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.
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The data that support the findings of this study are available from the corresponding authors upon request.
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pCAMBIA1300–nLUC/cLUC vectors were kindly provided by J.-M. Zhou, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. The SPX4pro–gSPX4–GUS transgenic rice was kindly provided by C. Mao, College of Life Sciences, Zhejiang University. The authors thank T. O. Jobe (University of Cologne) for proofreading the manuscript. This work was supported by grants from the Chinese Academy of Sciences (XDA08010400), the National Natural Sciences Foundation of China (31500975 and 31771348) and the China Postdoctoral Science Foundation (2017M610126). Research in the laboratory of S. Kopriva was supported by Deutsche Forschungsgemeinschaft (EXC 1028).
The authors declare no competing interests.
Journal peer review information: Nature Plants thanks Dong Liu, Nicholaus von Wiren, Ying Liu, Ricardo Giehl and other anonymous reviewers for their contribution to the peer review of this work.
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Hu, B., Jiang, Z., Wang, W. et al. Nitrate–NRT1.1B–SPX4 cascade integrates nitrogen and phosphorus signalling networks in plants. Nat. Plants 5, 401–413 (2019). https://doi.org/10.1038/s41477-019-0384-1