Repeated leaf wounding alters the colonization of Medicago truncatula roots by beneficial and pathogenic microorganisms

ABSTRACT In nature, plants are subject to various stresses that are often accompanied by wounding of the aboveground tissues. As wounding affects plants locally and systemically, we investigated the impact of leaf wounding on interactions of Medicago truncatula with root‐colonizing microorganisms, s...

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Published in:Plant, cell and environment cell and environment, 2012-07, Vol.35 (7), p.1344-1357
Main Authors: LANDGRAF, RAMONA, SCHAARSCHMIDT, SARA, HAUSE, BETTINA
Format: Article
Language:English
Subjects:
Aphanomyces - pathogenicity
Aphanomyces euteiches
arbuscular mycorrhiza
Biological and medical sciences
Cyclopentanes - pharmacology
Fundamental and applied biological sciences. Psychology
Fungal plant pathogens
Gene Expression Regulation, Plant
Glomus intraradices
Intramolecular Oxidoreductases - genetics
Intramolecular Oxidoreductases - metabolism
jasmonic acid
Medicago truncatula (barrel medic)
Medicago truncatula - microbiology
Mycorrhizae - physiology
nitrogen-fixing rhizobia
Oxylipins - pharmacology
Parasitism and symbiosis
Phytopathology. Animal pests. Plant and forest protection
Plant Leaves - physiology
Plant physiology and development
Plant Proteins - genetics
Plant Proteins - metabolism
Plant Roots - microbiology
plant wounding
Sinorhizobium meliloti - physiology
Symbiosis
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Summary:ABSTRACT In nature, plants are subject to various stresses that are often accompanied by wounding of the aboveground tissues. As wounding affects plants locally and systemically, we investigated the impact of leaf wounding on interactions of Medicago truncatula with root‐colonizing microorganisms, such as the arbuscular mycorrhizal (AM) fungus Glomus intraradices, the pathogenic oomycete Aphanomyces euteiches and the nitrogen‐fixing bacterium Sinorhizobium meliloti. To obtain a long‐lasting wound response, repeated wounding was performed and resulted in locally and systemically increased jasmonic acid (JA) levels accompanied by the expression of jasmonate‐induced genes, among them the genes encoding allene oxide cyclase 1 (MtAOC1) and a putative cell wall‐bound invertase (cwINV). After repeated wounding, colonization with the AM fungus was increased, suggesting a role of jasmonates as positive regulators of mycorrhization, whereas the interaction with the rhizobacterium was not affected. In contrast, wounded plants appeared to be less susceptible to pathogens which might be caused by JA‐induced defence mechanisms. The effects of wounding on mycorrhization and pathogen infection could be partially mimicked by foliar application of JA. In addition to JA itself, the positive effect on mycorrhization might be mediated by systemically induced cwINV, which was previously shown to exhibit a regulatory function on interaction with AM fungi. Plants are subjected in nature to various stresses that are often accompanied with mechanical wounding. Because wounding can affect plants systemically, we analyzed the effect of leaf wounding on root‐colonizing microbes. For that purpose, Medicago truncatula plants were inoculated either with symbiotic or pathogenic root‐colonizing microorganisms, and were then slightly but repeatedly wounded on leaves. Repeatedly performed leaf wounding led to a long‐lasting wound response and a systemic activation of jasmonic acid biosynthesis. Interestingly, the interactions of M. truncatula with the tested microbes were differentially affected by the wound treatment. The role of jasmonates and/or systemically induced invertases in the effect of leaf wounding on biotic interactions established in the root is discussed.
ISSN:0140-7791
1365-3040
DOI:10.1111/j.1365-3040.2012.02495.x