CLONING, CHARACTERIZATION, AND TARGETED DISRUPTION OF CPCAT1, CODING FOR AN IN PLANTA SECRETED CATALASE OF CLAVICEPS-PURPUREA

Claviceps purpurea has been shown to secrete catalases in axenic and p arasitic culture. In order to determine the importance of these enzyme s in the host-parasite interaction, especially their role in overcomin g oxidative stress imposed on the pathogen by the plant's defense syst em, the catR gene from A. niger was used to isolate a putative catalas e gene from a genomic library of C. purpurea, cpcat1 consists of an op en reading frame of 2,148 bp that is interrupted by five introns, Its derived gene product shows significant homology to fungal catalases an d contains a putative signal peptide of 19 amino acids and three putat ive N-glycosylation sites, which indicates that CPCAT1 is a secreted c atalase, Disruption of the gene by a gene replacement approach resulte d in the loss of two catalase isoforms, CATC and CATD, strongly sugges ting that they are both encoded by cpcat1, CATD is the major secreted catalase of C. purpurea and is furthermore the only catalase present i n the honeydew of infected rye ears. Deletion mutants of cpcat1 were i noculated on rye plants and showed no significant reduction in virulen ce. Ovarian tissue and honeydew of plants inoculated with the mutants lacked CATD, confirming that this catalase is not essential for coloni zation of the host tissue by C. purpurea.