Abstract

Fungal phytopathogens continue to cause major economic impact, either directly, through crop losses, or due to the costs of fungicide application. Attempts to understand these organisms are hampered by a lack of fungal genome sequence data. A need exists, however, to develop specific bioinformatics tools to collate and analyse the sequence data that currently is available. A web-accessible gene discovery database (http://cogeme.ex.ac.uk/biosynthesis.html) was developed as a demonstration tool for the analysis of metabolic and signal transduction pathways in pathogenic fungi using incomplete gene inventories. Using Bayesian probability to analyse the currently available gene information from pathogenic fungi, we provide evidence that the obligate pathogen Blumeria graminis possesses all amino acid biosynthetic pathways found in free-living fungi, such as Saccharomyces cerevisiae. Phylogenetic analysis was also used to deduce a gene history of succinate-semialdehyde dehydrogenase, an enzyme in the glutamate and lysine biosynthesis pathways. The database provides a tool and methodology to researchers to direct experimentation towards predicting pathway conservation in pathogenic microorganisms.

Highlights

  • Fungal pathogens are responsible for serious diseases of humans and plants and are of considerable economic importance (Baker et al, 1997)

  • The pace of progress of fungal genome sequencing to date has been slow compared to other eukaryotes (Yoder and Turgeon, 2001; Soanes et al, 2002), with the first draft genome sequence of only one phytopathogenic fungus, Magnaponrthe grisea

  • Notwithstanding this limitation, the probability values provide information with the potential to provide early indications of the absence or presence of a particular amino acid pathway in an organism of interest, e.g. the data suggested the absence of a histidine biosynthesis pathway in G. zeae

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Summary

Introduction

Fungal pathogens are responsible for serious diseases of humans and plants and are of considerable economic importance (Baker et al, 1997). The complete genomes of only three fungi are available in the public domain: Saccharomyces cerevisiae (Goffeau et al, 1996); Schizosaccharomyces pombe (Wood et al, 2002) and Neurospora crassa (http://wwwgenome.wi.mit.edu/annotation/fungi/neurospora/), all of which are non-pathogenic species. The first draft of the genome sequence of a plant pathogenic fungus Magnaporthe grisea has very recently become available Wi.mit.edu/annotation/fungi/magnaporthe/), along with the first draft of the sequence of a human pathogen, Aspergillus fumigatus In the absence of a large number of completed phytopathogenic fungal genomes, single-pass, partial sequencing of either 3 or 5 ends of complementary DNA (cDNA) clones to generate a set of ESTs, offers a low-cost strategy to identify substantial gene inventories. A large number of phytopathogenic fungal ESTs have been deposited with annotation in a fungal EST database generated by the Consortium for the Genomics of Microbial Eukaryotes (COGEME: http://cogeme.ex.ac.uk)

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