Research
Nitrate Transport and Sensing in Higher Plants
I. Functional genomic analysis of NRT1 (PTR) genes in Arabidopsis
Under a lot of conditions, nitrogen is the 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.
Through the analyses of nitrate transporter genes in the NRT1 (PTR) family, we have elucidated the molecular and regulatory mechanisms of several critical steps of nitrate transport including nitrate uptake, nitrate storage, nitrate xylem loading and unloading, and nitrate remobilization.
Arabidopsis genome contains 53 NRT1 (PTR) genes, 10 fold more than the PTR genes found in animal, suggesting that NRT1 (PTR) genes play some unique and critical roles in higher plants. Some members of NRT1 (PTR) genes encode di-peptide transporters. To find out the novel substrate of NRT1(PTR) transporters, Taking reverse genetic approach was taken. And, we found that some NRT1(PTR) members can transport glutathione and is involved in cadmium tolerance.
II. Nitrate sensing
Although nitrate is a critical signaling molecule in regulating plant growth, little is know about plant nitrate signaling at molecular level. CHL1, a dual-affinity nitrate transporter, is switched between high- and low-affinity modes by phosphorylation and dephosphorylation: When CHL1 is phosphorylated at threonine residue 101, it functions as a high-affinity transporter; when dephosphorylated, it functions as low-affinity nitrate transporter. Our recent data suggested that CHL1 also function as a nitrate sensor, and high- and low-affinity sensing is regulated by CIPK23.
