May cause loosening and extension of plant cell walls by disrupting non-covalent bonding between cellulose microfibrils and matrix glucans. No enzymatic activity has been found. May be required for rapid internodal elongation in deepwater rice during submergence (By similarity). Expressed in the epidermis and vascular cylinder of the root tip, lateral root primordia, adventitious root primordia, shoot apex and leaf primordia. Expressed in the apical region (growing zone) of the root hair. Belongs to the expansin family. Expansin A subfamily.