Instituto de Ingeniería Genética y Biología Molecular (INGEBI-CONICET), Vuelta de Obligado 2490 Piso 2, 1428 Buenos Aires, Argentina.
Plant J. 2010 Dec;64(6):1038-47. doi: 10.1111/j.1365-313X.2010.04395.x. Epub 2010 Nov 17.
In plant sexual reproduction, water and solute movement are tightly regulated, suggesting the involvement of aquaporins. We previously identified TIP5;1 and TIP1;3 as the only Arabidopsis aquaporin genes that are selectively and highly expressed in mature pollen, and showed that they can transport both water and urea when expressed in Xenopus oocytes. Here, we show that TIP5;1 has unusual characteristics, as its water transport activity is regulated by pH. Analysis of the water transport activity of a mutant version of TIP5;1 (TIP5;1-H131A) and amino acid alignment with other plant aquaporins regulated by pH suggested that a conserved motif is involved in pH sensing. GFP-TIP5;1 is located in the mitochondria of pollen tubes. The single mutants tip1;3 and tip5;1, as well as the tip1;3 tip5;1 double mutant, are fertile, but all mutants had shorter than normal pollen tubes when germinated in vitro in the absence of exogenous nitrogen. Thus, we propose that TIP5;1 and TIP1;3 are involved in nitrogen recycling in pollen tubes of Arabidopsis thaliana.
在植物有性生殖中，水和溶质的移动受到严格调控，这表明水通道蛋白（aquaporin）参与其中。我们之前鉴定出 TIP5;1 和 TIP1;3 是拟南芥中唯一在成熟花粉中特异且高度表达的水通道蛋白基因，并表明它们在非洲爪蟾卵母细胞中表达时既能运输水也能运输尿素。在这里，我们发现 TIP5;1 具有不寻常的特性，因为其水运输活性受 pH 值调控。对 TIP5;1 的突变体（TIP5;1-H131A）的水运输活性分析以及与其他受 pH 值调控的植物水通道蛋白的氨基酸序列比对表明，一个保守基序参与 pH 值感应。GFP-TIP5;1 定位于花粉管的线粒体中。单个突变体 tip1;3 和 tip5;1 以及 tip1;3 tip5;1 双突变体是可育的，但在体外无外源氮的情况下萌发时，所有突变体的花粉管都比正常的短。因此，我们提出 TIP5;1 和 TIP1;3 参与了拟南芥花粉管中的氮循环。
