Katsuhara Maki, Hanba Yuko T, Shiratake Katsuhiro, Maeshima Masayoshi
Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan.
Centre for Bioresource Field Science, Kyoto Institute of Technology, Kyoto 616-8354, Japan.
Funct Plant Biol. 2008 Feb;35(1):1-14. doi: 10.1071/FP07130.
Aquaporins facilitate water transport across biomembranes in a manner dependent on osmotic pressure and water-potential gradient. The discovery of aquaporins has facilitated research on intracellular and whole-plant water transport at the molecular level. Aquaporins belong to a ubiquitous family of membrane intrinsic proteins (MIP). Plants have four subfamilies: plasma-membrane intrinsic protein (PIP), tonoplast intrinsic protein (TIP), nodulin 26-like intrinsic protein (NIP), and small basic intrinsic protein (SIP). Recent research has revealed a diversity of plant aquaporins, especially their physiological functions and intracellular localisation. A few PIP members have been reported to be involved in carbon dioxide permeability of cells. Newly identified transport substrates for NIP members of rice and Arabidopsis thaliana have been demonstrated to transport silicon and boron, respectively. Ammonia, glycerol, and hydrogen peroxide have been identified as substrates for plant aquaporins. The intracellular localisation of plant aquaporins is diverse; for example, SIP members are localised on the ER membrane. There has been much progress in the research on the functional regulation of water channel activity of PIP members including phosphorylation, formation of hetero-oligomer, and protonation of histidine residues under acidic condition. This review provides a broad overview of the range of potential aquaporins, which are now believed to participate in the transport of several small molecules in various membrane systems in model plants, crops, flowers and fruits.
水通道蛋白以依赖渗透压和水势梯度的方式促进水跨生物膜的运输。水通道蛋白的发现推动了在分子水平上对细胞内和整株植物水分运输的研究。水通道蛋白属于一个普遍存在的膜内在蛋白（MIP）家族。植物有四个亚家族：质膜内在蛋白（PIP）、液泡膜内在蛋白（TIP）、结节蛋白26样内在蛋白（NIP）和小碱性内在蛋白（SIP）。最近的研究揭示了植物水通道蛋白的多样性，尤其是它们的生理功能和细胞内定位。据报道，一些PIP成员参与细胞的二氧化碳通透性。已证实水稻和拟南芥的NIP成员新鉴定的转运底物分别运输硅和硼。氨、甘油和过氧化氢已被确定为植物水通道蛋白的底物。植物水通道蛋白的细胞内定位多种多样；例如，SIP成员定位于内质网膜上。在PIP成员水通道活性的功能调节研究方面取得了很大进展，包括磷酸化、异源寡聚体的形成以及酸性条件下组氨酸残基的质子化。本综述广泛概述了潜在水通道蛋白的范围，现在认为它们参与了模式植物、作物、花卉和果实中各种膜系统中几种小分子的运输。
