Localization and quantification of plasma membrane aquaporin expression in maize primary root: A clue to understanding their role as cellular plumbers
Localization and quantification of plasma membrane aquaporin expression in maize primary root: A clue to understanding their role as cellular plumbers
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DOI：
10.1007/s11103-006-9022-1
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发表时间：
2006-09-01
影响因子：
5.1
通讯作者：
Chaumont, Francois
中科院分区：
文献类型：
--
作者：
Hachez, Charles;Moshelion, Menachem;Chaumont, Francois
水分跨根组织的运输是通过平行的质外体、共生体和跨细胞途径进行的，植物在一定程度上可以控制这些途径。由于水通道或水通道蛋白(AQP)在调节水分流动中起着重要作用，因此研究AQP在不同根组织中的表达具有重要意义。在这里，我们利用原位和定量RT-PCR和免疫检测方法对玉米质膜AQP(ZmPIPs)在初生根尖中的表达进行了定量和定位。除ZmPIP2；7外，其余ZmPIP基因均在初生根中表达。研究发现，根的表达取决于根的发育阶段，一般情况下，向伸长和成熟区表达增加。ZmPIP1；5和ZmPIP2；5两个基因在成熟区的表达增加最多(分别高达11倍和17倍)，占ZmPIPs总表达的50%。ZmPIP2；1和ZmPIP2；5在外胚层和内胚层的免疫细胞化学定位表明，它们参与了根的径向水分运动。此外，我们还检测到ZmPIP2；5在根尖表皮细胞的外周侧极性定位，这表明ZmPIP2；5在根表面的水分吸收中起着重要作用。最后，原生质体膨胀分析表明，根细胞表现出一个可变的、但总体上较低的渗透系数(P(F)<；10mum/S)。然而，在根的成熟区出现高P(F)(高达26微米/S)的细胞群体可能与几个ZmPIP基因的表达增加有关。
Water movement across root tissues occurs by parallel apoplastic, symplastic, and transcellular pathways that the plant can control to a certain extent. Because water channels or aquaporins (AQPs) play an important role in regulating water flow, studies on AQP mRNA and protein expression in different root tissues are essential. Here, we quantified and localized the expression of Zea mays plasma membrane AQPs (ZmPIPs) in primary root tip using in situ and quantitative RT-PCR and immunodetection approaches. All ZmPIP genes except ZmPIP2;7 were expressed in primary roots. Expression was found to be dependent on the developmental stage of the root, with, in general, an increase in expression towards the elongation and mature zones. Two genes, ZmPIP1;5 and ZmPIP2;5, showed the greatest increase in expression (up to 11- and 17-fold, respectively) in the mature zone, where they accounted for 50% of the total expressed ZmPIPs. The immunocytochemical localization of ZmPIP2;1 and ZmPIP2;5 in the exodermis and endodermis indicated that they are involved in root radial water movement. In addition, we detected a polar localization of ZmPIP2;5 to the external periclinal side of epidermal cells in root apices, suggesting an important role in water uptake from the root surface. Finally, protoplast swelling assays showed that root cells display a variable, but globally low, osmotic water permeability coefficient (P (f) < 10 mu m/s). However, the presence of a population of cells with a higher P (f) (up to 26 mu m/s) in mature zone of the root might be correlated with the increased expression of several ZmPIP genes.