A number
of the aquaporin nodulin26-like intrinsic proteins (NIPs) are able to transport arsenite,
the predominant form of As in reducing environments. In rice (Oryza sativa), arsenite
uptake shares the highly efficient silicon (Si) pathway of entry to root cells and efflux
towards the xylem. In root cells arsenate is rapidly reduced to arsenite, which is
effluxed to the external medium, complexed by thiol peptides or translocated to
shoots. One type of arsenate reductase has been identified, but its in planta functions
remain to be investigated. Some fern species in the Pteridaceae family are able
to hyperaccumulate As in above-ground tissues. Hyperaccumulation appears to
involve enhanced arsenate uptake, decreased arsenite-thiol complexation and
arsenite efflux to the external medium, greatly enhanced xylem translocation of
arsenite, and vacuolar sequestration of arsenite in fronds. Current knowledge gaps
and future research directions are also identified.
A numberof the aquaporin nodulin26-like intrinsic proteins (NIPs) are able to transport arsenite,the predominant form of As in reducing environments. In rice (Oryza sativa), arseniteuptake shares the highly efficient silicon (Si) pathway of entry to root cells and effluxtowards the xylem. In root cells arsenate is rapidly reduced to arsenite, which iseffluxed to the external medium, complexed by thiol peptides or translocated toshoots. One type of arsenate reductase has been identified, but its in planta functionsremain to be investigated. Some fern species in the Pteridaceae family are ableto hyperaccumulate As in above-ground tissues. Hyperaccumulation appears toinvolve enhanced arsenate uptake, decreased arsenite-thiol complexation andarsenite efflux to the external medium, greatly enhanced xylem translocation ofarsenite, and vacuolar sequestration of arsenite in fronds. Current knowledge gapsand future research directions are also identified.
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