Silvia D. Schrey,2 and
Mika T. Tarkka1,5
1UFZ–Helmholtz Centre for Environmental Research, Dept. Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle/Saale, Germany; 2Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Auf der Morgenstelle 1, Tübingen, Germany, 3Institute of Computer Science, Martin-Luther University, Von-Seckendorff-Platz 1, 06120, Halle/Saale, Germany; 4UFZ–Helmholtz Centre for Environmental Research, Dept. Community Ecology; 5German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany
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Accepted 22 April 2014.
Rhizobacteria are known to induce defense responses in plants without causing disease symptoms, resulting in increased resistance to plant pathogens. This study investigated how Streptomyces sp. strain AcH 505 suppressed oak powdery mildew infection in pedunculate oak, by analyzing RNA-Seq data from singly- and co-inoculated oaks. We found that this Streptomyces strain elicited a systemic defense response in oak that was, in part, enhanced upon pathogen challenge. In addition to induction of the jasmonic acid/ethylene–dependent pathway, the RNA-Seq data suggests the participation of the salicylic acid–dependent pathway. Transcripts related to tryptophan, phenylalanine, and phenylpropanoid biosynthesis were enriched and phenylalanine ammonia lyase activity increased, indicating that priming by Streptomyces spp. in pedunculate oak shares some determinants with the Pseudomonas-Arabidopsis system. Photosynthesis-related transcripts were depleted in response to powdery mildew infection, but AcH 505 alleviated this inhibition, which suggested there is a fitness benefit for primed plants upon pathogen challenge. This study offers novel insights into the mechanisms of priming by actinobacteria and highlights their capacity to activate plant defense responses in the absence of pathogen challenge.
© 2014 The American Phytopathological Society