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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 leaves of tomatoes with mycorrhizal colonization and pathogen infection. WT and mutant plants (35S::PS and spr2) of tomato 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 the PAL(A), LOX(B), (Pin2) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Transcript levels were quantified 18 (a), 65 (b), 100 (c), and 140 h (d) after pathogen inoculation. 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. Three tomato genotypes included: (1) WT: wild type plant; (2) 35S::PS: Prosystemin-overexpressing 35S::PS plant; (3) spr2: JA biosynthesis mutant plant. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences among treatments were tested at P = 0.05 by Tukey post hoc test.
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Figure 5: Transcripts of defense-related genes in leaves of tomatoes with mycorrhizal colonization and pathogen infection. WT and mutant plants (35S::PS and spr2) of tomato 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 the PAL(A), LOX(B), (Pin2) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Transcript levels were quantified 18 (a), 65 (b), 100 (c), and 140 h (d) after pathogen inoculation. 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. Three tomato genotypes included: (1) WT: wild type plant; (2) 35S::PS: Prosystemin-overexpressing 35S::PS plant; (3) spr2: JA biosynthesis mutant plant. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences among treatments were tested at P = 0.05 by Tukey post hoc test.

Mentions: Mycorrhizal pre-inoculation on 35S::PS and WT tomato plants resulted in strong induction of transcripts of defense-related genes (PAL, LOX, Pin2, PR1, PR2, and PR3) upon pathogen attack (treatment Fm+As) (Figures 5A–F). The highest induction of the six defense-related genes was found in the mycorrhizal 35S::PS plants. While no induction of PAL expression was found with pathogen inoculation alone (As) or AMF inoculation alone (Fm), dual inoculation with the AMF, and pathogen induced PAL 24.0- and 10.2-fold in 35S::PS and WT plants, respectively, 65 h after pathogen inoculation (Figure 5Ab). Similarly, AMF pre-inoculation and later pathogen infection induced PR1 18.3-, 6.5-, and 17.5-fold in 35S::PS plants as compared to that in treatments CK, As, and Fm, respectively, 100 h after pathogen inoculation (Figure 5Dc). Although pathogen infection alone induced PR1 transcripts in 35S::PS and WT plants, the induction was significantly lower relative to treatment Fm+As (Figure 5D). No induction was found in the spr2 plants in response to pathogen inoculation (As) or dual inoculation (Fm+As) (Figures 5A–F). Similar inductions of PR3 and Pin2 transcripts were observed in 35S::PS and WT plants, but there was no induction in the JA-deficient spr2 mutant (Figures 5C,F).


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 leaves of tomatoes with mycorrhizal colonization and pathogen infection. WT and mutant plants (35S::PS and spr2) of tomato 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 the PAL(A), LOX(B), (Pin2) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Transcript levels were quantified 18 (a), 65 (b), 100 (c), and 140 h (d) after pathogen inoculation. 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. Three tomato genotypes included: (1) WT: wild type plant; (2) 35S::PS: Prosystemin-overexpressing 35S::PS plant; (3) spr2: JA biosynthesis mutant plant. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences among treatments were tested at P = 0.05 by Tukey post hoc test.
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Figure 5: Transcripts of defense-related genes in leaves of tomatoes with mycorrhizal colonization and pathogen infection. WT and mutant plants (35S::PS and spr2) of tomato 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 the PAL(A), LOX(B), (Pin2) (C), pathogen-related proteins (PR1) (D), β-1,3-glucanase (basic type PR-2) (E), and chitinase (PR-3) (F). Transcript levels were quantified 18 (a), 65 (b), 100 (c), and 140 h (d) after pathogen inoculation. 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. Three tomato genotypes included: (1) WT: wild type plant; (2) 35S::PS: Prosystemin-overexpressing 35S::PS plant; (3) spr2: JA biosynthesis mutant plant. Values are means ± SE from three sets of independent experiments with three pots per treatment for each set of experiments. Significant differences among treatments were tested at P = 0.05 by Tukey post hoc test.
Mentions: Mycorrhizal pre-inoculation on 35S::PS and WT tomato plants resulted in strong induction of transcripts of defense-related genes (PAL, LOX, Pin2, PR1, PR2, and PR3) upon pathogen attack (treatment Fm+As) (Figures 5A–F). The highest induction of the six defense-related genes was found in the mycorrhizal 35S::PS plants. While no induction of PAL expression was found with pathogen inoculation alone (As) or AMF inoculation alone (Fm), dual inoculation with the AMF, and pathogen induced PAL 24.0- and 10.2-fold in 35S::PS and WT plants, respectively, 65 h after pathogen inoculation (Figure 5Ab). Similarly, AMF pre-inoculation and later pathogen infection induced PR1 18.3-, 6.5-, and 17.5-fold in 35S::PS plants as compared to that in treatments CK, As, and Fm, respectively, 100 h after pathogen inoculation (Figure 5Dc). Although pathogen infection alone induced PR1 transcripts in 35S::PS and WT plants, the induction was significantly lower relative to treatment Fm+As (Figure 5D). No induction was found in the spr2 plants in response to pathogen inoculation (As) or dual inoculation (Fm+As) (Figures 5A–F). Similar inductions of PR3 and Pin2 transcripts were observed in 35S::PS and WT plants, but there was no induction in the JA-deficient spr2 mutant (Figures 5C,F).

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