CUTINASE-A OF BOTRYTIS-CINEREA IS EXPRESSED, BUT NOT ESSENTIAL, DURING PENETRATION OF GERBERA AND TOMATO

The plant pathogen Botrytis cinerea can infect undamaged plant tissue directly by penetration of the cuticle. This penetration has been sugg ested to be enzyme-mediated, and an important role for cutinase in the infection process has been proposed, In this study the expression of the cutinase encoding gene cutA of B. cinerea was analyzed using a cut A promoter-GUS reporter gene fusion. Transformants containing the fusi on construct were examined for GUS expression on gerbera flowers and t omato fruits. High GUS activity was detected from the onset of conidia l germination and during penetration into epidermal cells, indicating that cutA is expressed during the early stages of infection. To determ ine the biological relevance of cutinase A for successful penetration, cutinase A-deficient mutants were constructed by gene disruption. Pat hogenicity of two transformants lacking a functional cutA gene was stu died an gerbera flowers and tomato fruits. Their ability to penetrate and cause symptoms was unaltered compared to the wild-type strain. The se results exclude an important role for cutinase A during direct pene tration of host tissue by B. cinerea.