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 panicles and flowers. Expressed in the growing regions of roots, internodes and leaves. By gibberellin (GA3) and wounding. Belongs to the expansin family. Expansin A subfamily.