Turning ON the switch--RhoGEFs in plants.

Plant ROPs (or RACs) are Ras-related, small GTP-binding proteins that function as molecular switches in numerous signaling cascades. ROPs (RACs) cycle between a GDP-bound, inactive state and a GTP-bound, active state. Activation requires guanine-nucleotide exchange factors (GEFs), which were not identified in plants until recently. Alfred Wittinghofer and co-workers' description of a group of plant-specific RhoGEFs opens the way for the elucidation of ROP signaling cascades from membrane receptors to responses.