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Cloning, Characterization, and Targeted Disruption of cpcat1, Coding for an in Planta Secreted Catalase of Claviceps purpurea

August 1998 , Volume 11 , Number  8
Pages  772 - 783

Victoriano Garre , Ulrike Müller , and Paul Tudzynski

Institut für Botanik, Westfälische Wilhelms-Universität, Schlossgarten 3, D-48149 Münster, Germany

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Accepted 27 April 1998.

Claviceps purpurea has been shown to secrete catalases in axenic and parasitic culture. In order to determine the importance of these enzymes in the host-parasite interaction, especially their role in overcoming oxidative stress imposed on the pathogen by the plant's defense system, the catR gene from A. niger was used to isolate a putative catalase gene from a genomic library of C. purpurea. cpcat1 consists of an open reading frame of 2,148 bp that is interrupted by five introns. Its derived gene product shows significant homology to fungal catalases and contains a putative signal peptide of 19 amino acids and three putative N-glycosylation sites, which indicates that CPCAT1 is a secreted catalase. Disruption of the gene by a gene replacement approach resulted in the loss of two catalase isoforms, CATC and CATD, strongly suggesting that they are both encoded by cpcat1. CATD is the major secreted catalase of C. purpurea and is furthermore the only catalase present in the honeydew of infected rye ears. Deletion mutants of cpcat1 were inoculated on rye plants and showed no significant reduction in virulence. Ovarian tissue and honeydew of plants inoculated with the mutants lacked CATD, confirming that this catalase is not essential for colonization of the host tissue by C. purpurea.

Additional keywords: active oxygen species.

© 1998 The American Phytopathological Society