An autophotographic determination of the active oxygen generation in potato tuber discs during hypersensitive response to fungal infection or elicitor

Abstract

During the hypersensitive reaction of potato tuber discs following inoculation with an incompatible race of Phytophthora infestans or treatment with the fungal wall elicitor (HWC-elicitor), a chemiluminescence (CL) was autophotographically detected on the tissues-surface by exposing X-ray film for several minutes to the fungal-inoculated or HWC-elicitor treated surface of tuber discs together with luminol. A densitometric analysis of CL on the autophotograms made it possible to show that the CL was dependent on concentrations of applied HWC-elicitor or luminol and that the presence of catalase or a scavenger of active oxygen, tiron, effectively diminished the CL. The HWC-elicitor stimulated CL was inhibited by an extracellular Ca 2+ chelator (EGTA), Ca 2+ channel blockers (verapamil, diltiazem and CoCl 2), a calmodulin inhibitor (W-7) and a protein kinase inhibitor (staurosporine). These results confirmed that a system of active oxygen generation in potato tuber discs was stimulated by infection with incompatible fungus or treatment with HWC-elicitor, and also suggested that Ca 2+, calumodulin and protein kinase may be involved in the stimulation process of the active oxygen generating system.