Study of lipoxygenase and phenylalanine ammonia-lyase gene expression and activity of related enzymes in rice under stress of Rhizoctonia solani, the causal agent of sheath blight disease, antagonistic and inducer bacteria in combination with potassium silicate

Induced resistance is one of the ways by which plants cope with the biotic stress. Phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) as inducible defense enzymes, are synthesized by plant in response to biotic stress. This research was carried out with the aim of investigating the effect of Pseudomonas sp. isolates (antagonistic and inducer bacteria) and potassium silicate treatment on expression changes and production of enzymes at 0, 6, 12, 24, 48 and 72 hours after rice seedling contamination of Fajr cultivar to R. solani, the causal agent of rice sheath blight disease. Analysis of gene expression showed that the maximum expression was observed in 72 hours after plant inoculation, and the combination of antagonistic bacteria and potassium silicate as an inducer had the highest expression during the first 6 hours of infection. Analysis of enzyme content showed that the use of treatment compounds in the initial time interval of zero to 6 hours were caused a significant increase in protein content, which was more than the phenylalanine ammonia-lyase in the combination of the antagonistic bacteria and the potassium silicate as an inducing agent for the lipoxygenase enzyme. In general, by attacking the pathogens, the plant increases the amount of these enzymes due to the important role of these genes in defense against the pathogen. Increasing the expression level of these genes directly increases the activity of the enzymes which indicate direct role of these gens in plant defense system, that, it is possible to increase their expression by applying potassium silicate and antagonistic and inducer bacteria on the plant.