Characterization of nitrogen transporters in maize brace roots

Abstract

Nitrogen is an essential macronutrient for plant growth and development and typically the most limiting nutrient in most environments. As a result, it is commonly applied to agricultural fields in large amounts to support crop productivity. To optimize nitrogen fertilization rates, it is essential to have a clear understanding of how plants interact with nitrogen. While advances in molecular methods have improved our understanding of plant-nitrogen relations, many aspects of nitrogen uptake remain to be elucidated, even in major crop species such as maize. This work will review existing methods used to study nitrogen uptake and characterize nitrogen uptake via transporters in maize through two studies. In the first, nitrogen uptake assays were conducted on aerial and soil brace roots of five maize genotypes. These assays revealed that aerial brace roots take up more nitrogen than soil brace roots. Further analysis identified ZmNPF3.2, ZmNPF5.16, and ZmNPF6.2 as candidate genes contributing to the enhanced nitrogen uptake in aerial brace roots. The second study used maize plants with mutations in previously uncharacterized ammonium transporters (ZmAMF1.1, ZmAMF1.2, ZmAMT2.1, and ZmAMT3.2) to investigate their contribution to ammonium uptake and translocation in maize plants. Mutant plants showed phenotypic differences in the field that suggested impaired nitrogen translocation, but minimal differences in short-term nitrogen uptake in brace roots compared to wildtype plants. Further analysis via long-term uptake experiments determined that ZmAMT2.1 mutants demonstrated abnormal nitrogen distribution patterns. This research contributes to a growing foundational knowledge of nitrogen uptake and transport in maize plants, ultimately leading to crops optimized for nitrogen uptake and improved agricultural practices.