Dissecting the components controlling root‐to‐shoot arsenic translocation in <i>Arabidopsis thaliana</i>

Summary Arsenic (As) is an important environmental and food‐chain toxin. We investigated the key components controlling As accumulation and tolerance in Arabidopsis thaliana . We tested the effects of different combinations of gene knockout, including arsenate reductase ( HAC 1 ), γ‐glutamyl‐cysteine synthetase (γ ‐ ECS ), phytochelatin synthase ( PCS 1 ) and phosphate effluxer ( PHO 1 ), and the heterologous expression of the As‐hyperaccumulator Pteris vittata arsenite efflux ( Pv ACR 3 ), on As tolerance, accumulation, translocation and speciation in A. thaliana . Heterologous expression of Pv ACR 3 markedly increased As tolerance and root‐to‐shoot As translocation in A. thaliana , with Pv ACR 3 being localized to the plasma membrane. Combining Pv ACR 3 expression with HAC 1 mutation led to As hyperaccumulation in the shoots, whereas combining HAC 1 and PHO 1 mutation decreased As accumulation. Mutants of γ‐ ECS and PCS 1 were hypersensitive to As and had higher root‐to‐shoot As translocation. Combining γ‐ ECS or PCS 1 with HAC 1 mutation did not alter As tolerance or accumulation beyond the levels observed in the single mutants. Pv ACR 3 and HAC 1 have large effects on root‐to‐shoot As translocation. Arsenic hyperaccumulation can be engineered in A. thaliana by knocking out the HAC 1 gene and expressing Pv ACR 3 . Pv ACR 3 and HAC 1 also affect As tolerance, but not to the extent of γ‐ ECS and PCS 1.