Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/11/2004
Publication Date: 12/11/2004
Citation: Goswami, R.S., Xu, J.-R., Kistler, H.C. 2004. Identification of genes expressed by Fusarium graminearum during infection of wheat [abstract]. 2nd International Symposium on Fusarium Head Blight Proceedings. p. 565.
Technical Abstract: Our initial studies have shown that the Fusarium graminearum species complex is comprised of strains belonging to at least nine biogeographically structured cryptic species that may differ significantly in their aggressiveness on wheat and mycotoxin production. To study this host-pathogen interaction at a genomic level and identify fungal genes expressed during initial infection (48 hours after inoculation), cDNA libraries were created by suppression subtractive hybridization. One such library was constructed using wheat heads inoculated with a highly aggressive strain (tester) or with water (driver). Twelve hundred and thirty six ESTs sequenced from this library could be assembled into 182 contigs and 630 singletons. Of these, 349 ESTs were determined to be of fungal origin according to their matches to the F. graminearum whole genome sequence. These sequences were compared with ESTs from libraries created using the same pathogen grown under various culture conditions and the whole genome sequences of Magnaporthe grisea and Neurospora crassa. Putative functions of genes corresponding to the fungal ESTs obtained from this library were predicted based on comparisons with sequences from publicly available databases. According to these predictions, predominantly mitochondrial ESTs were observed accounting for nearly 56% of the fungal ESTs. A significant number of ESTs with no known homologs in currently available databases were detected. These are believed to be new open reading frames specific to F. graminearum. Additionally, candidate sequences potentially involved in pathogenicity also were identified, e.g., those corresponding to genes coding for an ABC transporter, amino acid permease, polyketide synthase, histidine kinase, and the regulatory gene alcR. Some of these have been targeted for site-directed mutagenesis using gene replacement. Analysis of mutations in these sequences and the methods used for successful gene replacement in F. graminearum will be presented.