Discovery of transporters that regulate arsenic accumulation in Arabidopsis seeds

Arsenic contamination of groundwater and soils threatens the health of tens of millions of people worldwide. Understanding the way in which arsenic is taken up by crops such as rice, which is known to serve as a significant source of arsenic in the human diet, is therefore important. Membrane transport proteins––that catalyze arsenic uptake by roots, and translocation through the xylem to shoots––have been previously characterized in a number of plants, including rice.

The transporters responsible for loading arsenic from the xylem, into the phloem, and on into the seeds, however, are yet to be identified. In paper referenced below, authors show that transporters responsible for inositol uptake in the phloem in the small mustard Arabidopsis thalianaalso influx arsenic. Transformation of Saccharomyces cerevisiae (baker’s yeast) with AtINT2 or AtINT4 was shown to lead to increased arsenic accumulation and increased sensitivity to arsenite. Expression of AtINT2 in Xenopus laevis (African clawed frog) oocytes also resulted in increased arsenite import. Disruption of AtINT2 or AtINT4 in Arabidopsis thaliana caused a decrease in phloem, silique and seed arsenic concentrations in plants fed with arsenite through the roots, when compared with that in wild-type plants. These AtINT2 and AtINT4 knockout plants also exhibited a large drop in silique and seed arsenic concentrations when fed with arsenite through the leaves. Authors conclude that, in Arabidopsis, inositol transporters are responsible for arsenite loading into the phloem, the key source of arsenic in seeds.

Nat Plants 2o16; 1: 1–6

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