Early and specific gene expression triggered by rice resistance gene Pi33 in response to infection by ACE1 avirulent blast fungus

Our view of genes involved in rice disease resistance is far from complete. Here we used a gene-for-gene relationship corresponding to the interaction between atypical avirulence gene ACE1 from Magnaporthe grisea and rice resistance gene Pi33 to better characterize early rice defence responses induced during such interaction. Rice genes differentially expressed during early stages of Pi33/ACE1 interaction were identified using DNA chip-based differential hybridization and QRT-PCR survey of the expression of known and putative regulators of disease resistance. One hundred genes were identified as induced or repressed during rice defence response, 80% of which are novel, including resistance gene analogues. Pi33/ACE1 interaction also triggered the up-regulation of classical PR defence genes and a massive down-regulation of chlorophyll a/b binding genes. Most of these differentially expressed genes were induced or repressed earlier in Pi33/ACE1 interaction than in the gene-for-gene interaction involving Nipponbare resistant cultivar. Besides demonstrating that an ACE1/Pi33 interaction induced classical and specific expression patterns, this work provides a list of new genes likely to be involved in rice disease resistance.