At least 19 species belonging to 14 different families in both mono cot and dicot clades are selleck compound natural hosts of T. versicolor, and multiple hosts are often parasitized simultaneously Inhibitors,Modulators,Libraries by T. versicolor in the fields. Therefore, having the ability to recognize a multitude of host factors from such Inhibitors,Modulators,Libraries a wide range of hosts would confer this parasitic species an evolutionary advantage. We hypothesize that parasitic plants might have evolved a mechanism to exploit the abundant allelopathic chemicals in their environment and turn the phytotoxicity they initially encountered into a haustorium inducing cue for their benefit. Mainten ance of TvQR1 molecular diversity could be a mechan ism enabling this evolutionary process.

High level of nucleotide diversity in synonymous sites as well as in non synonymous sites of TvQR1 may suggest that the long term selection has been acting on this gene, as it is expected to elevate nucleotide diversity of closely linked sites while non synonymous sites are more likely Inhibitors,Modulators,Libraries to be the direct target Inhibitors,Modulators,Libraries of selection. Those patterns are indeed observed in the plant R genes that are suggested to be under long term balancing selection. TvPirin, on the other hand, as a transcription co factor, probably interacts with other proteins with specific conformations for DNA binding, and thus would be subject to more evolutionary constraints in order to maintain specific protein protein interactions, which might have led to the much lower molecular diversity observed here. Conclusions Our molecular analysis has shown that, in the natural T.

versicolor populations from Northern California, the only two genes known to date to be required for hau storium initiation, TvQR1 and TvPirin, display highly contrasting patterns of molecular polymorphisms. Espe cially, the nucleotide diversity of TvQR1 is 97 times higher than Inhibitors,Modulators,Libraries that of TvPirin, suggesting that these two genes would have been subjected to different selective pressures, possibly reflecting their distinct roles in phytochemical perception during host recognition. This difference is further manifest in their differential regula tion by HIFs and non HIFs. Since TvQR1 responds to both HIFs and non HIFs, it might not only function in haustorium development but also in the oxidative stress response. The non toxic selleck inhibitor HIF peonidin provides a useful tool to dissect these two pathways in future search for additional parasitic plant genes involved in haustorium development. Differential responses of parasitic genes under peonidin, other toxic HIFs, and toxic non HIFs bear the potential to separate genes only involved in the detoxification pathway from genes specific to the haustorium signaling pathway. Furthermore, although peonidin is a very effective HIF in T.