Differential activity and expression of antioxidant enzymes and alteration in osmolyte accumulation under high temperature stress in wheat seedlings

• Antioxidant enzyme-related gene expression was more sensitive to HT stress.
• Fe-SOD and Mn-SOD might play important roles in SOD activity under HT stress.
• HT-resistant wheat cultivars had higher proline content.

The objective of this study was to investigate the effects of high temperature (HT) stress on activity and expression of antioxidant enzymes and osmotic adjustment substance content in seedlings of four wheat cultivars with contrasting levels of HT tolerance. The results showed that the differences in superoxide dismutase (SOD) activity, glutathione reductase (GR) activity, soluble protein content and proline content between HT-resistant cultivars and HT-sensitive cultivars were more obvious than those in the activities of peroxidase (POD) and catalase (CAT). Moreover, the transcript levels of Fe-SOD and Mn-SOD were consistent with the trend of variation in SOD activity, which suggested that Fe-SOD and Mn-SOD might play important roles in SOD activity under HT stress. Finally, the transcript levels of CAT and GR were more sensitive than the activities of CAT and GR in response to HT stress in wheat seedlings. Collectively, our results indicated that HT-resistant wheat cultivars had higher SOD activity, GR activity and proline content than HT-sensitive wheat cultivars under HT stress. These data indicated that HT-resistant wheat cultivars resisted the damage caused by HT stress more effectively, which could be applied in predicting HT-resistant wheat cultivars used for field production.