A Transcription Factor, OsMADS57, Regulates Long-Distance Nitrate Transport and Root Elongation (Plant Phys.)

Nitrogen is a critical macronutrient for plant growth and reproduction, and it’s largely present as ammonium in flooded and acidic soils. However, structurally porous tissue in rice roots, called aerenchyma, transfer oxygen to the root system in flooded paddies, increasing nitrate abundance. Huang et al. used a transcription factor, OsMADS57, to study the complex regulation of nitrogen homeostasis in a hydroponic setting. The group used mutants and overexpressing rice lines of OsMADS57, along with nitrogen isotope labeling to demonstrate that MADS57 regulates the root to shoot transport of nitrate. This was confirmed through RT-qPCR analysis, which showed a MADS57 transcriptional effect on members of the OsNRT2 family and nitrate reductase. Furthermore, a yeast 1-hybrid assay and transient tobacco expression revealed that MADS57 binds a specific CArG box in the promoter of NRT2.3a. Lastly, OsMADS57 was shown to alter auxin accumulation and growth of seminal rice roots. Taken together, these results highlight an additional regulator of nitrogen homeostasis and root growth in rice. (Summary by Nathan Scinto-Madonich) Plant Phys. 10.1104/pp.19.00142