Irradiation with low-dose gamma ray enhances tolerance to heat stress in Arabidopsis seedlings

• 50-Gy gamma irradiation promotes the growth of heat-stressed Arabidopsis seedling.
• 50-Gy gamma irradiation markedly reduces the level of ROS and MDA under heat stress.
• 50-Gy gamma irradiation stimulates antioxidant enzyme and GSH under heat stress.
• Proline is markedly accumulated under low-dose gamma irradiation under heat stress.
• Low-dose gamma rays regulate the expression of genes related to thermotolerance.

Gamma irradiation at low doses can stimulate the tolerance to environmental stress in plants. However, the knowledge regarding the mechanisms underlying the enhanced tolerance induced by low-dose gamma irradiation is far from fully understood. In this study, to investigate the physiological and molecular mechanisms of heat stress alleviated by low-dose gamma irradiation, the Arabidopsis seeds were exposed to a range of doses before subjected to heat treatment. Our results showed that 50-Gy gamma irradiation maximally promoted seedling growth in response to heat stress. The production rate of superoxide radical and contents of hydrogen peroxide and malondialdehyde in the seedlings irradiated with 50-Gy dose under heat stress were significantly lower than those of controls. The activities of antioxidant enzymes, glutathione (GSH) content and proline level in the gamma-irradiated seedlings were significantly increased compared with the controls. Furthermore, transcriptional expression analysis of selected genes revealed that some components related to heat tolerance were stimulated by low-dose gamma irradiation under heat shock. Our results suggest that low-dose gamma irradiation can modulate the physiological responses as well as gene expression related to heat tolerance, thus alleviating the stress damage in Arabidopsis seedlings.