Nickel plays an important physiological role in plants, but how it is transported over long distances from stems and leaves to grains was poorly understood for more than 50 years.
Now researchers have identified a key transporter gene, ZmNAET1 , that controls nickel accumulation in cereal grains.
They also uncovered how nicotianamine (NA), a plant-specific non-protein amino acid, mediates the long-distance transport of nickel and established the crucial role of nickel-dependent urease activity in amino acid metabolism, seed vigor, and yield formation.
The study, published in Cell on November 11, was led by CHAO Daiyin at the Center for Excellence in Molecular Plant Sciences of the Chinese Academy of Sciences, in collaboration with YAN Jianbing’s team at Huazhong Agricultural University.
In 1840, Justus von Liebig, a founding figure in plant nutrition, proposed the “law of the minimum,” which states that crop growth is determined by the nutrient in shortest supply. According to this principle, crop yield may be determined not only by macronutrients such as nitrogen, phosphorus, and potassium, but also by micronutrients such as nickel.
In this study, the researchers identified ZmNAET1 through a genome-wide association study using data collected from 1,404 maize accessions across multiple years and locations.
They found that natural variation in the regulatory region of ZmNAET1 affects grain nickel content. Accessions with higher ZmNAET1 expression had approximately 60% higher grain nickel concentrations in their grains, indicating that natural variation at this locus could be exploited in breeding.
Further molecular, cell biological, and biochemical studies showed that ZmNAET1 serves as a crucial export component in the nickel transport pathway. It is localized primarily in phloem cells in stem nodes and ear shanks, where it exports NA synthesized within these cells. Outside the cells, NA binds free nickel to form Ni–NA complexes, which are then imported back into the phloem by other transporters and transported to sink organs such as grains.
Genetic analyses showed that ZmNAET1 controls not only grain nickel content in maize but also ear weight, grain size, starch content, and germination rates after storage by influencing nickel transport. When the gene’s function was impaired, grain nickel content declined substantially, accompanied by reductions in ear weight, grain size, starch content, and germination rates after storage. Mutant seeds stored for eight months to one year showed markedly reduced germination rates.
Nickel supplementation restored germination, whereas zinc supplementation did not. Foliar nickel application in the field also restored plant height and urease activity, both of which were reduced by impaired gene function.
The researchers also found that disrupted nickel transport decreased urease activity in sink organs such as grains, impairing urea utilization and, in turn, affecting amino acid synthesis and energy metabolism. These findings demonstrate that nickel transport links nitrogen metabolism with yield formation and seed vigor.
A Conserved Mechanism Across Cereal Crops
The researchers also extended their investigation by identifying two homologous genes, OsNAET1 and OsNAET2 , in rice. They found that these genes are key determinants of grain nickel content, indicating that this mechanism is conserved in cereal crops.
Whereas related genes in the model plant Arabidopsis thaliana primarily regulate iron, copper, and cobalt transport, NAET1 in maize and rice mainly affects the distribution of nickel and, to a lesser extent, zinc. This finding reflects differences in long-distance metal transport strategies between grasses and dicotyledonous plants.
Grasses have long been considered to have low nickel requirements and to rarely show signs of nickel deficiency. According to the researchers, this study is the first to identify genes controlling long-distance nickel transport in grasses. It reveals a previously unrecognized role of NA in mediating nickel allocation to sink organs as part of a process independent of the known mugineic acid pathway.
It fills a longstanding gap in our understanding of source-to-sink nickel transport and calls for a reassessment of the conventional view that grasses require little nickel and rarely experience nickel deficiency. The study also opens new avenues for improving cereal crop yield and seed vigor through nutrient management and molecular breeding, the researchers said.
Cell
Nicotianamine-driven Nickel Transport to Sink Organs Underpins Maize Productivity
10-Nov-2026