Balancing phosphorus and nitrogen during phosphate starvation

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Wang et al. explore how plants increase Pi uptake and reduce nitrate uptake during Pi starvation.

Plant Cell https://doi.org/10.1105/tpc.20.00361

By Xue Wang and Yi-Fang Chen

State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Center for Crop Functional Genomics and

Molecular Breeding, Beijing, China

Background: Phosphorus (P) and nitrogen (N) are essential for all plants, and are often the elements that limit primary productivity. P mobility in soil is limited. Whereas soil concentrations of inorganic P, mainly in the form of orthophosphate (PO43−; Pi), are low, those of organic P tend to be higher. As organic P cannot be absorbed by plants, the low Pi concentration in the soil results in low Pi availability for plant growth and survival. Nitrate in aerobic soils is a major N source for plants. During Pi starvation, plants enhance Pi uptake but reduce nitrate uptake; however, the underlying mechanism is unclear.

Question: What is the molecular mechanism by which plants modulate phosphate and nitrate uptake under Pi-deficient conditions?

Findings: We showed that under Pi-deficient and nitrate-sufficient conditions, the Arabidopsis thaliana transcription factors NIGT1.1 and NIGT1.2 had a dual role both as direct activators of Pi transporters and as direct repressors of nitrate transporters, and thereby balanced N and P uptake. A similar regulatory pathway was identified in maize.

Next steps: We established that NIGT1.1/1.2 modulates nitrate and phosphate uptake in response to the combined availability of P and N. Under various P/N combinations, NIGT1.1/1.2 may be modulated at both the transcriptional and posttranscriptional levels. We plan to investigate the mechanisms that regulate NIGT1 proteins under various P/N supply conditions.

Xue Wang, Hai-Feng Wang, Yun Chena, Mi-Mi Sun, Yi Wanga, and Yi-Fang Chen. (2020). The Transcription Factor NIGT1.2 Modulates Both Phosphate Uptake and Nitrate Influx during Phosphate Starvation in Arabidopsis and Maize. Plant Cell; DOI: https://doi.org/10.1105/tpc.20.00361