Polygalacturonase is a pathogenicity factor in the Claviceps purpurealrye interaction

Claviceps purpurea is a biotrophic, organ-specific pathogen of grasses and cereals, attacking exclusively young ovaries. We have previously shown that its mainly intercellular growth is accompanied by degradation of pectin, and that two endopolygalacturonase genes (cppg1/cppg2) are expressed throughout all stages of infection. We report here on a functional analysis of these genes using a gene-replacement approach. Mutants lacking both polygalacturonase genes are not affected in their vegetative properties, but they are nearly nonpathogenic on rye. Complementation of the mutants with wild-type copies of cppg1 and cppg2 fully restored pathogenicity, proving that the endopolygalacturonases encoded by cppg1 and eppg2 represent pathogenicity factors in the interaction system C. purpurea/Secale cereale, the first unequivocally identified so far in this system. (C) 2002 Elsevier Science (USA). All rights reserved.