Heterologous expression of Pteris vittata ACR3 promotes arsenic tolerance but not accumulation in Arabidopsis

Alyssa Marie DeLeon, Purdue University

Abstract

Arsenic is a class 1 carcinogen that causes widespread chronic human health issues due to the consumption of arsenic-contaminated groundwater and plant-based products. The Chinese brake fern Pteris vittata has the unique ability to hyperaccumulate arsenic to > 1% dry weight in the fronds. In P. vittata gametophytes, the vacuolar protein ACR3 is necessary for arsenic tolerance and localizes to the tonoplast where it is thought to confer tolerance by effluxing arsenite from the cytoplasm into the vacuole for sequestration. ACR3 homologs are missing in angiosperms. When heterologously expressed in Arabidopsis thaliana, P. vittata ACR3 localizes to the plasma membrane and promotes arsenic tolerance, as measured by increased root length and shoot biomass on both As(III) and As(V) media compared to wild-type. Furthermore, transgenic lines expressing P. vittata ACR3 accumulate less arsenic in roots and shoots compared to wild-type plants. Reciprocally-grafted plants expressing ACR3 in the root only (but not those expressing ACR3 in the shoot only) show increased arsenic tolerance, suggesting that ACR3 acts primarily in the root to promote arsenic tolerance and decrease arsenic accumulation. Results suggest that heterologous P. vittata ACR3 expression confers the ability to efflux As(III) from the cytoplasm of Arabidopsis root cells, increasing arsenic tolerance and reducing accumulation in root and shoot tissues. These findings may have important implications for developing transgenic crops that accumulate less arsenic or for developing phytoremediation systems.

Degree

M.S.

Advisors

Banks, Purdue University.

Subject Area

Plant biology

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