Gene

Cell biology

Biology

Ubiquitin ligase

Biochemistry

Nitrogen

Ubiquitin

Phosphate

Organic chemistry

Oryza sativa

Transcription factor

Chemistry

Nitrate

Nature Plants

To ensure high crop yields in a sustainable manner, a comprehensive understanding of the control of nutrient acquisition is required. In particular, the signalling networks controlling the coordinated utilization of the two most highly demanded mineral nutrients, nitrogen and phosphorus, are of utmost importance. Here, we reveal a mechanism by which nitrate activates both phosphate and nitrate utilization in rice (Oryza sativa L.). We show that the nitrate sensor NRT1.1B interacts with a phosphate signalling repressor SPX4. Nitrate perception strengthens the NRT1.1B–SPX4 interaction and promotes the ubiquitination and degradation of SPX4 by recruiting NRT1.1B interacting protein 1 (NBIP1), an E3 ubiquitin ligase. This in turn allows the key transcription factor of phosphate signalling, PHR2, to translocate to the nucleus and initiate the transcription of phosphorus utilization genes. Interestingly, the central transcription factor of nitrate signalling, NLP3, is also under the control of SPX4. Thus, nitrate-triggered degradation of SPX4 activates both phosphate- and nitrate-responsive genes, implementing the coordinated utilization of nitrogen and phosphorus. In rice, nitrate perception by NRT1.1B activates genetic responses that increase the utilization of not only nitrate but also phosphate. A novel molecular mechanism centred on the presumed Pi sensor SPX4 underlies this nutritional signalling crosstalk.

Nitrate–NRT1.1B–SPX4 cascade integrates nitrogen and phosphorus signalling networks in plants