IDENTIFICATION AND CHARACTERIZATION OF GENES EXPRESSED DURING RICE-MAGNAPORTHE GRISEA INTERACTIONS

School of Agricultural Biotechnology, Seoul National University, Suwon 441-744, Korea

Expressed sequence tag (EST) analysis was conducted to identify rice genes involved in defense responses against infection by the blast fungus Magnaporthe grisea and fungal genes involved in infectious growth within the host in a compatible interaction. Two different cDNA libraries were constructed: a cDNA library from rice leaves (Oryza sativa cv. Hwacheong) infected with M. grisea strain KJ201 and a suppression subtractive cDNA library to enrich the fungal genes expressed in planta. Sequencing of 4,248 clones generated 2,315 non-redundant ESTs. Based on the similarity searches against genome drafts of M. grisea, Indica-type rice, and dbEST entries with BlastN algorithm, 708 and 1,542 ESTs could be identified to encode fungal and rice genes, respectively. Of the 708 fungal genes, 319 ESTs did not show significant homology to about 20,000 ESTs of M. grisea suggesting that these ESTs might be novel genes uniquely or preferentially expressed during infectious growth. Twenty most abundant ESTs showed different expression profiles when compared with the proportions in other libraries constructed from mycelia, conidia, or appressorial stages of M. grisea. Transcriptional profiling and high-throughput functional analysis of fungal genes expressed in planta is in progress.