提出问题：During phosphate (Pi) starvation, plants enhanced Pi but reduced nitrate (NO3-) uptake capacity, and the mechanism is unclear.

主要发现：Here, we show that a GARP-type transcription factor NITRATE-INDUCIBLE, GARP-TYPE TRANSCRIPTIOANL REPRESSOR1.2 (NIGT1.2) coordinately modulates Pi and NO3- uptake in response to Pi starvation.

结果1-NIGT1.2过表达：Overexpression of NIGT1.2 increased Pi uptake capacity but decreased NO3- uptake capacity in Arabidopsis thaliana.

结果2-双突：Furthermore, the nigt1.1 nigt1.2 double mutant displayed reduced Pi uptake, but enhanced NO3- uptake under low-Pi stress.

结果3-作用机理：During Pi starvation, NIGT1.2 directly up-regulated the transcription of the Pi transporter genes PHOSPHATE TRANSPORTER 1;1(PHT1;1) and PHOSPHATE TRANSPORTER 1;4 (PHT1;4), and down-regulated expression of NO3- transporter gene NITRATE TRANSPORTER 1.1 (NRT1.1), by binding to cis-element in their promoters.

结果4-上位性：Further genetic assays demonstrated that PHT1;1, PHT1;4, and NRT1.1 were genetically epistatic to NIGT1.2.

结果5-玉米：We also identified similar regulatory pathway in maize (Zea mays).

结论：These data demonstrate that the transcription factor NIGT1.2 plays a central role in modulating low-Pi-dependent uptake of Pi and NO3-, tending towards maintenance of the phosphorus to nitrogen balance in plants during Pi starvation.

 摘  要 

磷和氮对于植物生长和作物产量都是必需的大量营养元素。在磷饥饿过程中，植物会增强Pi的吸收能力，而减少硝酸盐NO3-的吸收能力，但具体的机制并不清楚。本文中，作者发现GARP型转录因子NIGT1.2响应于Pi饥饿，协调调控Pi和NO3-的吸收。拟南芥NIGT1.2过表达能够增强Pi的吸收能力，但降低NO3-的吸收能力。此外，nigt1.1 nigt1.2双突植株再低Pi胁迫下，对Pi的吸收能力下降，但是对NO3-的吸收能力增强。在Pi饥饿时，NIGT1.2能够通过结合靶基因启动子区的顺式元件，直接上调Pi转运基因PHT1;1和PHT1;4的转录，并下调NO3-转运基因NRT1.1的表达。进一步的遗传实验显示PHT1;1、PHT1;4和NRT1.1对于NIGT1.2具有遗传上位性。作者在玉米中也有类似的发现。本文的研究揭示了转录因子NIGT1.2在低磷条件下Pi和NO3-的吸收过程中发挥至关重要的作用，在磷饥饿过程中趋向于维持磷（而非氮）的平衡。