Plant-specific actin binding protein that bundles and stabilizes microfilaments (MFs). Has no nucleation or capping activity. Regulates MF reorganization during stomatal closure. The binding to F-actin is insensitive to Ca(2+) and pH. Binds weakly to inositol phosphates (PubMed:22356912). Dimer. Dimerization is required for actin-binding activity. Expressed in roots, stems, leaves, flowers, siliques and guard cells. The NT5 region (73-100) is required for actin-binding activity. Defect in stomatal movment and hypersensitivity to drought stress. Belongs to the SCAB family.