Higher plants have developed remarkable plasticity in response to extrinsic cues, generating new organs throughout their lifespan via pluripotent stem cells in meristems. Maintenance and homeostasis of the stem cell niche (SCN) in Arabidopsis roots are essential for the growth and development of all root cell types and is regulated by feedback signaling involving key transcription factors, phytohormones, peptide ligands, and receptors. However, the tight but dynamic regulation of the transition from stem cell fate to differentiation remains largely elusive.
The root SCN centers around a quiescent center (QC) maintaining stemness. The transcription factors WUSCHEL-RELATED HOMEOBOX 5 (WOX5) and PLETHORAs (PLTs) are expressed in the SCN and maintain the QC and regulate distal columella stem cell (CSC) fate. We found that both WOX5 and PLTs are crucial for root meristem maintenance, coordinating QC quiescence and CSC fate. Notably, PLTs, particularly PLT3, contain intrinsically disordered regions with prion-like domains (PrDs) necessary for complex formation with WOX5 and recruitment to nuclear bodies (NBs) in CSCs. The subsequent dynamic partitioning of PLT-WOX5 complexes to NBs, possibly via liquid-liquid phase separation, plays a pivotal role in determining CSC fate.
This novel regulatory model involving dynamic condensate formation suggests that dynamic subnuclear localization of TF complexes integrates external cues with molecular-level stem cell regulation, shedding light on plant growth and adaptability to environmental challenges.