Arsenic is a ubiquitous environmental contaminant of food and water that threatens the health of tens of millions people world-wide. It is a toxin and carcinogen that comes from both minerals and anthropogenic use of arsenic-containing herbicides and animal growth promoters, as well as industrial use for semiconductors.
The major source of dietary arsenic is from eating plants that have accumulated arsenic. How arsenic is taken into roots and shoots is well understood, while little is known about how arsenic gets into seeds such as the rice grain.
ZHU Yongguan from Research Center for Eco-Environmental Sciences of Chinese Academy of Sciences collaborating with scientists from Germany and the United States identified how arsenic gets into the seeds of the plant Arabidopsis thaliana, which is used as a model for food plants. The study was published in Nature Plants.
The researchers discovered that the plant uses transport systems for the sugar alcohol inositol to load arsenite, the toxic form of arsenic. When either of two inositol transporter genes was expressed in the common baker yeast Saccharomyces cerevisiae, the yeast had increased arsenite accumulation and was killed by lower amounts of arsenite than normal yeast. They used A. thaliana plants lacking either gene and showed that the mutant plants accumulated much less arsenic in their phloem, the “arteries” of plants, their seed coats and, ultimately, in their seeds. The results demonstrated that inositol transporters are responsible for arsenite loading into phloem, the key step regulating arsenic accumulation in seeds.
This study is the first identification of transporters responsible for arsenic loading into plant "arteries"- the phloem. If these findings are proved to be applicable to rice, inositol transporters may be candidates for future developing new cultivars, which accumulate lower amounts of arsenic in their grain without affecting yield production, a major advance toward mitigation of the global health risks posed by arsenic in rice.
Laboratory of Soil Environmental Science
December 22, 2015