Nitrogen (N) is a macronutrient that plays a crucial role in plant growth and development. Nitrate (NO−3) is the most abundant N source in aerobic soils. Plants have evolved two adaptive mechanisms such as up-regulation of the high-affinity transport system (HATS) and alteration of the root system architecture (RSA), allowing them to cope with the temporal and spatial variation of NO−3. However, little information is available regarding the nitrate transporter in cucumber, one of the most important fruit vegetables in the world. In this study we isolated a nitrate transporter named CsNRT2.1 from cucumber. Analysis of the expression profile of the CsNRT2.1 showed that CsNRT2.1 is a high affinity nitrate transporter which mainly located in mature roots. Subcellular localization analysis revealed that CsNRT2.1 is a plasma membrane transporter. In N-starved CsNRT2.1 knock-down plants, both of the constitutive HATS (cHATS) and inducible HATS (iHATS) were impaired under low external NO−3 concentration. Furthermore, the CsNRT2.1 knock-down plants showed reduced root length and lateral root numbers. Together, our results demonstrated that CsNRT2.1 played a dual role in regulating the HATS and RSA to acquire NO−3 effectively under N limitation.
Li, Y., Li, J., Yan, Y., Liu, W., Zhang, W., Gao, L., & Tian, Y. (2018). Knock-down of csNRT2.1, a cucumber nitrate transporter, reduces nitrate uptake, root length, and lateral root number at low external nitrate concentration. Frontiers in Plant Science, 9. https://doi.org/10.3389/fpls.2018.00722