Submitted to: International Congress on Molecular Plant-Microbe Interactions
Publication Type: Abstract Only
Publication Acceptance Date: 7/23/2001
Publication Date: N/A
Technical Abstract: The photoactivated phytotoxin, cercosporin, is produced by numerous species of Cercosporoid fungi and has been shown to be produced in culture in a light-dependant manner. The present work reveals that the sugarbeet leaf spot pathogen Cercospora beticola grown in liquid media produces esterase activity also in a light-dependant fashion. In cultures grown in the dark and subsequently shifted to constant illumination, greater esterase activity was observed in cultures exposed for 48 hr of light than in parallel cultures maintained in constant darkness. Time course analysis indicated a detectable increase of esterase activity in culture supernatants that began at 4 hr post- illumination and plateaued at 72 hr post-illumination. Data from parallel analysis of cultured mycelia and culture supernatants suggested that secretion of esterase activity is highly light-regulated, whereas synthesis of esterase activity within the fungus is less light- dependant. Native polyacrylamide gel electrophoresis (PAGE) of culture supernatants revealed two isozyme classes contributing to the total esterase activity. In denaturing PAGE, the major secreted esterase isozyme migrated at approximately 80,000 MW. The potential role of secreted esterase as a virulence factor in the infection of sugarbeet by C. beticola is discussed.