Aquaporins facilitate the transport of water and small neutral solutes across cell membranes. A number of isoforms are produced. According to EST sequences. Predominantly expressed in roots and green siliques. Also expressed above ground and in flower buds. 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.