Arsenite phytotoxicity and metabolite redistribution in lettuce (Lactuca sativa L.)

Arsenic (As) contamination has become a global problem, especially in developing countries, where a significant percentage of the population depends on groundwater for drinking. Arsenic toxicity depends on its chemical form. Herein, we evaluated the phytotoxicity of arsenite [As(III)], including As accumulation and adverse physiological responses (e.g., growth inhibition, oxidative stress, and metabolic disturbances). Furthermore, this result was compared with the mechanism of the phytotoxicity of arsenate [As(V)] that we previously explored. As accumulated mainly in the roots (29.33-88.73 mg/kg) of lettuce, only a small amount was transferred to the leaves (0.08-0.22 mg/kg); arsenic mainly existed in the form of As(III) in plants. As(III) was positively correlated with Mn in the leaves and roots and negatively correlated with Ca in roots and Mg in leaves, consistent with the increase in SOD activity and the destruction of the chloroplast membrane. Plants responded differently to As(III) and As(V) in terms of the antioxidant response and metabolic response. CAT activity in leaves was reduced following As(III) exposure and increased upon As(V) exposure. Furthermore, As(III) decreased the levels of some products of the tricarboxylic acid cycle and induced abnormal metabolism of secondary metabolites, such as phenol and niacin. The present study explored arsenic accumulation induced by As(III), the related physiological and biochemical responses and subsequent metabolite redistribution, and provided insights into the effects of different As species on plants.