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Induced systemic resistance against Botrytis cinerea by Micromonospora strains isolated from root nodules.

Martínez-Hidalgo P, García JM, Pozo MJ - Front Microbiol (2015)

Bottom Line: This induced systemic resistance, confirmed in different tomato cultivars, is long lasting.The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen.The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Genetics, University of Salamanca Salamanca, Spain ; Unidad Asociada USAL-CSIC "Interacción Planta-Microorganismo" Salamanca, Spain.

ABSTRACT
Micromonospora is a Gram positive bacterium that can be isolated from nitrogen fixing nodules from healthy leguminous plants, where they could be beneficial to the plant. Their plant growth promoting activity in legume and non-legume plants has been previously demonstrated. The present study explores the ability of Micromonospora strains to control fungal pathogens and to stimulate plant immunity. Micromonospora strains isolated from surface sterilized nodules of alfalfa showed in vitro antifungal activity against several pathogenic fungi. Moreover, root inoculation of tomato plants with these Micromonospora strains effectively reduced leaf infection by the fungal pathogen Botrytis cinerea, despite spatial separation between both microorganisms. This induced systemic resistance, confirmed in different tomato cultivars, is long lasting. Gene expression analyses evidenced that Micromonospora stimulates the plant capacity to activate defense mechanisms upon pathogen attack. The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen. The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation. In conclusion, nodule isolated Micromonospora strains should be considered excellent candidates as biocontrol agents as they combine both direct antifungal activity against plant pathogens and the ability to prime plant immunity.

No MeSH data available.


Related in: MedlinePlus

Expression levels of the defense related genes PR1, LoxA, and PinII in leaves of tomato plants. Relative expression levels for PR1, LoxA, and PinII were determined by qPCR and normalized against the constitutive SlEF (tomato elongation factor α). Control: uninoculated, unchallenged plants; pr18c: plants inoculated with Micromonospora strain ALFpr18c; Botrytis: uninoculated plants challenged with B. cinerea; pr18c+Botrytis: plants previously inoculated with Micromonospora strain ALFpr18c and challenged with B. cinerea. Micromonospora inoculation was performed at transplanting, a month before infection with Botrytis. Data not sharing a common letter are significantly different according to Fisher’s protected LSD test at P ≥ 0.05.
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Figure 3: Expression levels of the defense related genes PR1, LoxA, and PinII in leaves of tomato plants. Relative expression levels for PR1, LoxA, and PinII were determined by qPCR and normalized against the constitutive SlEF (tomato elongation factor α). Control: uninoculated, unchallenged plants; pr18c: plants inoculated with Micromonospora strain ALFpr18c; Botrytis: uninoculated plants challenged with B. cinerea; pr18c+Botrytis: plants previously inoculated with Micromonospora strain ALFpr18c and challenged with B. cinerea. Micromonospora inoculation was performed at transplanting, a month before infection with Botrytis. Data not sharing a common letter are significantly different according to Fisher’s protected LSD test at P ≥ 0.05.

Mentions: To understand the mechanism behind this long term induced resistance, and to determine what defense signaling pathways were involved, we compared the response against B. cinerea in plants inoculated or not with the strain Micromonospora sp. ALFpr18c 30 days before the challenge with the pathogen. Plant defense responses to Botrytis are known to depend on the interplay between SA and JA dependent responses, and those regulated by JA have been proposed as the major players in resistance (El Oirdi et al., 2011). Accordingly, we monitored the expression levels of well-characterized marker genes for both signaling pathways in leaves from the different treatments. Non-challenged plants showed no differences in the expression levels of any of the marker genes analyzed regardless of the presence of Micromonospora sp. (Figure 3). In contrast, important differences were found in the transcription levels of marker genes from both pathways between non-inoculated plants and plants preinoculated with Micromonospora spp. upon challenge with B. cinerea (Figure 3).


Induced systemic resistance against Botrytis cinerea by Micromonospora strains isolated from root nodules.

Martínez-Hidalgo P, García JM, Pozo MJ - Front Microbiol (2015)

Expression levels of the defense related genes PR1, LoxA, and PinII in leaves of tomato plants. Relative expression levels for PR1, LoxA, and PinII were determined by qPCR and normalized against the constitutive SlEF (tomato elongation factor α). Control: uninoculated, unchallenged plants; pr18c: plants inoculated with Micromonospora strain ALFpr18c; Botrytis: uninoculated plants challenged with B. cinerea; pr18c+Botrytis: plants previously inoculated with Micromonospora strain ALFpr18c and challenged with B. cinerea. Micromonospora inoculation was performed at transplanting, a month before infection with Botrytis. Data not sharing a common letter are significantly different according to Fisher’s protected LSD test at P ≥ 0.05.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4556977&req=5

Figure 3: Expression levels of the defense related genes PR1, LoxA, and PinII in leaves of tomato plants. Relative expression levels for PR1, LoxA, and PinII were determined by qPCR and normalized against the constitutive SlEF (tomato elongation factor α). Control: uninoculated, unchallenged plants; pr18c: plants inoculated with Micromonospora strain ALFpr18c; Botrytis: uninoculated plants challenged with B. cinerea; pr18c+Botrytis: plants previously inoculated with Micromonospora strain ALFpr18c and challenged with B. cinerea. Micromonospora inoculation was performed at transplanting, a month before infection with Botrytis. Data not sharing a common letter are significantly different according to Fisher’s protected LSD test at P ≥ 0.05.
Mentions: To understand the mechanism behind this long term induced resistance, and to determine what defense signaling pathways were involved, we compared the response against B. cinerea in plants inoculated or not with the strain Micromonospora sp. ALFpr18c 30 days before the challenge with the pathogen. Plant defense responses to Botrytis are known to depend on the interplay between SA and JA dependent responses, and those regulated by JA have been proposed as the major players in resistance (El Oirdi et al., 2011). Accordingly, we monitored the expression levels of well-characterized marker genes for both signaling pathways in leaves from the different treatments. Non-challenged plants showed no differences in the expression levels of any of the marker genes analyzed regardless of the presence of Micromonospora sp. (Figure 3). In contrast, important differences were found in the transcription levels of marker genes from both pathways between non-inoculated plants and plants preinoculated with Micromonospora spp. upon challenge with B. cinerea (Figure 3).

Bottom Line: This induced systemic resistance, confirmed in different tomato cultivars, is long lasting.The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen.The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Genetics, University of Salamanca Salamanca, Spain ; Unidad Asociada USAL-CSIC "Interacción Planta-Microorganismo" Salamanca, Spain.

ABSTRACT
Micromonospora is a Gram positive bacterium that can be isolated from nitrogen fixing nodules from healthy leguminous plants, where they could be beneficial to the plant. Their plant growth promoting activity in legume and non-legume plants has been previously demonstrated. The present study explores the ability of Micromonospora strains to control fungal pathogens and to stimulate plant immunity. Micromonospora strains isolated from surface sterilized nodules of alfalfa showed in vitro antifungal activity against several pathogenic fungi. Moreover, root inoculation of tomato plants with these Micromonospora strains effectively reduced leaf infection by the fungal pathogen Botrytis cinerea, despite spatial separation between both microorganisms. This induced systemic resistance, confirmed in different tomato cultivars, is long lasting. Gene expression analyses evidenced that Micromonospora stimulates the plant capacity to activate defense mechanisms upon pathogen attack. The defensive response of tomato plants inoculated with Micromonospora spp. differs from that of non-inoculated plants, showing a stronger induction of jasmonate-regulated defenses when the plant is challenged with a pathogen. The hypothesis of jasmonates playing a key role in this defense priming effect was confirmed using defense-impaired tomato mutants, since the JA-deficient line def1 was unable to display a long term induced resistance upon Micromonospora spp. inoculation. In conclusion, nodule isolated Micromonospora strains should be considered excellent candidates as biocontrol agents as they combine both direct antifungal activity against plant pathogens and the ability to prime plant immunity.

No MeSH data available.


Related in: MedlinePlus