CATALASE-A FROM BOTRYTIS-CINEREA IS NOT EXPRESSED DURING INFECTION ONTOMATO LEAVES

Catalase mediates the enzymatic breakdown of hydrogen peroxide to wate r and molecular oxygen. During the infection of broad bean (Vicia faba ) by Botrytis cinerea the release of hydrogen peroxide by fungal oxida se activity was proposed to facilitate penetration by the pathogen. Ca talase 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 analys is of genomic DNA indicated the presence of a single copy gene, denote d as catA. The cDNA clone encoded a protein, CAT-A, of 480 amino acids showing 56-65% similarity to fungal catalases. Detailed analysis of s equence homologies between other fungal catalases enabled grouping of catalases according to their cellular location. CAT-A of B. cinerea re sembled most closely the peroxisomal catalases. Northern blot analysis showed induction of the gene by H2O2 in vitro. In planta, no catA exp ression could be detected by northern blot analysis, whereas a constit utively expressed beta-tubulin mRNA of B. cinerea was detectable and s ymptom 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 th e interaction. (C) 1997 Academic Press Limited.