Abstract
Aquaporins are membrane proteins that facilitate membrane transport of water and other small molecules in various organisms. Arabidopsis has 35 isoforms of aquaporins, which are classified into four subfamilies (PIPs, TIPs, NIPs, and SIPs) . In this study, we focused on four NIPs (NIP1;1, 1;2, 5;1, and 6;1) that have not been studied extensively yet, and investigated their water permeability, subcellular localization, and tissue-specific accumulation.
A stopped-flow spectrophotometric assay of the membrane vesicles from yeast cells harboring NIPs revealed that the four members had only low water permeability. The transient expression of NIP1;1, 1;2, and 6;1 linked with green fluorescent protein in Arabidopsis cultured cells showed their localization on the ER membrane. In addition, we performed promoter-β-glucuronidase (GUS) analysis to examine tissue-specific accumulation.
