title: Methylated arsenic species in plants originate from soil microorganisms.
abstract: • Inorganic arsenic (iAs) is a ubiquitous human carcinogen, and rice (Oryza sativa) is the main contributor to iAs in the diet. Methylated pentavalent As species are less toxic and are routinely found in plants; however, it is currently unknown whether plants are able to methylate As. • Rice, tomato (Solanum lycopersicum) and red clover (Trifolium pratense) were exposed to iAs, monomethylarsonic acid (MMA(V)), or dimethylarsinic acid (DMA(V)), under axenic conditions. Rice seedlings were also grown in two soils under nonsterile flooded conditions, and rice plants exposed to arsenite or DMA(V) were grown to maturity in nonsterile hydroponic culture. Arsenic speciation in samples was determined by HPLC-ICP-MS. • Methylated arsenicals were not found in the three plant species exposed to iAs under axenic conditions. Axenically grown rice was able to take up MMA(V) or DMA(V), and reduce MMA(V) to MMA(III) but not convert it to DMA(V). Methylated As was detected in the shoots of soil-grown rice, and in rice grain from nonsterile hydroponic culture. GeoChip analysis of microbial genes in a Bangladeshi paddy soil showed the presence of the microbial As methyltransferase gene arsM. • Our results suggest that plants are unable to methylate iAs, and instead take up methylated As produced by microorganisms.
authors.affiliation: Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Lomax
authors.affiliation: Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.|College of Resources and Environmental Science, Hebei Agricultural University, Baoding, Hebei Province 071001, China.
authors.forename: Wen-Ju
authors.initials: WJ
authors.lastname: Liu
authors.affiliation: Institute for Environmental Genomics, University of Oklahoma, 101 David L. Boren Blvd, Norman, OK 73019, USA.
authors.forename: Liyou
authors.initials: L
authors.lastname: Wu
authors.affiliation: Institute for Environmental Genomics, University of Oklahoma, 101 David L. Boren Blvd, Norman, OK 73019, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Xue
authors.affiliation: Institute for Environmental Genomics, University of Oklahoma, 101 David L. Boren Blvd, Norman, OK 73019, USA.
authors.forename: Jinbo
authors.initials: J
authors.lastname: Xiong
authors.affiliation: Institute for Environmental Genomics, University of Oklahoma, 101 David L. Boren Blvd, Norman, OK 73019, USA.
authors.forename: Jizhong
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Steve P
authors.initials: SP
authors.lastname: McGrath
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Meharg
authors.affiliation: Department of Disease and Stress Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Miller
authors.affiliation: Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Fang-Jie
authors.initials: FJ
authors.lastname: Zhao
mesh_terms: D001151:Arsenic / Q000378:metabolism*; D001152:Arsenicals / Q000378:metabolism*; D018053:Arsenites / Q000633:toxicity; D061245:Axenic Culture; D001419:Bacteria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002101:Cacodylic Acid / Q000378:metabolism* / Q000633:toxicity; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D018527:Hydroponics; D018551:Solanum lycopersicum / Q000187:drug effects / Q000254:growth & development; D008745:Methylation / Q000187:drug effects; D020411:Oligonucleotide Array Sequence Analysis; D012275:Oryza / Q000187:drug effects / Q000254:growth & development; D063245:Plant Development; D010944:Plants / Q000187:drug effects / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000378:metabolism; D012987:Soil; D012988:Soil Microbiology; D029921:Trifolium / Q000187:drug effects / Q000254:growth & development
chemical_list: D001152:Arsenicals; D018053:Arsenites; D012987:Soil; D002101:Cacodylic Acid; C020300:monomethylarsonic acid; C015001:arsenite; D001151:Arsenic
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