Sulfur dioxide enhance drought tolerance of wheat seedlings through HS signaling.

Drought is one of the most common factors that limit plant growth and productivity. Sulfur dioxide (SO) has recently been found to play a benefical role in protection of plants against environmental stress. In this study, we investigated the effect of SO on the physiological and molecular response of wheat seedlings to drought stress. Pretreatment with 10 mg/m SO significantly increased the survival rate and relative water content (RWC) of wheat seedlings under drought stress, indicating that pre-exposure to appropriate level of SO could enhance drought tolerance of plants. These responses were related to the enhanced proline accumulation in the drought-treated wheat seedlings that induced by SO pretreatment. Meanwhile, SO pretreatment increased the activities of superoxide dismutase (SOD) and peroxidase (POD), and effectively reduced the content of hydrogen peroxide (HO) and malondialdehyde (MDA) in drought-treated wheat seedlings, suggesting SO could alleviate drought-induced oxidative damage by enhancing antioxidant defense system in plants. Expression analysis of transcription factor genes also showed that SO pretreatment decreased the expression of TaNAC69, but the expression of TaERF1 and TaMYB30 changed slightly and maintained at higher levels in wheat seedlings in response to drought stress. Furthermore, SO pretreatment triggered marked accumulation of hydrogen sulfide (HS) in wheat seedlings under drought stress. When scavenged HS by spraying Hypotaurine (HT), the activities of antioxidant enzymes and the expression of transcription factor genes were decreased, and the content of HO and MDA increased to the level of drought treatment alone, suggesting a regulatory role of SO-induced HS in plant adaptation to drought stress. Together, this study indicated that SO enhanced drought tolerance of wheat seedlings through HS signaling, and provided new strategy for enhancing plant tolerance to drought stress.