Transcriptional regulation of PLETHORA1 in the root meristem through an importin and its two antagonistic cargos (Plant Cell)

Plant root growth is sustained by stem cells in the root meristems, and the stem cell fate is maintained by the quiescent center (QC). PLETHORA (PLT) protein gradients contribute to maintaining the root meristem cell fate, although the transcriptional regulatory mechanism that establishes the PLT gradient is still in question. To address this, Xiong et al. studied JANUS, one of the transcriptional regulators of PLT1. By downregulating JANUS transcription, the authors demonstrated its role on root meristem activity through transcriptional regulation of PLTs. Additionally, the author studied a JANUS-interacting Pol II, NRPB10, and its occupancy at the promoter region of PLT1. This suggested that JANUS activates the transcription of PLTs by recruiting RNA pol II to the PLT1 promoter. The authors also showed the involvement of the IMB4 importin (a protein that facilitates the movement of other proteins into the nucleus) in nuclear accumulation of JANUS. Finally, the authors showed the competitive interaction of GIF1 a (negative transcriptional regulator of PLTs) with JANUS. The authors suggest two antagonistic PLT regulators, GIF1 and JANUS, compete for same importin for nuclear accumulation and that this contributes to the spatiotemporal regulation of the transcription of PLT1 to its gradient during root development. (Summary by Sunita Pathak @psunita980) Plant Cell 10.1105/tpc.20.00108