Arsenic-Driven Trafficking of ACR3 Transporters Is Conserved across Plant Lineages

Abstract

Arsenic contamination poses a major environmental and public health challenge. In liverworts and ferns, ACR3 transporters mediate arsenite efflux and contribute to arsenic tolerance. We recently showed that ACR3 from Marchantia polymorpha (MpACR3) contains an extended N-terminal region that couples arsenic sensing to membrane trafficking. However, the function and regulation of ACR3 transporters across photosynthetic lineages remain unclear. Here, we characterize ACR3 transporters from phylogenetically distant algae and land plants using heterologous expression in yeast. All examined ACR3 proteins function as arsenic efflux transporters but display two distinct trafficking modes: constitutive plasma membrane localization or metalloid-driven relocalization from the endomembrane system. Like the previously characterized MpACR3, we show that this inducible trafficking is governed by an extended N-terminal domain unique to plant ACR3 proteins, integrating a conserved di-arginine ER/Golgi retention signal with cysteine-based arsenic sensing. These findings establish a direct mechanistic link between metalloid perception and subcellular targeting. Functional assays in Arabidopsis thaliana demonstrated that Physcomitrium patens ACR3 confers arsenic tolerance, reduces root arsenic accumulation, and retains metalloid-dependent trafficking, supporting its physiological relevance. Together, our findings uncover a conserved mechanism linking arsenic sensing to ACR3 trafficking and provide new insight into the evolution of arsenic tolerance in plants. Summary statementPlant ACR3 transporters mediate arsenic efflux and exhibit distinct trafficking modes. An N-terminal domain links arsenic sensing to the endomembrane system-plasma membrane relocalization, revealing a conserved mechanism controlling ACR3 function and arsenic tolerance across plant lineages.