Modifications of antioxidant activity and protein composition of bean leaf due to Bean yellow mosaic virus infection and salicylic acid treatments

The antioxidant status as well as protein composition of faba bean leaves infected with Bean yellow mosaic virus (BYMV) and the effect of salicylic acid application was examined in this paper. Some modifications in the antioxidant status were observed by changing some antioxidant enzymes activities and contents of antioxidant metabolites. BYMV-infected leaves revealed POD, CAT, APX and SOD induced activities while SA treatments could inhibit POD, CAT activities but induced SOD activity. The enzyme activities seemed to be SA concentration dependant. Higher H2O2 and MDA concentrations were recorded in virus-infected leaves than those of the corresponding controls while treatment with SA followed by virus inoculation caused lowering of MDA concentration and reducing the damage due to lipid peroxidation. Moreover, because of virus infection and/or SA treatments, an increase in the amounts of phenolics and flavonoids was noticed. As compared to the control, BYMV infection or SA application caused pronounced increase in the antioxidant activity of leaf extracts detected by DPPH assay, indicating an increase in the amounts of antioxidant compounds occurred. To test the protein composition, the contents of each protein fractions (soluble, insoluble and total) were analyzed and the change in protein patterns was visualized using SDS-PAGE. The BYMV-infected bean leaves had protein contents higher than the control indicating accumulation of pathogenesis-related proteins. Moreover, spraying SA with or without virus inoculation could accumulate soluble, insoluble and total proteins and the pattern of increase was in accordance with SA concentration. Alterations in protein patterns were observed in faba bean leaves (Vicia faba cv Giza 461) in response to BYMV infection and SA treatments. Because of BYMV infection and SA treatments, the protein profiles showed new bands in comparison to the control. Some polypeptides were highly accumulated in treatments of SA followed by virus inoculation. Changing antioxidant status and accumulation of some antioxidant metabolites as well as the pronounced alterations in the protein composition indicate a kind of plant response against pathogen invasion and in case of SA treatment it is considered a way by which a defence response was initiated and/or activated.