in water by bright field (A, B, D and E) or epi-fluorescence (C, F, G, H and I) microscopy. Category designations and labels correspond to the quantitative evaluation in Figures 2, 3 and 5C. app: appressorium; sechy: secondary hyphae; con: conidium; pap: papilla; gt: germ tube; epiHR: epidermal hypersensitive response; rmes: round-shaped mesophyll cells; cmes: collapsed mesophyll cells.

Bottom Line: Interestingly, endogenous ABA concentrations did not significantly change after infection of barley with M. oryzae.Our results revealed that elevated ABA levels led to a higher disease severity on barley leaves to M. oryzae.This supports earlier reports on the role of ABA in enhancing susceptibility of rice to the same pathogen and thereby demonstrates a host plant-independent function of this phytohormone in pathogenicity of monocotyledonous plants against M. oryzae.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Physiology, RWTH Aachen University, 52056, Aachen, Germany. sylvia.ulferts@gmx.de.

ABSTRACT

Background: Plant hormones are well known regulators which balance plant responses to abiotic and biotic stresses. We investigated the role of abscisic acid (ABA) in resistance of barley (Hordeum vulgare L.) against the plant pathogenic fungus Magnaporthe oryzae.

Results: Exogenous application of ABA prior to inoculation with M. oryzae led to more disease symptoms on barley leaves. This result contrasted the finding that ABA application enhances resistance of barley against the powdery mildew fungus. Microscopic analysis identified diminished penetration resistance as cause for enhanced susceptibility. Consistently, the barley mutant Az34, impaired in ABA biosynthesis, was less susceptible to infection by M. oryzae and displayed elevated penetration resistance as compared to the isogenic wild type cultivar Steptoe. Chemical complementation of Az34 mutant plants by exogenous application of ABA re-established disease severity to the wild type level. The role of ABA in susceptibility of barley against M. oryzae was corroborated by showing that ABA application led to increased disease severity in all barley cultivars under investigation except for the most susceptible cultivar Pallas. Interestingly, endogenous ABA concentrations did not significantly change after infection of barley with M. oryzae.

Conclusion: Our results revealed that elevated ABA levels led to a higher disease severity on barley leaves to M. oryzae. This supports earlier reports on the role of ABA in enhancing susceptibility of rice to the same pathogen and thereby demonstrates a host plant-independent function of this phytohormone in pathogenicity of monocotyledonous plants against M. oryzae.

No MeSH data available.


Related in: MedlinePlus