Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), and ‡Department of Plant Physiology, University of Bayreuth , Universitätsstrasse 30, 95447 Bayreuth, Germany.
Environ Sci Technol. 2017 Jun 20;51(12):7187-7196. doi: 10.1021/acs.est.6b06028. Epub 2017 Jun 2.
Thioarsenates form from arsenite under sulfate-reducing conditions, e.g., in rice paddy soils, and are structural analogues of arsenate. Even though rice is one of the most important sources of human arsenic intake, nothing is published about uptake, toxicity, or tolerance of thioarsenates in plants. Experiments using the model system Arabidopsis thaliana showed that monothioarsenate is less toxic than arsenite, but more toxic than arsenate at concentrations ≥25 μM As, reflected in stronger seedling growth inhibition on agar plates. Despite higher toxicity, total As accumulation in roots was lower upon exposure to monothioarsenate compared to arsenate, and a higher root efflux was confirmed. Root-shoot translocation was higher for monothioarsenate than for arsenate. Compared to the wild type (Col-0), both arsenate and monothioarsenate induced higher toxicity in phytochelatin (PC)-deficient mutants (cad1-3) as well as in glutathione biosynthesis (cad2) and PC transport (abcc12) mutants, demonstrating the important role of the PC pathway, not only for arsenate, but also for monothioarsenate detoxification. In Col-0, monothioarsenate induced relatively higher accumulation of PCs than arsenate. The observed differences in plant uptake, toxicity, and tolerance of thioarsenate vs oxyarsenate show that studying the effects of As on plants should include experiments with thiolated As species.
在硫酸盐还原条件下，硫代砷酸盐由亚砷酸盐形成，例如在稻田土壤中，是砷酸盐的结构类似物。尽管水稻是人类摄入砷的最重要来源之一，但目前尚无关于植物中硫代砷酸盐的吸收、毒性或耐受性的报道。使用拟南芥模型系统进行的实验表明，单硫代砷酸盐的毒性低于亚砷酸盐，但在浓度≥25 μM As 时，毒性高于砷酸盐，这反映在琼脂平板上对幼苗生长的抑制更强。尽管毒性更高，但与砷酸盐相比，暴露于单硫代砷酸盐时根中的总砷积累较低，并且确认了更高的根外排。根到茎的转运对于单硫代砷酸盐来说比砷酸盐更高。与野生型（Col-0）相比，砷酸盐和单硫代砷酸盐在植物螯合肽（PC）缺陷突变体（cad1-3）以及谷胱甘肽生物合成（cad2）和 PC 转运（abcc12）突变体中诱导更高的毒性，这表明 PC 途径不仅对砷酸盐，而且对单硫代砷酸盐解毒都具有重要作用。在 Col-0 中，单硫代砷酸盐诱导的 PC 积累比砷酸盐相对更高。与氧代砷酸盐相比，植物对硫代砷酸盐的吸收、毒性和耐受性的观察到的差异表明，研究 As 对植物的影响应包括含硫代 As 物种的实验。
