Changes in the pattern of antioxidant enzymes in wheat exposed to water deficit and rewatering

Antioxidant defenses in two wheat cultivars differing in sensitivity to dehydration (YouJian (YJ-24) more sensitive than LongChun (LC-20) were analyzed during water deficit and rewatering. Resistant cultivar (LC-20) showed a higher relative water content than the sensitive cultivar (YJ-24) during the whole period of water withholding. In order to analyze the changes of antioxidant enzymes, native PAGE analysis of protein extract were performed. Wheat leaves had two isoforms of Mn-superoxide dismutase (SOD), two isoforms of Cu/Zn-SOD and one of Fe-SOD. Three catalase (CAT) isoforms were identified in the leaves of wheat. The activities of SOD and CAT isoforms were increased in two cultivars under water deficit. The intensities of SOD and CAT isoforms were slightly lower in LC-20 and increased continuously in YJ-24 after rewatering. Peroxidase (POD) isoforms were significantly increased during the whole dehydration-rehydration period. Three ascorbate peroxidase (APX) isoforms were present in gel. APX-1 and APX-3 were enhanced during water deficit and decreased during rewatering in LC-20. In YJ-24 only the activities of APX-2 were increased under water deficit. Seven isoforms of glutathione reductase (GR) were detected in the native gel. Activities of most of GR isoforms were higher in tolerant (LC-20) than in sensitive cultivar (YJ-24). Different isoforms of GR in two wheat cultivars behaved differently under water deficit and rewatering. These results collectively suggest that water deficit activates the SOD, CAT and ascorbate-glutathione cycle in wheat leaves. The response of enzyme isoforms to drought is not the same for all isoforms of antioxidant enzymes in two wheat cultivars.