Abstract
BackgroundGrosmannia clavigera is a bark beetle-vectored fungal pathogen of pines that causes wood discoloration and may kill trees by disrupting nutrient and water transport. Trees respond to attacks from beetles and associated fungi by releasing terpenoid and phenolic defense compounds. It is unclear which genes are important for G. clavigera's ability to overcome antifungal pine terpenoids and phenolics.ResultsWe constructed seven cDNA libraries from eight G. clavigera isolates grown under various culture conditions, and Sanger sequenced the 5' and 3' ends of 25,000 cDNA clones, resulting in 44,288 high quality ESTs. The assembled dataset of unique transcripts (unigenes) consists of 6,265 contigs and 2,459 singletons that mapped to 6,467 locations on the G. clavigera reference genome, representing ~70% of the predicted G. clavigera genes. Although only 54% of the unigenes matched characterized proteins at the NCBI database, this dataset extensively covers major metabolic pathways, cellular processes, and genes necessary for response to environmental stimuli and genetic information processing. Furthermore, we identified genes expressed in spores prior to germination, and genes involved in response to treatment with lodgepole pine phloem extract (LPPE).ConclusionsWe provide a comprehensively annotated EST dataset for G. clavigera that represents a rich resource for gene characterization in this and other ophiostomatoid fungi. Genes expressed in response to LPPE treatment are indicative of fungal oxidative stress response. We identified two clusters of potentially functionally related genes responsive to LPPE treatment. Furthermore, we report a simple method for identifying contig misassemblies in de novo assembled EST collections caused by gene overlap on the genome.
Highlights
Grosmannia clavigera is a bark beetle-vectored fungal pathogen of pines that causes wood discoloration and may kill trees by disrupting nutrient and water transport
Like many bark beetle associated fungi, G. clavigera produces slimy spores that stick to the exoskeleton of the insects, but the fungus is present in the beetle mycangia
We analyzed a small set of expressed sequence tags (ESTs) from G. clavigera and found putative gene candidates that may be involved in terpenoid detoxification [13]
Summary
Grosmannia clavigera is a bark beetle-vectored fungal pathogen of pines that causes wood discoloration and may kill trees by disrupting nutrient and water transport. Trees respond to attacks from beetles and associated fungi by releasing terpenoid and phenolic defense compounds. The ophiostomatoid fungus Grosmannia clavigera (Robinson-Jeffrey and Davidson) is a fungal pathogen that discolours wood, and kills pine host trees by disrupting the flow of nutrients and water in phloem and sapwood [1,2]. G. clavigera is vectored between hosts by the mountain pine beetle (MPB, Dendroctonus ponderosae) This pathogen can kill lodgepole pine (Pinus contorta) when manually inoculated under the bark at a high enough concentration [3,4]. Whether G. clavigera encodes and expresses genes necessary for detoxification of phenolic compounds has not been determined
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