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.