Zn promoted translocation and distribution of N into leaves and brown rice.
Zn induced the expression levels of N transporter genes in both root and shoot.
Zn increased the N assimilation level in leaves.
N promoted translocation and distribution of Zn into leaves and brown rice.
N up-regulated the expression levels of Zn transporter genes in both root and shoot.
Multiple studies have shown strong relationships between different nutrients in plants, and the important role of N in Zn acquisition and translocation has been recognized.
The aim of this study was to estimate the effect of Zn on N uptake, translocation, and distribution in rice as well as the corresponding molecular mechanisms. We also aimed to evaluate the impact of N on the Zn content in rice grains which is closely related to the Zn nutrition in humans with rice-based diets.
We conducted both field trials and hydroponic cultures of two rice cultivars to analyze the growth and yield, the uptake, translocation, and distribution of N and Zn, as well as the expression of N transport and assimilation genes, and the Zn transporter genes under different combined applications of N and Zn.
Zn supply promoted the root-to-shoot translocation (12–70% increasing) and distribution of N into the leaves (19–49% increasing) and brown rice (6–9% increasing) and increased the rice biomass (by 14–35%) and yield (by 13–63%). Zn supply induced the expression of OsNRTs and OsAMTs in both roots and shoots, but repressed the expression of OsNiR2, OsGS1;2, and OsFd-GOGAT in roots, whereas it activated the expression of OsNiR2, OsGS1;1, OsGS2, and OsFd-GOGAT in the shoots. Moreover, the enzyme activities of nitrite reductase, nitrate reductase, and glutamine synthetase increased and the free NO 3 – concentration decreased, but the soluble protein concentration increased significantly in the shoots after Zn supply. Synergistically, N significantly facilitated the root-to-shoot translocation (1.68–11.66 fold) and distribution of Zn into the leaves (1.68–6.37 fold) and brown rice (7–12% increasing) and upregulated the expression levels of Zn transporter genes in both the roots and shoots.