Salicylic acid modulates isoenzyme pattern of enzymatic antioxidants in wheat

Abstract

The isoenzyme profile of leaf and root tissues of wheat plants grown with different concentrations of salicylic acid (SA) was studied by native polyacrylamide gel electrophoresis (PAGE). Wheat plants were co-cultivated with different concentration of SA (0, 50, 500 and 1000 µM) in Hogland solution. Primary leaves and roots from one week old plants were used for the extraction of enzymes. The crude enzyme extracts were subjected to native PAGE and were stained for the enzymatic antioxidants catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and superoxide dismutase (SOD). Three isoforms of CAT were observed in both leaf and root tissues of which the intensity of major isoform was reduced in leaf tissues of plants grown with 1000 µM SA where as induction in band intensity of two minor isoforms were noticed in root tissues of plants grown with 500 and 1000 µM SA. The native-PAGE for peroxidase activity revealed five isoforms in root and two in leaf tissues. One of these isoforms in both the tissues showed a gradual reduction in activity with each concentration of SA. Band intensity of APX isoforms were found to be decreased in both leaf and root tissues of plants grown with 500 and 1000 µM SA. A stimulation in band intensity of two of the APX isoforms was noticed in plants grown with 50 µM SA. The isoenzyme profile of SOD revealed two iso-isoforms in leaf tissues and three isoforms in root tissues of both control and SA grown plants. Inhibitory test confirmed these isoenzymes as Cu/Zn-SOD. The study suggested that the effect of SA on the isoenzyme profile of wheat plants is tissue specific and also varies for different enzymes. The low concentration of SA stimulates the synthesis some isoforms where as the higher concentration has negative effect on the synthesis of some isoforms of enzymatic antioxidants.