Aquaporins play a major role in plant water uptake at both optimal and environmentally stressed conditions. However, the functional specificity of aquaporins under cold remains obscure. To get a better insight to the role of aquaporins in cold acclimation and freezing tolerance, we took an integrated approach of physiology, transcript profiling and cell biology in Arabidopsis thaliana. Cold acclimation resulted in specific upregulation of PIP1;4 and PIP2;5 aquaporin (plasma membrane intrinsic proteins) expressions and immunoblotting analysis confirmed the increase in amount of PIP2;5 protein and total amount of PIPs during cold acclimation, suggesting that PIP2;5 plays a major role in tackling the cold milieu. Although single mutants of pip1;4 and pip2;5 or their double mutant showed no phenotypic changes in freezing tolerance, they were more sensitive in root elongation and cell survival response under freezing stress conditions compared with the wild type. Consistently, single mutation in either PIP1;4 or PIP2;5 altered the expression of a number of aquaporins both at transcriptional and translational levels. Collectively, our results suggest that aquaporin members including PIP1;4 and PIP2;5 function in concert to regulate cold acclimation and freezing tolerance responses.

中文翻译：

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质膜水通道蛋白PIP协同调节拟南芥中的冷驯化和抗冻能力。

在最佳和环境胁迫条件下，水通道蛋白在植物水分吸收中起主要作用。然而，水通道蛋白在寒冷下的功能特异性仍然不清楚。为了更好地了解水通道蛋白在冷驯化和抗冻性中的作用，我们采用了拟南芥中生理学，转录谱分析和细胞生物学的综合方法。冷驯化导致PIP1; 4和PIP2; 5水质蛋白（质膜内在蛋白）的表达上调，免疫印迹分析证实冷驯化期间PIP2; 5蛋白质的量和PIP总量增加，表明PIP2; 5发挥了作用在解决感冒环境方面发挥了重要作用。尽管pip1; 4和pip2; 5的单个突变体或它们的双重突变体在耐冻性方面没有表现出表型变化，与野生型相比，它们在冷冻胁迫条件下对根伸长和细胞存活反应更为敏感。一致地，PIP1; 4或PIP2; 5中的单个突变会在转录和翻译水平上改变许多水通道蛋白的表达。总体而言，我们的研究结果表明，包括PIP1; 4和PIP2; 5在内的水通道蛋白成员共同调节寒冷的适应性和抗冻性。