Plant Physiology, Bayreuth Center for Ecology and Environmental Research (BayCEER), University of Bayreuth, D-95440 Bayreuth, Germany.
Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), University of Bayreuth, D-95440 Bayreuth, Germany.
Environ Sci Technol. 2022 Jul 19;56(14):10072-10083. doi: 10.1021/acs.est.2c01206. Epub 2022 Jun 27.
Arsenic is one of the most relevant environmental pollutants and human health threats. Several arsenic species occur in soil pore waters. Recently, it was discovered that these include inorganic and organic thioarsenates. Among the latter, dimethylmonothioarsenate (DMMTA) is of particular concern because in mammalian cells, its toxicity was found to exceed even that of arsenite. We investigated DMMTA toxicity for plants in experiments with and indeed observed stronger growth inhibition than with arsenite. DMMTA caused a specific, localized deformation of root epidermal cells. Toxicity mechanisms apparently differ from those of arsenite since no accumulation of reactive oxygen species was observed in DMMTA-exposed root tips. Also, there was no contribution of the phytochelatin pathway to the DMMTA detoxification as indicated by exposure experiments with respective mutants and thiol profiling. RNA-seq analysis found strong transcriptome changes dominated by stress-responsive genes. DMMTA was taken up more efficiently than the methylated oxyarsenate dimethylarsenate and highly mobile within plants as revealed by speciation analysis. Shoots showed clear indications of DMMTA toxicity such as anthocyanin accumulation and a decrease in chlorophyll and carotenoid levels. The toxicity and efficient translocation of DMMTA within plants raise important food safety issues.
砷是一种最重要的环境污染物和人类健康威胁之一。土壤孔隙水中存在多种砷形态。最近，人们发现这些砷形态包括无机和有机硫代砷酸盐。在后者中，二甲基单硫代砷酸酯（DMMTA）特别令人担忧，因为在哺乳动物细胞中，其毒性甚至超过亚砷酸盐。我们用和进行了植物的 DMMTA 毒性实验，结果发现 DMMTA 对植物的生长抑制作用比亚砷酸盐更强。DMMTA 导致根表皮细胞的特定、局部变形。毒性机制显然与亚砷酸盐不同，因为在 DMMTA 暴露的根尖中没有观察到活性氧物质的积累。此外，如用相应的突变体和巯基谱进行的暴露实验所示，植物螯合肽途径对 DMMTA 解毒没有贡献。RNA-seq 分析发现，转录组发生了强烈的变化，主要由应激响应基因主导。与甲基化氧代砷酸盐二甲基砷酸盐相比，DMMTA 的摄取效率更高，在植物体内的迁移性也更强，这从形态分析中得到了证实。地上部分显示出 DMMTA 毒性的明显迹象，如花青素积累以及叶绿素和类胡萝卜素水平下降。DMMTA 在植物体内的毒性和高效转运引发了重要的食品安全问题。
