Together with STR, required for arbuscule development in arbuscular mycorrhizal symbiosis. Heterodimerizes with STR; the resulting transporter is located in the peri-arbuscular membrane. Located in the peri-arbuscular membrane of arbuscular mycorrhiza (AM). Expressed constitutively in the vascular tissue of roots. Accumulates in root cortical cells containing arbuscules upon arbuscular mycorrhizal (AM) symbiosis with Glomus versiforme. Stunted arbuscule phenotype due to an impaired arbuscule development during arbuscular mycorrhizal (AM) symbiosis with Glomus versiforme; normal initial phases of the symbiosis, including hyphopodia formation and fungal entry into the cortex, as well as normal arbuscule development initiation, including arbuscule-associated genes expression, but strongly delayed and impaired arbuscule development (PubMed:20453115). Normal nodulation in the presence of Sinorhizobium meliloti (PubMed:20453115). Belongs to the ABC transporter superfamily. ABCG family. Stunted arbuscule (STR) subfamily.