Nitrogen is a major limiting factor for crop productivity. For most plants, nitrate is their primary nitrogen source. Nitrate taken into the plant can be assimilated right away in the root tissue, stored in the vacuole for future use, or transported to the leaf tissue and assimilated there. Characterization of nitrate transporter genes in the NRT1 (PTR) family revealed novel molecular and regulatory mechanisms for several critical steps of nitrate transport including uptake, storage, xylem loading and unloading, and remobilization.
Nitrate also serves as a signaling molecule regulating plant growth and flowering. Dual-affinity nitrate transporter CHL1 is switched between high- and low-affinity modes of transport by phosphorylation and dephosphorylation at threonine residue 101. In addition to being a transporter, CHL1 also functions as a nitrate sensor, named as transceptor. By dual-affinity binding, phosphorylation switches as well as the dynamic interactions with two kinases and one phosphatase, CHL1 can sense wide range of nitrate concentration changes in the soil, and induce different levels of transcriptional responses. This mechanism becomes a paradigm for how other nutrients are sensed. NRT1.13 is another transceptor in the NRT1 family. Study of NRT1.13 tell us how internal nitrate is sensed to regulate shoot architecture and flowering time. We are taking genetics, cell biology and biophysics approaches to understand how cell-to-cell communication and dynamic protein-to-protein interaction are involved in the concentration- and temporal-dependent responses.
Nitrogen is a major limiting factor for crop productivity. Production of N fertilizer consumes 1-2% of global energy. Nevertheless, only 30-50% of N fertilizer applied is utilized by crops, and the reminder leads to severe environmental problems. Therefore, enhancing crop NUE is an urgent issue for sustainable agriculture. Several NRT1 genes provide new tools of engineering crops to enhance NUE. In addition, GWAS approach will be taken to systematically identify new genes for improving NUE.
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