Large-scale identification of transcripts expressed in a symbiotic fungus (Termitomyces) during plant biomass degradation.

Fungus-growing termites have a symbiotic relationship with the basidiomycetes of the genus Termitomyces. This symbiotic system is able to degrade dead plant material efficiently. We conducted expressed sequence tag (EST) analysis of a symbiotic Termitomyces fungus degrading plant material in a field nest of the termite Macrotermes gilvus. A subtractive cDNA library was also investigated to facilitate the discovery of genes expressed specifically under the symbiotic conditions. A total of 2,613 ESTs were collected and resulted in 1,582 nonredundant tentative consensus sequences, of which approximately 59% showed significant similarity to known protein sequences. A number of homologous sequences to genes involved in plant cell wall degradation were identified and a majority of them encoded putative pectinolytic enzymes. Real-time quantitative reverse transcriptase polymerase chain reaction analyses confirmed significant upregulation of putative stress response genes under symbiotic conditions. The present ESTs database provides a valuable resource for molecular biological study of plant material degradation in the symbiosis between termites and fungi.