植物水通道蛋白的干旱应答机制研究进展

干旱胁迫是严重影响全球作物生产的非生物胁迫之一,研究植物耐旱机制已成为一个重要领域。水通道蛋白是一类特异、高效转运水及其它小分子底物的膜通道蛋白,在植物中具有丰富的亚型,参与调节植物的水分吸收和运输。近10年来,水通道蛋白在植物不同生理过程中的作用,一直受到研究人员的关注,特别是在非生物胁迫方面,而研究表明水通道蛋白在干旱胁迫下对植物的耐旱性起着至关重要的作用,能维持细胞水分稳态和调控环境胁迫快速响应。水通道蛋白在植物耐旱过程中的调控机制及功能较复杂,而关于其应答机制和不同亚型功能性研究的报道甚少。该文综述了植物水通道蛋白的分类、结构、表达调控和活性调节,分别从植物水通道蛋白响应干旱表达调控机制、水通道蛋白基因表达的时空特异性、水通道蛋白基因的表达与蛋白丰度,水通道蛋白基因的耐旱转化四个方面阐明干旱胁迫下植物水通道蛋白的表达,重点阐述其参与植物干旱胁迫应答的作用机制,并提出水通道蛋白研究的主要方向。     

植物水通道蛋白及其活性调节

水通道蛋白是对水专一的通道蛋白,普遍存在于动、植物及微生物中。研究表明高等植物的质膜和液泡膜上存在着丰富的水通道蛋白,其种类繁多,分布广泛,并具有一定的组织特异性。植物水通道蛋白的活性受到严格的调控,其调节方式主要有两种,分别为基因水平的表达调控和翻译后的修饰作用。     

植物水通道蛋白的运输和调节

水通道蛋白是细胞间和细胞内水分运输的主要通道,其运输和调控对于植物细胞的水分稳态和胁迫响应具有重要作用。本文综述了水通道蛋白运输的分子机制以及结构修饰、门控、膜转运和异源四聚体等调节机制。     

水通道蛋白在细胞中的调控

水通道蛋白是一个具有跨膜运输水分子功能的蛋白家族．其功能受到细胞精细调控,以维持细胞正常的生理状态,水通道蛋白异常将导致相关疾病的发生。重点介绍水通道蛋白在细胞中的调控机理。     

植物抗逆反应中水孔蛋白的表达调控研究

水孔蛋白(aquaporin,AQP)作为一种功能性跨膜输水蛋白,对植物体形成水选择性运输通道并实现水分的跨膜运输起到重要的作用.当植物处于盐、干旱、低温等逆境胁迫状态时,体内的水分平衡被打破,水孔蛋白在水分运输和胞内渗透压的调控等方面表现出重要作用.综述了植物抗逆反应中水孔蛋白表达调控的研究进展.     

水通道蛋白研究动态

水通道蛋白是对水专一的通道蛋白,它普遍存在于动、植物及微生物中,不同水通道蛋白之间具有类似特征.哺乳动物中水通道蛋白主要分为六类,分布于水分代谢活跃的器官中;植物除了质膜上水通道蛋白外,液泡膜也存在着水通道蛋白,它们在植物生长,发育及胁迫适应中起着重要作用.目前有关水通道蛋白的详细的结构和功能信息主要来自对红细胞膜上水通道蛋白的研究,它由同源的四聚体组成,每个单体具有独立的水通道功能,四聚体在膜上分布具有不对称性,在膜内侧四聚体呈伸展状态,在膜外侧形成大的中心空腔.     

藻类水通道蛋白的研究进展

目前,大量水通道蛋白已在古菌、细菌、真菌、动物和植物中相继被发现,但对于低等植物——藻类水通道蛋白的研究相对较少。藻类与陆地高等植物在生长环境方面存在较大差异,因此其体内存在的水通道蛋白在功能作用机制方面与高等植物会有不同。所有藻类的生长发育过程都与水分传导息息相关,而藻类水通道蛋白不仅仅是水分运输的通道蛋白,同时还具有其他生理生化功能,是一类多功能蛋白。与植物水通道蛋白相比,藻类水通道蛋白的研究起步较晚。在2004年从莱茵衣藻中得到第一个水通道蛋白后,越来越多的研究者开始对藻类体内存在的水通道蛋白产生关注。近年来,在一些藻类全基因组测序完成的基础之上,研究者对藻类水通道蛋白的探索也有了新的进展。迄今为止,已有8个不同亚族的藻类水通道蛋白被确定出来,而且在近两年内,又有研究者从南极冰藻、条斑紫菜和羊栖菜中发现新的藻类水通道蛋白。综述了当前藻类水通道蛋白的分类和结构特征等方面的研究进展,并结合新发现的几种藻类水通道蛋白,阐述了藻类处于胁迫环境时水通道蛋白的特异性表达和所发挥的生理功能,为后续相关藻类水通道蛋白的研究奠定一定的理论基础。     

植物的水通道蛋白

对近 3年来植物水通道蛋白的特性、特异性表达、水分运输机制、表达调控、在植物水分关系平衡中的作用以及这一领域研究中的有关问题作了介绍与评述     

番茄水通道蛋白基因家族的生物信息学分析

植物水通道蛋白不仅仅在根系输送水分,而是具有底物和细胞定位的多样性的基因家族,因而对植物生理和发育过程,包括种子发芽、侧根发生、碳固定和营养吸收等都有重要的贡献。番茄基因组中共有44个水通道蛋白基因。这些基因可分为TIP、PIP、NIP和SIP 4个亚家族。这4个亚家族具有不同的功能和亚细胞定位。在番茄十号染色体水通道蛋白聚集位点上的5个基因与一号染色体上的一个基因是直系同源水通道蛋白,相似度都很高,同属于PIP亚家族。番茄水通道蛋白大多在根部表达量较高,在茎、叶、花等部位表达较低。不过Solyc03g096290.2.1和Solyc01g094690.2.1基因在花中表达量最高。此外,有个别基因表达量稳定在较高的水平,包括Solyc06g074820.2.1和Solyc08g081190.2.1。这些基因的功能可能不仅是吸收和转运水分,是否有其他的转运底物,在植物抗逆和发育过程中是否有调控作用,是下一步研究的重点。番茄全基因组中的水通道蛋白进行检索和分析,对番茄分子生物学研究和种质改良都有重要的意义。     

植物液泡膜水通道蛋白的结构、分布和功能研究进展

植物液泡膜水通道蛋白(tonoplast intrinsic proteins, TIPs)是植物体内水分子和一些小分子溶质跨液泡膜运输的通道。TIPs介导胞内或胞间的水分跨膜运输,在维持植物细胞的水分平衡过程中起着至关重要的作用。由于TIPs特异的定位在液泡膜上,长久以来一直被用作不同植物物种和组织中液泡识别的标记物。本综述介绍了液泡膜水通道蛋白的发现、结构、分类以及亚细胞和组织定位、基因表达和蛋白功能等方面的研究进展,初步探讨了植物液泡膜水通道蛋白研究中存在的问题及今后的研究热点,希望能为相关的科研人员在研究液泡膜定位的水通道蛋白中提供帮助。     

The role of aquaporins in cellular and whole plant water balance

Aquaporins are water channel proteins belonging to the major intrinsic protein (MIP) superfamily of membrane proteins. More than 150 MIPs have been identified in organisms ranging from bacteria to animals and plants. In plants, aquaporins are present in the plasma membrane and in the vacuolar membrane where they are abundant constituents. Functional studies of aquaporins have hitherto mainly been performed by heterologous expression in Xenopus oocytes. A main issue is now to understand their role in the plant, where they are likely to be important both at the cellular and at the whole plant level. Plants contain a large number of aquaporin isoforms with distinct cell type- and tissue-specific expression patterns. Some of these are constitutively expressed, whereas the expression of others is regulated in response to environmental factors, such as drought and salinity. At the protein level, regulation of water transport activity by phosphorylation has been reported for some aquaporins.     

Overexpression of a plasma membrane aquaporin in transgenic tobacco improves plant vigor under favorable growth conditions but not under drought or salt stress

Most of the symplastic water transport in plants occurs via aquaporins, but the extent to which aquaporins contribute to plant water status under favorable growth conditions and abiotic stress is not clear. To address this issue, we constitutively overexpressed the Arabidopsis plasma membrane aquaporin, PIP1b, in transgenic tobacco plants. Under favorable growth conditions, PIP1b overexpression significantly increased plant growth rate, transpiration rate, stomatal density, and photosynthetic efficiency. By contrast, PIP1b overexpression had no beneficial effect under salt stress, whereas during drought stress it had a negative effect, causing faster wilting. Our results suggest that symplastic water transport via plasma membrane aquaporins represents a limiting factor for plant growth and vigor under favorable conditions and that even fully irrigated plants face limited water transportation. By contrast, enhanced symplastic water transport via plasma membrane aquaporins may not have any beneficial effect under salt stress, and it has a deleterious effect during drought stress.     

Major intrinsic proteins (MIPs) in plants: a complex gene family with major impacts on plant phenotype

The ubiquitous cell membrane proteins called aquaporins are now firmly established as channel proteins that control the specific transport of water molecules across cell membranes in all living organisms. The aquaporins are thus likely to be of fundamental significance to all facets of plant growth and development affected by plant–water relations. A majority of plant aquaporins have been found to share essential structural features with the human aquaporin and exhibit water-transporting ability in various functional assays, and some have been shown experimentally to be of critical importance to plant survival. Furthermore, substantial evidence is now available from a number of plant species that shows differential gene expression of aquaporins in response to abiotic stresses such as salinity, drought, or cold and clearly establishes the aquaporins as major players in the response of plants to conditions that affect water availability. This review summarizes the function and regulation of these genes to develop a greater understanding of the response of plants to water insufficiency, and particularly, to identify tolerant genotypes of major crop species including wheat and rice and plants that are important in agroforestry. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The aquaporin gene family of the ectomycorrhizal fungus Laccaria bicolor: lessons for symbiotic functions

Soil humidity and bulk water transport are essential for nutrient mobilization. Ectomycorrhizal fungi, bridging soil and fine roots of woody plants, are capable of modulating both by being integrated into water movement driven by plant transpiration and the nocturnal hydraulic lift. Aquaporins are integral membrane proteins that function as gradient-driven water and/or solute channels. Seven aquaporins were identified in the genome of the ectomycorrhizal basidiomycete Laccaria bicolor and their role in fungal transfer processes was analyzed. Heterologous expression in Xenopus laevis oocytes revealed relevant water permeabilities for three aquaporins. In fungal mycelia, expression of the corresponding genes was high compared with other members of the gene family, indicating the significance of the respective proteins for plasma membrane water permeability. As growth temperature and ectomycorrhiza formation modified gene expression profiles of these water-conducting aquaporins, specific roles in those aspects of fungal physiology are suggested. Two aquaporins, which were highly expressed in ectomycorrhizas, conferred plasma membrane ammonia permeability in yeast. This indicates that these proteins are an integral part of ectomycorrhizal fungus-based plant nitrogen nutrition in symbiosis.     

Arbuscular mycorrhizal symbiosis and plant aquaporin expression

Almost all land plants have developed a symbiosis with arbuscular mycorrhizal fungi. Establishment of the association is accompanied by structural changes in the plant root. During arbuscule formation fungal hyphae penetrate the root apoplast and install highly specialized interfaces for solute transport between plant and fungus. The periarbuscular membrane which is part of the plant plasma membrane surrounding arbuscular structures was shown to harbour a high density of different transport systems. Among these also expression of aquaporins was described, which potentially can act as a low affinity transport system for ammonia or ammonium. The present study provides data for expression, localization and function of plant aquaporins in the periarbuscular membrane of mycorrhizal Medicago truncatula plants.     

Significance of plasmalemma aquaporins for water‐transport in Arabidopsis thaliana

The plant plasma membrane intrinsic protein, PIP1b, facilitates water transport. These features were characterized in Xenopus oocytes and it has asked whether aquaporins are relevant for water transport in plants. In order to elucidate this uncertainty Arabidopsis thaliana was transformed with an anti-sense construct targeted to the PIP1b gene. Molecular analysis revealed that the anti-sense lines have reduced steady-state levels of PIP1b and the highly homologous PIP1a mRNA. The cell membrane water permeability was analyzed by swelling of protoplasts, which had been transferred into hypotonic conditions. The results indicate that the reduced expression of the specific aquaporins decreases the cellular osmotic water permeability coefficient approximately three times. The morphology and development of the anti-sense lines resembles that of control plants, with the exception of the root system, which is five times as abundant as that of control plants. Xylem pressure measurement suggests that the increase of root mass compensates the reduced cellular water permeability in order to ensure a sufficient water supply to the plant. The results obtained by this study, therefore, clearly demonstrate that aquaporins are important for plant water transport.     

植物水通道蛋白生理功能的研究进展

自1992年第一个水通道蛋白AQP1被人们认识以来,从植物中分离得到了大量AQPs基因。AQPs在植物体内形成选择性运输水及一些小分子溶质和气体的膜通道,参与介导多个植物生长发育的生理活动,如细胞伸长、气孔运动、种子发育、开花繁殖和逆境胁迫等。就植物水通道蛋白的生理功能进行概述。     

Aquaporins and biological rhythm

Aquaporins are membrane-intrinsic proteins that facilitate membrane transport of water and small solutes or even gases. Aquaporin genes are found in almost all living organisms. In plants the proteins account for water uptake and transport as well as CO₂ availability for photosynthesis. These processes are subjected to diurnal or circadian regimes. Expression and even function of aquaporins also follows day - night rhythms. Significance of aquaporin function in chronobiology has been provided by recent publications, which are summarised here. Examples of the significance of aquaporins in processes related to chronobiology are given for root water transport and leaf movement in several plant species.