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Enhanced tomato disease resistance primed by arbuscular mycorrhizal fungus.

Song Y, Chen D, Lu K, Sun Z, Zeng R - Front Plant Sci (2015)

Bottom Line: Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense.Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants.However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou China ; State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources, College of Agriculture, South China Agricultural University, Guangzhou China.

ABSTRACT
Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance.

No MeSH data available.


Related in: MedlinePlus

Transcripts of defense-related genes in tomato leaves in response to mycorrhizal colonization and pathogen infection. The tomates were pre-inoculated with mycorrhizal fungus Funneliformis mosseae and later inoculated with A. solani, the causal agent of early blight disease of tomato. Quantitative real time RT-PCR was used to detect the transcripts of six defense-related genes encoding PAL(A), LOX(B), allene oxide cyclase (AOC) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Four treatments included: (1) CK: control plants without pathogen and mycorrhizal inoculation; (2) As: plants inoculated with A. solani only; (3) Fm: plants inoculated with F. mosseae only; (4) Fm+As: plants inoculated with both F. mosseae and A. solani. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences (P < 0.05 using Tukey post hoc test) among treatments in a group are indicated by different letters above bars.
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Figure 3: Transcripts of defense-related genes in tomato leaves in response to mycorrhizal colonization and pathogen infection. The tomates were pre-inoculated with mycorrhizal fungus Funneliformis mosseae and later inoculated with A. solani, the causal agent of early blight disease of tomato. Quantitative real time RT-PCR was used to detect the transcripts of six defense-related genes encoding PAL(A), LOX(B), allene oxide cyclase (AOC) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Four treatments included: (1) CK: control plants without pathogen and mycorrhizal inoculation; (2) As: plants inoculated with A. solani only; (3) Fm: plants inoculated with F. mosseae only; (4) Fm+As: plants inoculated with both F. mosseae and A. solani. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences (P < 0.05 using Tukey post hoc test) among treatments in a group are indicated by different letters above bars.

Mentions: To determine whether mycorrhizal colonization enhances the disease resistance and defense response by inducing transcription of defense-related genes (Pozo et al., 2005), the expression patterns of the six genes (PAL, LOX, AOC (encoding allene oxide cyclase for JA biosynthesis), PR1, PR2, and PR3) were analyzed by using real-time RT-PCR from tomato leaves 18, 65, 100, and 140 h post pathogen inoculation. Mycorrhizal pre-inoculation of tomato plants with F. mosseae and later pathogen inoculation with A. solani (treatment Fm+As) induced accumulation of PAL, LOX, AOC, PR1, PR2, and PR3 transcripts over basal levels present in the leaves of un- inoculated control (CK), sole A. solani inoculation (As), and F. mosseae colonization (Fm) treatments 18, 65, 100, and 140 h after pathogen inoculation (Figure 3). The expression levels of PAL, LOX, and AOC were induced approximately 3.0, 7.1, and 18.8-fold at 100 h, and by 4.1, 5.3, and 5.8-fold at 140 h post pathogen inoculation, respectively, in response to dual inoculation with the AMF and the pathogen (Fm+As) relative to the non-mycorrhizal control (CK) (Figures 3A–C). Mycorrhizal pre-colonization induced transcripts of PR1, PR2, and PR3 by 20.4, 35.5, and 47.7-fold at 65 h, by 8.0, 37.7, and 22.9-fold at 100 h, respectively (CK) (Figures 3D–F). Pathogen infection alone (treatment As) induced transcripts of the six genes in the leaves of non-preinoculated tomato plants, but the induction was much less and slower compared with that in mycorrhizal and pathogen-infected plants (treatment Fm+As). Mycorrhizal colonization (treatment Fm) alone did not induce gene expression of PAL and PR3 (Figures 3A,F). Although sole mycorrhization up-regulated transcripts of PR1, PR2, and AOC at 100 and 140 h, the induction was even weaker than that by pathogen infection.


Enhanced tomato disease resistance primed by arbuscular mycorrhizal fungus.

Song Y, Chen D, Lu K, Sun Z, Zeng R - Front Plant Sci (2015)

Transcripts of defense-related genes in tomato leaves in response to mycorrhizal colonization and pathogen infection. The tomates were pre-inoculated with mycorrhizal fungus Funneliformis mosseae and later inoculated with A. solani, the causal agent of early blight disease of tomato. Quantitative real time RT-PCR was used to detect the transcripts of six defense-related genes encoding PAL(A), LOX(B), allene oxide cyclase (AOC) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Four treatments included: (1) CK: control plants without pathogen and mycorrhizal inoculation; (2) As: plants inoculated with A. solani only; (3) Fm: plants inoculated with F. mosseae only; (4) Fm+As: plants inoculated with both F. mosseae and A. solani. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences (P < 0.05 using Tukey post hoc test) among treatments in a group are indicated by different letters above bars.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
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Figure 3: Transcripts of defense-related genes in tomato leaves in response to mycorrhizal colonization and pathogen infection. The tomates were pre-inoculated with mycorrhizal fungus Funneliformis mosseae and later inoculated with A. solani, the causal agent of early blight disease of tomato. Quantitative real time RT-PCR was used to detect the transcripts of six defense-related genes encoding PAL(A), LOX(B), allene oxide cyclase (AOC) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Four treatments included: (1) CK: control plants without pathogen and mycorrhizal inoculation; (2) As: plants inoculated with A. solani only; (3) Fm: plants inoculated with F. mosseae only; (4) Fm+As: plants inoculated with both F. mosseae and A. solani. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences (P < 0.05 using Tukey post hoc test) among treatments in a group are indicated by different letters above bars.
Mentions: To determine whether mycorrhizal colonization enhances the disease resistance and defense response by inducing transcription of defense-related genes (Pozo et al., 2005), the expression patterns of the six genes (PAL, LOX, AOC (encoding allene oxide cyclase for JA biosynthesis), PR1, PR2, and PR3) were analyzed by using real-time RT-PCR from tomato leaves 18, 65, 100, and 140 h post pathogen inoculation. Mycorrhizal pre-inoculation of tomato plants with F. mosseae and later pathogen inoculation with A. solani (treatment Fm+As) induced accumulation of PAL, LOX, AOC, PR1, PR2, and PR3 transcripts over basal levels present in the leaves of un- inoculated control (CK), sole A. solani inoculation (As), and F. mosseae colonization (Fm) treatments 18, 65, 100, and 140 h after pathogen inoculation (Figure 3). The expression levels of PAL, LOX, and AOC were induced approximately 3.0, 7.1, and 18.8-fold at 100 h, and by 4.1, 5.3, and 5.8-fold at 140 h post pathogen inoculation, respectively, in response to dual inoculation with the AMF and the pathogen (Fm+As) relative to the non-mycorrhizal control (CK) (Figures 3A–C). Mycorrhizal pre-colonization induced transcripts of PR1, PR2, and PR3 by 20.4, 35.5, and 47.7-fold at 65 h, by 8.0, 37.7, and 22.9-fold at 100 h, respectively (CK) (Figures 3D–F). Pathogen infection alone (treatment As) induced transcripts of the six genes in the leaves of non-preinoculated tomato plants, but the induction was much less and slower compared with that in mycorrhizal and pathogen-infected plants (treatment Fm+As). Mycorrhizal colonization (treatment Fm) alone did not induce gene expression of PAL and PR3 (Figures 3A,F). Although sole mycorrhization up-regulated transcripts of PR1, PR2, and AOC at 100 and 140 h, the induction was even weaker than that by pathogen infection.

Bottom Line: Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense.Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants.However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou China ; State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources, College of Agriculture, South China Agricultural University, Guangzhou China.

ABSTRACT
Roots of most terrestrial plants form symbiotic associations (mycorrhiza) with soil- borne arbuscular mycorrhizal fungi (AMF). Many studies show that mycorrhizal colonization enhances plant resistance against pathogenic fungi. However, the mechanism of mycorrhiza-induced disease resistance remains equivocal. In this study, we found that mycorrhizal inoculation with AMF Funneliformis mosseae significantly alleviated tomato (Solanum lycopersicum Mill.) early blight disease caused by Alternaria solani Sorauer. AMF pre-inoculation led to significant increases in activities of β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) in tomato leaves upon pathogen inoculation. Mycorrhizal inoculation alone did not influence the transcripts of most genes tested. However, pathogen attack on AMF-inoculated plants provoked strong defense responses of three genes encoding pathogenesis-related proteins, PR1, PR2, and PR3, as well as defense-related genes LOX, AOC, and PAL, in tomato leaves. The induction of defense responses in AMF pre-inoculated plants was much higher and more rapid than that in un-inoculated plants in present of pathogen infection. Three tomato genotypes: a Castlemart wild-type (WT) plant, a jasmonate (JA) biosynthesis mutant (spr2), and a prosystemin-overexpressing 35S::PS plant were used to examine the role of the JA signaling pathway in AMF-primed disease defense. Pathogen infection on mycorrhizal 35S::PS plants led to higher induction of defense-related genes and enzymes relative to WT plants. However, pathogen infection did not induce these genes and enzymes in mycorrhizal spr2 mutant plants. Bioassays showed that 35S::PS plants were more resistant and spr2 plants were more susceptible to early blight compared with WT plants. Our finding indicates that mycorrhizal colonization enhances tomato resistance to early blight by priming systemic defense response, and the JA signaling pathway is essential for mycorrhiza-primed disease resistance.

No MeSH data available.


Related in: MedlinePlus