Abstract
Phosphorus and nitrogen are essential macronutrients for plant growth and crop production. During phosphate (Pi) starvation, plants enhanced Pi but reduced nitrate (NO(3) (-)) uptake capacity, and the mechanism is unclear. Here, we show that a GARP-type transcription factor NITRATE-INDUCIBLE, GARP-TYPE TRANSCRIPTIOANL REPRESSOR1.2 (NIGT1.2) coordinately modulates Pi and NO(3) (-) uptake in response to Pi starvation. Overexpression of NIGT1.2 increased Pi uptake capacity but decreased NO(3) (-) uptake capacity in Arabidopsis (Arabidopsis thaliana). Furthermore, the nigt1.1 nigt1.2 double mutant displayed reduced Pi uptake but enhanced NO(3) (-) uptake under low-Pi stress. During Pi starvation, NIGT1.2 directly up-regulated the transcription of the Pi transporter genes PHOSPHATE TRANSPORTER1;1 (PHT1;1) and PHOSPHATE TRANSPORTER1;4 (PHT1;4) and down-regulated expression of NO(3) (-) transporter gene NITRATE TRANSPORTER1.1 (NRT1.1) by binding to cis-elements in their promoters. Further genetic assays demonstrated that PHT1;1, PHT1;4, and NRT1.1 were genetically epistatic to NIGT1.2 We also identified similar regulatory pathway in maize (Zea mays). These data demonstrate that the transcription factor NIGT1.2 plays a central role in modulating low-Pi-dependent uptake of Pi and NO(3) (-), tending toward maintenance of the phosphorus to nitrogen balance in plants during Pi starvation.