Water channel required to facilitate the transport of water across cell membrane; mercury-insensitive. Widely expressed, except in seeds. By dehydration (Ref.1). Not affected by water stress (PubMed:7846153). Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Belongs to the MIP/aquaporin (TC 1.A.8) family. PIP (TC 1.A.8.11) subfamily.