Arabidopsis NRT1.5 Is Another Essential Component in the Regulation of Nitrate Reallocation and Stress Tolerance  

Abstract

Nitrate reallocation to plant roots occurs frequently under adverse conditions and was recently characterized to be actively regulated by Nitrate Transporter1.8 (NRT1.8) in Arabidopsis (Arabidopsis thaliana) and implicated as a common response to stresses. However, the underlying mechanisms remain largely to be determined. In this study, characterization of NRT1.5, a xylem nitrate-loading transporter, showed that the mRNA level of NRT1.5 is down-regulated by salt, drought, and cadmium treatments. Functional disruption of NRT1.5 enhanced tolerance to salt, drought, and cadmium stresses. Further analyses showed that nitrate, as well as Na + and Cd 2+ levels, were significantly increased in nrt1.5 roots. Important genes including Na + /H + exchanger1, Salt overly sensitive1, Pyrroline-5-carboxylate synthase1, Responsive to desiccation29A, Phytochelatin synthase1, and NRT1.8 in stress response pathways are steadily up-regulated in nrt1.5 mutant plants. Interestingly, altered accumulation of metabolites, including proline and malondialdehyde, was also observed in nrt1.5 plants. These data suggest that NRT1.5 is involved in nitrate allocation to roots and the consequent tolerance to several stresses, in a mechanism probably shared with NRT1.8.

Nitrogen Use Efficiency Is Mediated by Vacuolar Nitrate Sequestration Capacity in Roots of Brassica napus

“…Expression of the two genes is influenced by NO 3 2 concentration. NRT1.5 is strongly induced by NO 3 2 (Lin et al, 2008), while NRT1.8 expression is extremely up-regulated in nrt1.5 mutants (Chen et al, 2012). A negative correlation between the extents of expression of the two genes was observed when plants are subjected to abiotic stresses (Chen et al, 2012).…”

“…A previous study showed that increased NRT1.8 expression in nrt1.5 mutants (Chen et al, 2012) and the expression of NRT1.5 was induced by NO 3 2 (Lin et al, 2008). We tested the relationship between NRT1.5 and NRT1.8 expression in Arabidopsis and B. napus.…”

“…3; Chen et al, 2012). We then hypothesized that expression of these two genes is contrastingly regulated by concentration of NO 3 2 in the cytosol.…”

“…A previous study showed that expression of NRT1.5 is down-regulated by ACC and MeJA treatments, while the expression of NRT1.8 is strongly upregulated in Arabidopsis . Consequently, NO 3 2 accumulated in plant roots, probably as an adaptive measure for abiotic stresses (Chen et al, 2012). Both the H-and L-B.…”

“…NRT1.5 is strongly induced by NO 3 2 (Lin et al, 2008), while NRT1.8 expression is extremely up-regulated in nrt1.5 mutants (Chen et al, 2012). A negative correlation between the extents of expression of the two genes was observed when plants are subjected to abiotic stresses (Chen et al, 2012). Moreover, expression of NRT1.5 is strongly inhibited by 1-aminocyclopropane-1-carboxylic acid (ACC) and methyl jasmonate (MeJA), whereas the expression of NRT1.8 is significantly up-regulated .…”