Variation in antioxidant isozymes contributes to variation in salt tolerance in rice genotypes

Abstract

Rice is a salt-sensitive crop and degree of salt sensitivity varies genotype to genotype. This is a result of existence of combination of mechanisms among genotypes. Salt-induced oxidative stress leads to the loss of membrane integrity and this may affect efficiency of mechanisms which contribute to salt tolerance. Antioxidant enzymes such as superoxide dismutase (SOD) and peroxidases (POXs) are known to be a part of oxidative stress tolerance mechanism. Their contribution in conferring salt tolerance and their individual isoform response was analyzed among genotypes with varying salt tolerance. The total antioxidant enzyme activity of SOD and POX was found to be genotype specific rather than salt tolerance level. Some of the isozymes of Cu/Zn SOD were found to be salt stress induced whereas chloroplastic and cytosolic Cu/Zn SOD isozyme activity found to be affected in most of the salt sensitive genotypes. Affected Cu/Zn SOD isozyme’s activity might have enhanced salt sensitivity of genotypes. Transcript profiling of individual SOD isoforms revealed the variation in basal level transcript abundance and differential response of each isoform even among genotypes with similar STG.