For a plant embryo to grow from a single fertilized egg cell to a complex multicellular structure, it must undergo a highly ordered sequence of cell divisions, during which the emerging tissues are patterned and ultimately differentiate. In vascular plants, the vascular tissues lie deep within roots and shoots, where they provide the main mechanism for transporting water and nutrients between organs. The specification of root vascular tissues provides an elegant system to investigate tissue patterning. It had previously been shown that two plant hormones cross regulate each other's activity and transport to control vascular patterning (1). However, on page 636 of this issue, De Rybel et al. (2) identify a new interaction between these hormones through the regulation of their local synthesis, such that collectively these hormonal interactions coordinate the processes of both cell division and tissue patterning to specify the stereotypical vascular pattern in Arabidopsis embryos.
Via Francis Martin, Christophe Jacquet