Spatiotemporal regulation of cell-cycle genes by SHORTROOT links patterning and growth

In higher animals and plants the processes of growth and patterning are coordinated. Much is known about the genes regulating patterning and many genes have been identified that are involved in cell-cycle control, but there are few instances in which a connection has been made between the two. A study of patterning in Arabidopsis root now shows that two key regulators of root-organ patterning directly control the transcription of specific components of the cell-cycle machinery. This demonstrates a direct link between developmental regulators, components of the cell-cycle machinery and organ patterning. In higher animals and plants, the processes of growth and patterning are coordinated. In this study, the authors study patterning in Arabidopsis root and show that two key regulators of root organ patterning directly control the transcription of specific components of the cell-cycle machinery. This study provides a direct link between developmental regulators, components of the cell-cycle machinery and organ patterning. The development of multicellular organisms relies on the coordinated control of cell divisions leading to proper patterning and growth1,2,3. The molecular mechanisms underlying pattern formation, particularly the regulation of formative cell divisions, remain poorly understood. In Arabidopsis, formative divisions generating the root ground tissue are controlled by SHORTROOT (SHR) and SCARECROW (SCR)4,5,6. Here we show, using cell-type-specific transcriptional effects of SHR and SCR combined with data from chromatin immunoprecipitation-based microarray experiments, that SHR regulates the spatiotemporal activation of specific genes involved in cell division. Coincident with the onset of a specific formative division, SHR and SCR directly activate a D-type cyclin; furthermore, altering the expression of this cyclin resulted in formative division defects. Our results indicate that proper pattern formation is achieved through transcriptional regulation of specific cell-cycle genes in a cell-type- and developmental-stage-specific context. Taken together, we provide evidence for a direct link between developmental regulators, specific components of the cell-cycle machinery and organ patterning.