The genome of the emerging barley pathogen Ramularia collo-cygni.

BACKGROUND: Ramularia collo-cygni is a newly important, foliar fungal pathogen of barley that causes the disease Ramularia leaf spot. The fungus exhibits a prolonged endophytic growth stage before switching life habit to become an aggressive, necrotrophic pathogen that causes significant losses to green leaf area and hence grain yield and quality. RESULTS: The R. collo-cygni genome was sequenced using a combination of Illumina and Roche 454 technologies. The draft assembly of 30.3 Mb contained 11,617 predicted gene models. Our phylogenomic analysis confirmed the classification of this ascomycete fungus within the family Mycosphaerellaceae, order Capnodiales of the class Dothideomycetes. A predicted secretome comprising 1053 proteins included redox-related enzymes and carbohydrate-modifying enzymes and proteases. The relative paucity of plant cell wall degrading enzyme genes may be associated with the stealth pathogenesis characteristic of plant pathogens from the Mycosphaerellaceae. A large number of genes associated with secondary metabolite production, including homologs of toxin biosynthesis genes found in other Dothideomycete plant pathogens, were identified. CONCLUSIONS: The genome sequence of R. collo-cygni provides a framework for understanding the genetic basis of pathogenesis in this important emerging pathogen. The reduced complement of carbohydrate-degrading enzyme genes is likely to reflect a strategy to avoid detection by host defences during its prolonged asymptomatic growth. Of particular interest will be the analysis of R. collo-cygni gene expression during interactions with the host barley, to understand what triggers this fungus to switch from being a benign endophyte to an aggressive necrotroph.

Inducibility studies with the arbuscular mycorrhizal fungus Glomus mosseae 3-phosphoglycerate kinase (PGK) gene promoter.

Arbuscular mycorrhizal (AM) fungi are a multifaceted group of mutualistic symbionts that are common to terrestrial ecosystems. The role of AM fungi within processes related to carbon (C) dynamics of the plant-root-soil system are of global significance. An understanding of the C metabolism of AM fungi within the symbiotic and asymbiotic stages of their lifecycle is a necessary pre-requisite to understanding the mechanisms of C movement. This investigation studies the regulation of the Glomus mosseae (Gm) 3-phosphoglycerate kinase ( PGK) gene promoter by different C sources. The suitability of studying the GmPGK promoter (P(GmPGK)) within Saccharomyces cerevisiae was confirmed by complementation of a S. cerevisiae pgk (-) mutant with an expression vector carrying the P(GmPGK) driving the expression of the S. cerevisiae PGK gene. The inducibility of the P(GmPGK) to different C sources was studied by creating a P(GmPGK)-luciferase fusion, which was introduced into a S. cerevisiae expression vector and used to transform S. cerevisiae. The P(GmPGK)-luciferase fusion was tested for expression within S. cerevisiae by RT-PCR analysis and was shown to be expressing the luciferase gene. C upshift studies were completed to evaluate the inducibility of this promoter by different C sources. The sources raffinose, glycerol and glucose significantly induced the P(GmPGK), whereas the sources galactose, succinate and sucrose had the lowest transcriptional responses. Semi-quantitative RT-PCR was used to establish gene expression patterns of GmPGK during spore germination; and up-regulation of the GmPGK gene was observed.