Résumé
Wall-associated protein kinases (WAKs) are a new group of receptor-like kinases recently identified in Arabidopsis and in rice. A gene responsible for the quantitative resistance to Fusarium oxysporum in Arabidopsis, RFO1, encodes a WAK-like protein (WAKL22) (Diener and Ausubel, 2005). This finding suggests an important role for some WAKs in disease resistance. The first WAK in rice was recently identified as OsWAK1. The induction and overexpression of this gene in rice led to enhanced resistance to rice blast (Li et al., 2008). Furthermore, WAKs also seem to interact with a wide range of proteins involved in cell-wall composition, phosphorylation or transcription processes (Li et al., 2008, Rohila et al., 2006, Yang et al., 2003). Altogether, the evidences suggest that WAKs are novel receptor-like kinases playing an important role in plant disease resistance. Microarray data reveal differential expression of some WAKs in rice leaves infected with Magnaporthe oryzae (Vergne et al., 2007). This set of WAKs was analysed by real time PCR in a time course experiment and confirmed the microarray results. This analysis also revealed differential expression for some WAKs very early after infection (4, 6 or 8 hours post inoculation), suggesting an early role in pathogen recognition. This early expression may be due to the recognition of common motifs of the fungal pathogens like chitin. Rice was sprayed with chitin and WAK expression was quantified at different time point after treatment. The results show that some WAKs are highly induced very early after chitin treatment (since 30 minutes and until 24 hours post treatment). Therefore some WAKs could play a role in basal resistance. To confirm a role of these WAKs in rice blast resistance, Knock-Out and transgenic rice lines with constitutive expression of a subset of WAKs were produced. Preliminary data supporting the role of this gene family in disease resistance in rice will be presented.