XVI International Botanical Congess

The temporal and spatial control of the transition from vegetative to parasitic mode is critical to any parasite, but essential to the sessile parasitic plants. This transition in Striga spp. Has been proposed to be controlled by constitutive production of activated oxygen species (AOS) at the Striga root meristem. This strategy allows a parasite to exploit abundant host enzymes to exidatively generate a diffusible xenognostic quinone signal from host cell wall phenols. The quinone signals are recognized via a parasite redox receptor, possible via existing defense pathways, to regulate the temporal and spatial commitment of haustorial development. Critical downstream genes, most notable the cell enlarging enzyme expansin, have been now identified and correlated with the commitment to haustorial development. Analysis of these molecular markers has made it possible to develop a complete model for the signaling event initiating haustorial development. The characterization of these events offers insight into the functional evolution of the parasitic plants.