AUTHOR=Jian Shaofen , Luo Jingsong , Liao Qiong , Liu Qiang , Guan Chunyun , Zhang Zhenhua TITLE=NRT1.1 Regulates Nitrate Allocation and Cadmium Tolerance in Arabidopsis JOURNAL=Frontiers in Plant Science VOLUME=10 YEAR=2019 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00384 DOI=10.3389/fpls.2019.00384 ISSN=1664-462X ABSTRACT=

Abiotic stress induces nitrate (NO₃^-) allocation to roots, which increases stress tolerance in plants. NRT1.1 is broadly involved in abiotic stress tolerance in plants, but the relationship between NRT1.1 and NO₃^- allocation under stress conditions is unclear. In this study, we found that Arabidopsis wild-type Col-0 was more cadmium (Cd²⁺)-tolerant than the nrt1.1 mutant at 20 μM CdCl₂. Cd²⁺ exposure repressed NRT1.5 but upregulated NRT1.8 in roots of Col-0 plants, resulting in increased NO₃^- allocation to roots and higher [NO₃^-] root-to-shoot (R:S) ratios. Interestingly, NITRATE REGULATORY GENE2 (NRG2) was upregulated by Cd²⁺ stress in Col-0 but not in nrt1.1. Under Cd²⁺ stress, nrg2 and nrg2-3chl1-13 mutants exhibited similar phenotypes and NO₃^- allocation patterns as observed in the nrt1.1 mutant, but overexpression of NRG2 in Col-0 and nrt1.1 increased the [NO₃^-] R:S ratio and restored Cd²⁺ stress tolerance. Our results indicated that NRT1.1 and NRG2 regulated Cd²⁺ stress-induced NO₃^- allocation to roots and that NRG2 functioned downstream of NRT1.1. Cd²⁺ uptake did not differ between Col-0 and nrt1.1, but Cd²⁺ allocation to roots was higher in Col-0 than in nrt1.1. Stressed Col-0 plants increased Cd²⁺ and NO₃^- allocation to root vacuoles, which reduced their cytosolic allocation and transport to the shoots. Our results suggest that NRT1.1 regulates NO₃^- allocation to roots by coordinating Cd²⁺ accumulation in root vacuoles, which facilitates Cd²⁺ detoxification.