Catalase A from Botrytis cinerea is not expressed during infection on tomato leaves

Catalase mediates the enzymatic breakdown of hydrogen peroxide to water and molecular oxygen. During the infection of broad bean (Vicia faba) by Botrytis cinerea the release of hydrogen peroxide by fungal oxidase activity was proposed to facilitate penetration by the pathogen. Catalase activity might play a role in protecting the fungus against the damaging effects of hydrogen peroxide. A cDNA clone encoding catalase was isolated from a library of Botrytis cinerea. Southern blot analysis of genomic DNA indicated the presence of a single copy gene, denoted as catA. The cDNA clone encoded a protein, CAT-A, of 480 amino acids showing 56-65% similarity to fungal catalases. Detailed analysis of sequence homologies between other fungal catalases enabled grouping of catalases according to their cellular location. CAT-A of B. cinerea resembled most closely the peroxisomal catalases. Northern blot analysis showed induction of the gene by H2O2 in vitro. In planta, no catA expression could be detected by northern blot analysis, whereas a constitutively expressed beta-tubulin mRNA of B. cinerea was detectable and symptom development on the inoculated leaves was very clear. However, a catalase gene carl of tomato appeared to be induced from the time of fungal penetration onwards, suggesting that H2O2 is produced during the interaction. (C) 1997 Academic Press Limited.