Antioxidative defense activation in soybean cells

Suspension-cultured, photoheterotrophically grown, green soybean cells (Glycine max L.) were used to investigate alterations in the cellular contents of ascorbate and glutathione, as well as specific activities of antioxidative enzymes, elicited by salicylic acid (SA) and BTH [benzo(1,2,3)thiadiazole-7-carbothioic acid S-methylester]. Both antioxidants were positively regulated by 48-h incubations with SA and BTH, respectively, the latter induced a stronger increase in antioxidant levels compared to SA. The specific activities of glutathione reductase, monodehydroascorbate reductase and glutathione S-transferase increased strongly in soybean cells as a response to both SA and BTH. The enzyme activations observed were in the range of 2-8-fold. Catalase activity was also increased 2-fold by SA but decreased when cells were incubated with BTH. These results indicate an activation of the cellular antioxidative system at both the antioxidant and enzyme level. In addition, the effects of SA and BTH on phytotoxicity exerted by the peroxidizing herbicide oxyfluorfen were investigated. Both compounds protected soybean cells from herbicide-induced lipid peroxidation in a time- and concentration-dependent manner and strongly suppressed the herbicide-induced accumulation of protoporphyrin IX. SA as well as BTH antagonize the action of peroxidizing herbicides.