title: A new LxxxA motif in the transmembrane Helix3 of maize aquaporins belonging to the plasma membrane intrinsic protein PIP2 group is required for their trafficking to the plasma membrane.
abstract: Aquaporins play important roles in maintaining plant water status under challenging environments. The regulation of aquaporin density in cell membranes is essential to control transcellular water flows. This work focuses on the maize (Zea mays) plasma membrane intrinsic protein (ZmPIP) aquaporin subfamily, which is divided into two sequence-related groups (ZmPIP1s and ZmPIP2s). When expressed alone in mesophyll protoplasts, ZmPIP2s are efficiently targeted to the plasma membrane, whereas ZmPIP1s are retained in the endoplasmic reticulum (ER). A protein domain-swapping approach was utilized to demonstrate that the transmembrane domain3 (TM3), together with the previously identified N-terminal ER export diacidic motif, account for the differential localization of these proteins. In addition to protoplasts, leaf epidermal cells transiently transformed by biolistic particle delivery were used to confirm and refine these results. By generating artificial proteins consisting of a single transmembrane domain, we demonstrated that the TM3 of ZmPIP1;2 or ZmPIP2;5 discriminates between ER and plasma membrane localization, respectively. More specifically, a new LxxxA motif in the TM3 of ZmPIP2;5, which is highly conserved in plant PIP2s, was shown to regulate its anterograde routing along the secretory pathway, particularly its export from the ER.
authors.affiliation: Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Adrien S
authors.initials: AS
authors.lastname: Chevalier
authors.affiliation: Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Gerd Patrick
authors.initials: GP
authors.lastname: Bienert
authors.affiliation: Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium francois.chaumont@uclouvain.be.
authors.forename: François
authors.initials: F
authors.lastname: Chaumont
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D020346:Aquaporins / Q000737:chemistry / Q000378:metabolism*; D019470:Biolistics; D008969:Molecular Sequence Data; D005810:Multigene Family; D010940:Plant Proteins / Q000378:metabolism*; D020033:Protein Isoforms; D021381:Protein Transport; D055571:Secretory Pathway; D003313:Zea mays / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D020033:Protein Isoforms; C110065:major intrinsic protein, plant