Interactions Illuminated by Genome Sequencing and EST
Analysis of the Wheat Pathogen Stagonospora nodorumW
James K. Hane,a,1 Rohan G.T. Lowe,a,1
Peter S. Solomon,aKar-Chun Tan,a
Conrad L. Schoch,b Joseph W. Spatafora,b
PedroW. Crous,c Chinappa Kodira,d
Bruce W. Birren,d James E. Galagan,d
Stefano F.F. Torriani,e Bruce A. McDonald,e
and Richard P. Olivera,2
Australian Centre for Necrotrophic Fungal Pathogens,
Murdoch University, WA 6150, Australia.
Stagonospora nodorum is
a major necrotrophic fungal pathogen of wheat (Triticum
aestivum) and a member of the
Dothideomycetes, a large fungal taxon that includes
many important plant pathogens affecting all major
crop plant families.
Here,we report the acquisitionandinitialanalysis ofa
draftgenomesequencefor this fungus.The assemblycomprises
bp of nuclear DNA contained in 107 scaffolds. The
circular mitochondrial genome comprises 49,761 bp
encoding 46 genes,
including four that are intron encoded. The nuclear
genome assembly contains 26 classes of repetitive
DNA, comprising 4.5%of
the genome. Some of the repeats showevidence of repeat-induced
pointmutations consistentwith a frequent sexual cycle.
and gene predictionmodels support aminimum of 10,762
nuclear genes. Extensive orthology was found between
synthase family in S. nodorum and Cochliobolus
heterostrophus, suggesting an ancient origin
and conserved functions for these
genes. A striking feature of the gene catalog was
the large number of genes predicted to encode secreted
proteins; the majority
has no meaningful similarity to any other known genes.
It is likely that genes for host-specific toxins,
in addition to ToxA, will be
found among this group. ESTs obtained from axenicmyceliumgrown
on oleate (chosen tomimic early infection) and late-stage
lesions sporulating on wheat leaves were obtained.
Statistical analysis shows that transcripts encoding
proteins involved in
protein synthesis and in the production of extracellular
proteases, cellulases, and xylanases predominate in
the infection library.
This suggests that the fungus is dependant on the
degradation of wheat macromolecular constituents to
provide the carbon
skeletons and energy for the synthesis of proteins
and other components destined for the developing pycnidiospores.
nodorum, Triticum aestivum, Dothideomycetes,Cochliobolus