ALTERNATIVE SPLICING AND EDITING OF PEROXIDASE GENE DETERMINE THE SPECIFIC RESISTANCE TO POWDERY MILDEW PATHOGEN AND THE SPECIFIC RESPONSE TO WOUNDING IN Triticum aestivum L.

Eastern Cereal and Oilseed Research Center, 960 Carling Avenue, Ottawa, Ontario K1A 0C6, Canada

Alternative splicing and editing of peroxidase gene determine the specific resistance to powdery mildew pathogen and the specific response to wounding in Triticum aestivum L. Davis W. Cheng, Ken Armstrong and George Fedak Eastern Cereal and Oilseed Research Center Agriculture and Agri-Food Canada 960 Carling Avenue, Ottawa, Ontario K1A 0C6, Canada We cloned a set of peroxidase ( pxc ) alleles from two wheat ( Triticum aestivum L. ) cultivars differed in resistance to powdery mildew pathogen ( Erysiphe graminis f. sp.tritici ). The molecular structures of the pxc alleles are highly diverged in the promoter region, but highly conserved in the ORF region which contains a signal peptide sequence 5' end region of coding domain, 3 exons and 2 introns in almost the same position. Upon inoculation of one-month-old plants with a spore suspension of the powdery mildew pathogen and physical treatment of the leaves by wounding, the temporal relationship of the splicing/editing of the pxc gene and the resistance to the pathogen was examined in pxc transcripts by sequence analysis of cDNAs derived from total leaves. It has been shown that (1) wounding induced the specific expression of the pxc gene only in the leaves of Ac Dexter; (2) powdery mildew pathogen induced the specific expression of the pxc gene in the leaves of both cultivars; (3) only the larger size transcripts induced by the pathogen in resistant cultivar showed correct splicing and editing and produced a functional translation product. These results indicate that the signals from pathogen and wounding are different in the activation of pxc gene expression; a lot of molecular "garbage" was produced in vivo with the physical and biological stimuli; only the correctly processed post-transcripts of the peroxidase genes were involved in resistance to powdery mildew pathogen in wheat.