title: Control of the Water Transport Activity of Barley HvTIP3;1 Specifically Expressed in Seeds.
abstract: Tonoplast intrinsic proteins (TIPs) are involved in the transport and storage of water, and control intracellular osmotic pressure by transporting material related to the water potential of cells. In the present study, we focused on HvTIP3;1 during the periods of seed development and desiccation in barley. HvTIP3;1 was specifically expressed in seeds. An immunochemical analysis showed that HvTIP3;1 strongly accumulated in the aleurone layers and outer layers of barley seeds. The water transport activities of HvTIP3;1 and HvTIP1;2, which also accumulated in seeds, were measured in the heterologous expression system of Xenopus oocytes. When they were expressed individually, HvTIP1;2 transported water, whereas HvTIP3;1 did not. However, HvTIP3;1 exhibited water transport activity when co-expressed with HvTIP1;2 in oocytes, and this activity was higher than when HvTIP1;2 was expressed alone. This is the first report to demonstrate that the water permeability of a TIP aquaporin was activated when co-expressed with another TIP. The split-yellow fluorescent protein (YFP) system in onion cells revealed that HvTIP3;1 interacted with HvTIP1;2 to form a heterotetramer in plants. These results suggest that HvTIP3;1 functions as an active water channel to regulate water movement through tissues during the periods of seed development and desiccation.
authors.affiliation: Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046 Japan utsugi@okayama-u.ac.jp.
authors.forename: Shigeko
authors.initials: S
authors.lastname: Utsugi
authors.affiliation: Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046 Japan.
authors.forename: Mineo
authors.initials: M
authors.lastname: Shibasaka
authors.affiliation: Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046 Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Maekawa
authors.affiliation: Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046 Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Katsuhara
mesh_terms: D001692:Biological Transport; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000378:metabolism*; D007150:Immunohistochemistry; D008954:Models, Biological; D008969:Molecular Sequence Data; D019697:Onions / Q000166:cytology; D009928:Organ Specificity / Q000235:genetics; D019441:Plant Epidermis / Q000166:cytology; D018515:Plant Leaves / Q000235:genetics; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D014867:Water
keywords: Aquaporin; Barley; Seed; TIP; Water transport activity