As(III)-oxidizing bacteria alleviate arsenite toxicity via reducing As accumulation, elevating antioxidative activities and modulating ionome in rice (Oryza sativa L.)

Abstract

Abstract Compared to other crops, paddy rice trends to accumulate more arsenic (As) from soils. The toxicity and mobility of As mainly depended on its chemical species. To mitigate As(III) stress to rice plants, As(III)-oxidizing strain SMS11 isolated from As-contaminated soils was employed in the current study. The rice seedlings were hydroponically cultivated in three groups: Control Group (without any addition), As(III) group (amended with 1 mg∙L-1 As(III)) and As(III)+B group (treated with As(III) and As(III)-oxidizing bacteria). Compared to Control group, the growth of rice shoots from As(III) group was significantly restricted. Inoculation with the bacteria could not only enhance the growth of the rice plants, but also significantly reduce the As level in the rice shoots. Evaluation of oxidative stress indices showed that superoxide dismutase activity in the rice plants was enhanced under As(III) stress, resulting in promoted inhibition ability of superoxide anion radical (O2•−). The activity of catalase in the rice shoots was weakened when exposed to As(III), increasing the risk of hydroxyl radical (•OH) formation. When co-cultivated with the bacteria, •OH formation was significantly inhibited in the rice shoots. Uptake of As elevated most nutrient element contents in the rice shoots simultaneously. The levels of most nutrient elements in the rice shoots were declined with alleviation of As stress after inoculation with the bacteria. The ionomics of the rice plants revealed significant variations with tissues and environmental conditions. The results represented ionomic profile as a promising tool to identify rice plants under different external conditions.