Nitrogen supply enhances zinc uptake and root-to-shoot translocation via up-regulating the expression of TaZIP3 and TaZIP7 in winter wheat (Triticum aestivum)

Background and aims: Nitrogen (N) is critical for zinc (Zn) uptake into plant roots, which promotes Zn accumulation and biofortification of grains in winter wheat (Triticum aestivum L.). However, little is known about the role of TaZIPs genes in the Zn uptake and translocation in response to N supply. This study explored a possible avenue to improve Zn uptake and translocation by adjusting N supply in winter wheat. Methods: Winter wheat (Triticum aestivum.cv Zhengmai379) was cultivated with low, medium and high N in a nutrition solution or a pot soil with or without Zn supply. Plants in hydroponic culture were harvested at 21 d after different treatments and those in the soil culture were harvested at grain filling stage, and N and Zn concentrations and accumulation, Zn translocation coefficient, and the expression of TaZIP3 and TaZIP7 in different tissues were determined. Results: When N supply was increased, Zn concentration and accumulation in shoot, Zn accumulation in whole plants, and root-to-shoot translocation of Zn were decreased in the solution without Zn supply. In the solution with Zn supply, increasing N supply increased Zn concentration in shoot, and medium N supply increased Zn accumulation in shoot and whole plants. Increasing N supply increased Zn concentration and accumulation in root, stem, leaf, glume and grain, and Zn translocation form root to stem, but decreased Zn translocation from stem to leaf, stem to glume and glume to grain under both Zn-deficient and Zn-sufficient conditions. Medium N supply up-regulated the expression of TaZIP3 and TaZIP7 in the roots of winter wheat cultured under both Zn-deficient and Zn-sufficient conditions. In Zn-deficient soil, the expression of TaZIP3 and TaZIP7 in root and glume was up-regulated but that in stem and leaf was down-regulated by increasing N supply. Medium or high N supply induced the expression of TaZIP3 and TaZIP7 in different tissues of winter wheat grown under Zn-sufficient condition. Conclusions: Adequate N supply improves the grain Zn concentration through enhancing Zn uptake and root-to-shoot translocation, which could be mediated by induced expression of TaZIP3 and TaZIP7 in roots of winter wheat.