The dual function of EMB1579 in transcription and splicing governs tissue patterning in the Arabidopsis root meristem

In the root meristem of Arabidopsis, stem cell maintenance depends on the coordinated action of transcription factor networks. The transcriptional regulator EMBRYO DEFECTIVE 1579 (EMB1579), a protein that forms nuclear condensates, regulates plant growth. However, the molecular mechanisms through which it functions in the root meristem remain largely unclear. Here, we show that EMB1579 is required for stem cell maintenance and proper cell division orientation. EMB1579 modulates the function of two root stem cell regulatory modules, PLETHORAs and SCARECROW-SHORT-ROOT, through a process involving transcriptional regulation and RNA splicing. We show that EMB1579 acts as a catalyst for stem cell gene expression, and its activity is fine-tuned by its physical association with RNA splicing factors. The formation of nuclear condensates is essential for EMB1579 function in the root meristem. Our findings reveal a mechanism by which EMB1579 regulates stem cell determinants in the root meristem and expand the understanding of gene regulation complexity in plant development.