Roots grow through continuous production of cells in apically positioned meristem and their displacement to elongation and differentiation zones, where they expand several times and obtain characteristics of mature cells. Brassinosteroids (BRs) are a group of plant hormones, which coordinate root growth by regulating both cell division and expansion. I have previously established that optimal root growth in Arabidopsis requires BR concentrations low in the meristem and high in the root elongation zone. This is achieved through regulation of expression levels of BR biosynthetic enzymes that can locally determine levels of hormone production. Preliminary findings of my work also imply that the low BR production in the root meristem is maintained by asymmetric expression of the rate-limiting enzyme DWARF4 (DWF4) that is coupled to cell division through a yet unknown mechanism. In this project, I will use advanced live cell imaging techniques, and I will employ state of the art single-cell RNA sequencing technology to reveal the molecular mechanism controlling the DWF4 expression pattern. Finally, I will demonstrate its importance for overall root growth. The findings in this project will contribute to our understanding of coordination of cell division and expansion processes during organ growth in plants.