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BMC Genomics. 2018 May 22;19(1):381. doi: 10.1186/s12864-018-4750-6.

Signatures of host specialization and a recent transposable element burst in the dynamic one-speed genome of the fungal barley powdery mildew pathogen.

Author information

1
Institute for Biology I, Unit of Plant Molecular Cell Biology, RWTH Aachen University, Worringerweg 1, 52056, Aachen, Germany.
2
Max Planck Institute for Plant Breeding Research, Department of Plant-Microbe Interactions, Carl-von-Linné-Weg 10, 50829, Cologne, Germany.
3
Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg, Denmark.
4
Imperial College, Department of Life Sciences, Sir Alexander Fleming Building, London, SW7 2AZ, UK.
5
Max Planck Institute for Plant Breeding Research, Department of Plant-Microbe Interactions, Carl-von-Linné-Weg 10, 50829, Cologne, Germany. maekawa@mpipz.mpg.de.
6
Max Planck Institute for Plant Breeding Research, Department of Plant-Microbe Interactions, Carl-von-Linné-Weg 10, 50829, Cologne, Germany. schlef@mpipz.mpg.de.
7
Institute for Biology I, Unit of Plant Molecular Cell Biology, RWTH Aachen University, Worringerweg 1, 52056, Aachen, Germany. panstruga@bio1.rwth-aachen.de.

Abstract

BACKGROUND:

Powdery mildews are biotrophic pathogenic fungi infecting a number of economically important plants. The grass powdery mildew, Blumeria graminis, has become a model organism to study host specialization of obligate biotrophic fungal pathogens. We resolved the large-scale genomic architecture of B. graminis forma specialis hordei (Bgh) to explore the potential influence of its genome organization on the co-evolutionary process with its host plant, barley (Hordeum vulgare).

RESULTS:

The near-chromosome level assemblies of the Bgh reference isolate DH14 and one of the most diversified isolates, RACE1, enabled a comparative analysis of these haploid genomes, which are highly enriched with transposable elements (TEs). We found largely retained genome synteny and gene repertoires, yet detected copy number variation (CNV) of secretion signal peptide-containing protein-coding genes (SPs) and locally disrupted synteny blocks. Genes coding for sequence-related SPs are often locally clustered, but neither the SPs nor the TEs reside preferentially in genomic regions with unique features. Extended comparative analysis with different host-specific B. graminis formae speciales revealed the existence of a core suite of SPs, but also isolate-specific SP sets as well as congruence of SP CNV and phylogenetic relationship. We further detected evidence for a recent, lineage-specific expansion of TEs in the Bgh genome.

CONCLUSIONS:

The characteristics of the Bgh genome (largely retained synteny, CNV of SP genes, recently proliferated TEs and a lack of significant compartmentalization) are consistent with a "one-speed" genome that differs in its architecture and (co-)evolutionary pattern from the "two-speed" genomes reported for several other filamentous phytopathogens.

KEYWORDS:

Co-evolution; Copy number variation; Effectorome; Evolutionary genomics; Fungal genomics; Host specialization; Synteny; Transposable elements

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