Nitrate regulation of AFB3 and NAC4 gene expression in Arabidopsis roots depends on NRT1.1 nitrate transport function.

Nitrogen is an essential macronutrient for plants and its availability is a major limiting factor for plant growth and crop production. Nitrate is the main source of inorganic N for plants in aerobic soils and can act as a potent signal to control global gene expression. We found that gene expression in response to nitrate treatment of the AFB3 auxin receptor and its target, the NAC4 transcription factor depends on the nitrate transport function of NRT1.1. This gene regulatory function of NRT1.1 on AFB3 and NAC4 differs from the previously described signaling function controlling NRT2.1, NIA1 and NIA2 transcript levels and root colonization of nitrate-rich patches. Our work suggests two different signaling pathways may exist to control gene expression in response to nitrate downstream of NRT1.1.