Malate-sensitive anion transporter permeable to chloride, nitrate, sulfate and malate. Involved in dark-, CO(2)-, abscisic acid- and water-deficient-induced stomatal closure. Belongs to the R-type anion channels. PubMed:20626656 indicates also a not confirmed endomembrane localization. The splice variants are not functional as anion transporters. Expressed in roots, stems, leaves, flowers and pollen. Mainly detected in the roots vascular stele and in the leaves guard cells. Not induced by aluminum. Impaired stomatal closure resulting in a wilty phenotype. Malate functions as a gating modifier as well as a permeating substrate. Belongs to the aromatic acid exporter (TC 2.A.85) family.