This thesis was performed within the research project “TrophinOak”, which addresses the
impact of multitrophic interactions on the pedunculate oak (Quercus robur) clone DF159. In
this frame, the present work focuses on the genetic and physiological mechanisms ruling the
interaction of the mycorrhiza helper bacterium (MHB) Streptomyces sp. AcH 505 with
microcuttings of DF159 either alone or in presence of the ectomycorrhizal fungus
Piloderma croceum or the fungal leaf pathogen oak powdery mildew
Microsphaera alphitoides. The work consists of 3 chapters.
Chapter 1 characterises the growth of AcH 505 and P. croceum in a soil-based culture system
used within the TrophinOak project. Besides the establishment and evaluation of
quantification methods of these microorganisms by quantitative real-time PCR, the impact of
the soil microbial community and the oak on the bacterium-fungus interaction was
investigated, and AcH 505 and P. croceum were visualized by scanning electron microscopy.
It was observed that the presence of the soil microorganisms and the oak both affect the
bacterium-fungus interaction, and that P. croceum enhances the growth of AcH 505.
Chapter 2 presents a study with the oak, AcH 505 and the EM fungus P. croceum, enabling to
disentangle the direct effect of the MHB on the oak from the indirect one via the EM
symbiosis. The used approach was transcriptomic based on RNA sequencing. It was shown
that i) differential gene expression occurred between root and the distant leaf tissues (local vs.
systemic effects), different developmental stages and treatments, suggesting that oak
specifically coordinates its gene expression patterns, and ii) that genes related to plant growth,
defence and DNA modification were dominant among the differential expressed genes,
suggesting that these processes play essential roles in both symbiotic interactions investigated.
Chapter 3 represents a second transcriptome study, addressing how AcH 505 suppresses
powdery mildew infection in oak by analysing RNA Sequencing data from singly- and coinoculated
oaks. This study combined the systemic impact of the root associated bacterium
with local effects of the leaf pathogen, thereby linking belowground and aboveground
interactions. Systemic defence response is induced by the bacterium and further enhanced
upon pathogen challenge, suggesting that on the leaf level, some bacterial effectors are
recognized as harmful for the plant.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:12429 |
| Date | 28 August 2015 |
| Creators | Kurth, Florence |
| Contributors | Tarkka, Mika, Buscot, Francois, Nehls, Uwe, Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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