How and where to build a root hair

The root hair of Arabidopsis has become a model system for investigations o f the patterning and morphogenesis of cells in plants. A cascade of transcr iptional regulators controls the pattern of cellular differentiation. Recen tly, one of the genes that plays a specific role in cellular differentiatio n in roots, WEREWOLF, has been shown to be functionally equivalent to GLABR A 1, which functions only in the shoot. The cloning of genes defined by mut ants with defective root-hair growth has provided insights into the roles o f the cell wall, ion transport and the cytoskeleton during hair growth. Gen etic analyses continue to identify mutants that will be instructive in furt hering our understanding of the growth and development of root-hair cells.