Role of a single aquaporin isoform in root water uptake
Role of a single aquaporin isoform in root water uptake
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DOI：
10.1105/tpc.008888
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发表时间：
2003-02-01
期刊：
影响因子：
11.6
通讯作者：
Maurel, C
中科院分区：
文献类型：
--
作者：
Javot, H;Lauvergeat, V;Maurel, C
水通道蛋白是一种普遍存在的通道蛋白，其促进水穿过细胞膜的运输。水通道蛋白在植物中表现出典型的高亚型多样性，在拟南芥中有35个同源物。植物水通道蛋白的整体功能和每个单独的异构体的功能仍然知之甚少。基质辅助激光解吸/电离飞行时间分析表明，质膜内在蛋白2;2（PIP 2;2）是拟南芥根质膜中大量表达的水通道蛋白亚型之一。利用PCR技术从根癌农杆菌T-DNA插入诱变的植物株系文库中分离到两个独立的拟南芥PIP 2;2基因敲除突变体。PIP 2;2启动子-β-葡萄糖醛酸酶基因融合体在转基因拟南芥中的表达表明，PIP 2;2主要在根中表达，在皮层、内皮和中柱中有强表达。根皮层细胞的导水率，用细胞压力探针测量，减少了25至30%，在两个等位基因PIP 2;2突变体相比，野生型。此外，自由分泌测量结果显示，相对于野生型值，在两个PIP 2;2突变体切除的根的渗透导水率下降了14%。总之，我们的数据提供了证据，一个单一的水通道蛋白基因的贡献，根水分吸收和确定PIP 2;2作为一个水通道蛋白专门在渗透流体运输。PIP 2;2具有接近的同源物PIP 2;3，显示96.8%的氨基酸同一性。PIP 2的表型; 2突变体表明，尽管它们的高度同源性和异构体的多样性，植物水通道蛋白已经进化与非冗余功能。
Aquaporins are ubiquitous channel proteins that facilitate the transport of water across cell membranes. Aquaporins show a typically high isoform multiplicity in plants, with 35 homologs in Arabidopsis. The integrated function of plant aquaporins and the function of each individual isoform remain poorly understood. Matrix-assisted laser desorption/ionization time-of-flight analyses suggested that Plasma Membrane Intrinsic Protein2;2 (PIP2;2) is one of the abundantly expressed aquaporin isoforms in Arabidopsis root plasma membranes. Two independent Arabidopsis knockout mutants of PIP2;2 were isolated using a PCR-based strategy from a library of plant lines mutagenized by the insertion of Agrobacterium tumefaciens T-DNA. Expression in transgenic Arabidopsis of a PIP2;2 promoter-beta-glucuronidase gene fusion indicated that PIP2;2 is expressed predominantly in roots, with a strong expression in the cortex, endodermis, and stele. The hydraulic conductivity of root cortex cells, as measured with a cell pressure probe, was reduced by 25 to 30% in the two allelic PIP2;2 mutants compared with the wild type. In addition, free exudation measurements revealed a 14% decrease, with respect to wild-type values, in the osmotic hydraulic conductivity of roots excised from the two PIP2;2 mutants. Together, our data provide evidence for the contribution of a single aquaporin gene to root water uptake and identify PIP2;2 as an aquaporin specialized in osmotic fluid transport. PIP2;2 has a close homolog, PIP2;3, showing 96.8% amino acid identity. The phenotype of PIP2;2 mutants demonstrates that, despite their high homology and isoform multiplicity, plant aquaporins have evolved with nonredundant functions.