NIN-like protein 7 transcription factor is a plant nitrate sensor

Abstract

Nitrate is an essential nutrient and signaling molecule for plant growth. Plants sense intracellular nitrate to adjust their metabolic and growth responses. Here we identify the primary nitrate sensor in plants. We found that mutation of all seven Arabidopsis NIN-like protein (NLP) transcription factors abolished plants’ primary nitrate responses and developmental programs. Analyses of NIN-NLP7 chimeras and nitrate binding revealed that NLP7 is derepressed upon nitrate perception via its amino terminus. A genetically encoded fluorescent split biosensor, mCitrine-NLP7, enabled visualization of single-cell nitrate dynamics in planta. The nitrate sensor domain of NLP7 resembles the bacterial nitrate sensor NreA. Substitutions of conserved residues in the ligand-binding pocket impaired the ability of nitrate-triggered NLP7 to control transcription, transport, metabolism, development, and biomass. We propose that NLP7 represents a nitrate sensor in land plants.

Transcription-activating nitrate sensor

Plants depend on nitrogen, responding with changes in growth and metabolism when nitrogen supplies change. Indeed, nitrogen fertilizer underlies a good deal of agricultural crop productivity. Studying a family of seven similar genes, Liu et al . identified the nitrate sensor in the small mustard plant Arabidopsis thaliana . The protein’s nitrate-binding pocket resembles that found in bacteria nitrate sensors. Conformation change upon nitrate binding allows the protein to then function as a transcriptional activator, triggering the plant’s responses to nitrogen availability. —PJH

Abstract

A single bifunctional protein links nitrate sensing to changes in transcription in the small mustard plant Arabidopsis thaliana .