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Gene Discovery and Gene Expression in the Rice Blast Fungus, Magnaporthe grisea: Analysis of Expressed Sequence Tags

December 2004 , Volume 17 , Number  12
Pages  1,337 - 1,347

Daniel J. Ebbole , 1 Yuan Jin , 1 Michael Thon , 1 Huaqin Pan , 2 Eric Bhattarai , 1 Terry Thomas , 3 and Ralph Dean 2

1Program for the Biology of Filamentous Fungi, Department of Plant Pathology & Microbiology, Texas A&M University, College Station, U.S.A.; 2Fungal Genomics Laboratory, Center for Integrated Fungal Research, North Carolina State University, Raleigh, U.S.A.; 3Department of Biology, Texas A&M University, College Station, U.S.A.

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Accepted 26 July 2004.

Over 28,000 expressed sequence tags (ESTs) were produced from cDNA libraries representing a variety of growth conditions and cell types. Several Magnaporthe grisea strains were used to produce the libraries, including a nonpathogenic strain bearing a mutation in the PMK1 mitogen-activated protein kinase. Approximately 23,000 of the ESTs could be clustered into 3,050 contigs, leaving 5,127 singleton sequences. The estimate of 8,177 unique sequences indicates that over half of the genes of the fungus are represented in the ESTs. Analysis of EST frequency reveals growth and cell type-specific patterns of gene expression. This analysis establishes criteria for identification of fungal genes involved in pathogenesis. A large fraction of the genes represented by ESTs have no known function or described homologs. Manual annotation of the most abundant cDNAs with no known homologs allowed us to identify a family of metallothionein proteins present in M. grisea, Neurospora crassa, and Fusarium graminearum. In addition, multiply represented ESTs permitted the identification of alternatively spliced mRNA species. Alternative splicing was rare, and in most cases, the alternate mRNA forms were unspliced, although alternative 5′ splice sites were also observed.

Additional keyword: plant pathogen.

© 2004 The American Phytopathological Society