Identification of mature appressorium-enriched transcripts in Magnaporthe grisea, the rice blast fungus, using suppression subtractive hybridization.

We have constructed a fungal subtractive suppressive library enriched in genes expressed during appressorium maturation in Magnaporthe grisea. Sequencing of 250 clones from the subtracted appressorium cDNA library revealed 142 unique genes, represented by 155 non-redundant ESTs (expressed sequence tags). Of these ESTs, 72 have not been previously isolated in M. grisea. RT-PCR analysis of 105 of the genes discovered found transcripts corresponding to 71 of the ESTs only in mature appressoria while transcripts corresponding to a further 34 of the isolated ESTs were expressed both in appressoria and conidia/mycelia. Genes specifically expressed in appressorium identified by SSH included a number that have been previously implicated in appressorium formation or function including GAS1, GAS3, and PTH11.