Kotur Zorica, Glass Anthony D M
Department of Botany, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia, V6T 1Z4, Canada.
Plant Cell Environ. 2015 Aug;38(8):1490-502. doi: 10.1111/pce.12496. Epub 2015 Jan 31.
In plants that have been deprived of nitrate for a significant length of time, a constitutive high-affinity nitrate transport system (cHATS) is responsible for initial nitrate uptake. This absorbed nitrate leads to the induction of the major nitrate transporters and enzymes involved in nitrate assimilation. By use of (13) NO3 (-) influx measurements and Blue Native polyacrylamide gel electrophoresis we examined the role of AtNRT2.5 in cHATS in wild type (WT) and various T-DNA mutants of Arabidopsis thaliana. We demonstrate that AtNRT2.5 is predominantly expressed in roots of nitrate-deprived WT plants as a 150 kDa molecular complex with AtNAR2.1. This complex represents the major contributor to cHATS influx, which is reduced by 63% compared with WT in roots of Atnrt2.5 mutants. The remaining cHATS nitrate influx in these mutants is due to a residual contribution by the inducible high-affinity transporter encoded by AtNRT2.1/AtNAR2.1. Estimates of the kinetic properties of the NRT2.5 transporter reveal that its low Km for nitrate makes this transporter ideally suited to detect and respond to trace quantities of nitrate in the root environment.
在长时间缺乏硝酸盐的植物中，组成型高亲和力硝酸盐转运系统（cHATS）负责最初的硝酸盐吸收。这种吸收的硝酸盐会诱导参与硝酸盐同化的主要硝酸盐转运蛋白和酶。通过使用（13）NO3（-）流入测量和蓝色天然聚丙烯酰胺凝胶电泳，我们研究了拟南芥野生型（WT）和各种T-DNA突变体中AtNRT2.5在cHATS中的作用。我们证明，AtNRT2.5在缺乏硝酸盐的WT植物根中主要作为与AtNAR2.1形成的150 kDa分子复合物表达。该复合物是cHATS流入的主要贡献者，与Atnrt2.5突变体根中的WT相比，其减少了63%。这些突变体中剩余的cHATS硝酸盐流入是由于AtNRT2.1/AtNAR2.1编码的可诱导高亲和力转运蛋白的残余贡献。对NRT2.5转运蛋白动力学特性的估计表明，其对硝酸盐的低Km值使该转运蛋白非常适合检测和响应根环境中的微量硝酸盐。
