Response of the maize catalases and superoxide dismutases to cercosporin‐containing fungal extracts: the pattern of catalase response in scutella is stage specific

Abstract

Cercosporin, a photoactivated polyketide toxin produced by fungi of the genus Cercospora, reacts with molecular oxygen to produce oxygen radicals. Using both minus‐and plus‐cercosporin fungal extracts and purified cercosporin, we have analyzed antioxdant defense gene responses in maize scutella at two stages in development. The three maize catalases (CATH2O2: H2O2 oxidoreductase, EC 1.11.1.6) respond differentially to applied cercosporin, and this response varies with developmental stage. Total catalase activity, as well as individual isozyme proteins and their corresponding steady‐state levels of RNA changed in parallel in response to applied cercosporin. In contrast, both toal superoxide dismutase (SOD, O2:O2 oxidoreductase; EC 1.15.1.1) activity and individual isozyme protein levels remained constant in all treatments. Sod transcript accumulation, however, changed dramatically. Comparison of the response of these genes to minus‐ and plus‐cercosporin fungal extracts with their response to purified cercosporin demonstrated that other fungal compounds influence the expression of bothSod and Cat.