Physio-Biochemical and Transcriptional Responses to Heat Stress in Seedlings Following Carbon Ion Beam Irradiation of Arabidopsis Seeds

Heat stress has become a major threat to plant growth and development. The objective of the present study was to investigate any changes in physio-biochemical and transcriptional seedling responses to heat stress caused by pre-stress irradiation of Arabidopsis seeds with a carbon ion beam. The seeds were exposed to a series of doses (0, 50, 100, 150, and 200 Gray [Gy]) before being exposed to heat stress (40 °C). The results showed that 50-Gy carbon ion beam irradiation exhibited stimulatory effects, compared with seedlings grown from non-irradiated seeds, on germination index, root length, and fresh weight in heat-stressed Arabidopsis seedlings. Moreover, the accumulation rates of superoxide anion radicals, hydroxyl radicals, hydrogen peroxide, and malondialdehyde concentrations were significantly lower in stressed seedlings grown from irradiated seeds. Furthermore, antioxidant enzyme activities and non-enzymatic antioxidant concentrations in heat-stressed seedlings grown from irradiated seed were significantly higher than in the control seedlings grown from non-irradiated seedlings. Notably, the transcription levels of several genes related to heat stress response were differentially regulated in response to heat stress in seedlings grown from seed irradiated with low-dose carbon ion beams. Collectively, this study suggests that low-dose carbon ion beam irradiation can modulate the physiological responses and regulate heat-signaling genes involved in mitigating heat stress during Arabidopsis seedling growth.