Parasitic plants develop haustoria either near their root tips or along their stems in response to selective chemical factors sellectchem released by their hosts. The hau storium initiates via localized cell expansion and division that is coupled with haustorial hair growth in many spe cies. Following attachment and penetration of the hosts roots or stems, the haustorium establishes a vascular continuity between the parasite and its host through which water and nutrients are channeled Inhibitors,Modulators,Libraries to the parasite to benefit its own growth and development. By so doing, parasitic plants disturb many developmental and physio logical aspects of host plants. Consequently, parasitic plants have a tremendous impact on commu nity ecology among plants, animals, microbes, and even the surrounding physical environment.

Therefore, studies on parasitic plants Inhibitors,Modulators,Libraries encompass a range of interests, including anatomy and development, cellular physiology, gene regulation, population genetics, phyl ogeny, ecology and evolution. Here, we focus on a var iety of aspects of host perception and recognition by parasitic plants. The perception and recognition by parasitic plants of haustorium inducing factors Inhibitors,Modulators,Libraries released by host plants is best documented in root parasites of the Orobanchaceae family. The first three HIFs identified, xenognosin A, xenognosin B, and 2,6 dimethoxybenzoquinone, are phen olic compounds. Additionally, various quinone and flavonoid HIFs were subsequently identified and characterized. Further studies on HIF biogenesis, activity, and recognition in the two root hemiparasites Striga spp. and Triphysaria spp.

have shed light onto the chemical signaling by DMBQ, which is involved in the first steps of Inhibitors,Modulators,Libraries the haustorium developmental pathway. The genus Striga contains prolific weeds causing substantial damage to cereal crops mostly in Africa, whereas Triphysaria is a wild native genus in the grassland communities of Northern American coastlands. The current model for hau storium initiation proposes that certain unidentified peroxidases or laccases released by parasitic roots catalyze the production of DMBQ at the host contact site, which diffuses towards the parasitic plant. Next, a quinone oxidoreductase from the parasite converts DMBQ from its inactive form into the transi ently active single electron free radical form with the suitable redox potential for haustorium induction.

Inhibitors,Modulators,Libraries This process is hypothesized to be the first step of the hau storium organogenesis pathway. To date, only inhibitor Brefeldin A two parasitic plant genes involved in hau storium development have been identified, TvQR1 and TvPirin, both from the root parasite Triphysaria versicolor. The TvPirin protein is a general transcription co factor that up regulates several DMBQ responsive and non responsive genes. TvQR1 encodes the aforementioned quinone oxidoreductase, which catalyses the reduction of quinones.