植物的根是通过根尖的分生组织活动来维持的。根分生组织发育过程中有两条转录途径，一条由PULTORAS(PLTS)介导，另一条由SHORTROOT(SHR)和稻草人(SCR)介导。PLT在根分生组织发育过程中的作用需要一个浓度梯度，这不仅是由生长稀释和细胞间运动等翻译后调控所致，也可能是由一种很大程度上未知的微调转录调控机制造成的。我们在这里报道了拟南芥通过招募RNA聚合酶II(POL II)到PLT1并与PLT1相互作用来正向调节PLT1在根分生组织中的表达。GRF相互作用因子1/ANGUSTIFOLIA3(GIF1/AN3)通过竞争结合Janus来抑制Pol II的Janus依赖的招募，GIF1/AN3是一种负调控PLT1表达的转录辅助因子。最后，plt1的拮抗调节因子Gif1和JANUS都依赖于拟南芥Importinβ4(IMB4)的核积累。在PLT1转录中，导入蛋白与其两个拮抗因子的结合可能对微调PLT1在根分生组织中的转录具有重要意义。

Plant roots are sustained through meristem activity at the root tip. Two transcriptional pathways, one mediated by PLETHORAs (PLTs) and the other by SHORTROOT (SHR) and SCARECROW (SCR), play major roles in root meristem development. The role of PLTs during root meristem development requires a concentration gradient, which is not only contributed by post-translational regulation such as growth dilution and intercellular movement, but also likely by a largely unknown fine-tuned transcriptional regulatory mechanism. We report here that Arabidopsis JANUS positively regulates PLT1 expression in the root meristem by recruiting RNA polymerase II (Pol II) to PLT1 and by interacting with PLT1. JANUS-dependent recruitment of Pol II is inhibited through the competitive binding of JANUS by GRF-INTERACTING FACTOR1/ANGUSTIFOLIA3 (GIF1/AN3), a transcriptional co-factor that negatively regulates PLT1 expression. Finally, GIF1 and JANUS, the antagonistic regulators of PLT1, both depend on Arabidopsis IMPORTIN β4 (IMB4) for their nuclear accumulation. The combination of an importin and its two antagonistic cargos in PLT1 transcription may have logistic benefits in fine-tuning the transcription of PLT1 in root meristem.

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