Pretreatment with low-dose gamma irradiation enhances tolerance to the stress of cadmium and lead in Arabidopsis thaliana seedlings

• Low-dose gamma irradiation promotes Arabidopsis seedling growth under Cd/Pb stress.
• 50-Gy gamma irradiation decreases the contents of H2O2 and MDA under Cd/Pb stress.
• 50-Gy gamma irradiation stimulates antioxidant enzyme activities under Cd/Pb stress.
• 50-Gy gamma irradiation markedly induces proline accumulation under Cd/Pb stress.
• Low gamma rays regulate the expression of genes related to Cd/Pb resistance.

Heavy metals are important environmental pollutants with negative impact on plant growth and development. To investigate the physiological and molecular mechanisms of heavy metal stress mitigated by low-dose gamma irradiation, the dry seeds of Arabidopsis thaliana were exposed to a Cobalt-60 gamma source at doses ranging from 25 to 150 Gy before being subjected to 75 µM CdCl2 or 500 µM Pb(NO3)2. Then, the growth parameters, and physiological and molecular changes were determined in response to gamma irradiation. Our results showed that 50-Gy gamma irradiation gave maximal beneficial effects on the germination index and root length in response to cadmium/lead stress in Arabidopsis seedlings. The hydrogen peroxide and malondialdehyde contents in seedlings irradiated with 50-Gy gamma rays under stress were significantly lower than those of controls. The antioxidant enzyme activities and proline levels in the irradiated seedlings were significantly increased compared with the controls. Furthermore, a transcriptional expression analysis of selected genes revealed that some components of heavy metal detoxification were stimulated by low-dose gamma irradiation under cadmium/lead stress. Our results suggest that low-dose gamma irradiation alleviates heavy metal stress, probably by modulating the physiological responses and gene expression levels related to heavy metal resistance in Arabidopsis seedlings.