Transcriptional responses in the hemiparasitic plant Triphysaria versicolor to host plant Signals

Parasitic plants in the Scrophulariaceae use chemicals released by host pla nt roots to signal developmental processes critical for heterotrophy. Haust oria, parasitic plant structures that attach to and invade host roots, deve lop on roots of the hemiparasitic plant Triphysaria versicolor within a few hours of exposure to either maize (Zea mays) root exudate or purified haus toria-inducing factors. We prepared a normalized, subtractive cDNA library enriched for transcripts differentially abundant in T. versicolor root tips treated with the allelopathic quinone 2,6-dimethoxybenzoquinone (DMBQ). No rthern analyses estimated that about 10% of the cDNAs; represent transcript s strongly up-regulated in roots exposed to DMBQ. Northern and reverse nort hern analyses demonstrated that most DMBQ-responsive messages were similarl y up-regulated in T. versicolor roots exposed to maize root exudates. From the cDNA sequences we assembled a unigene set of 137 distinct transcripts a nd assigned functions by homology comparisons. Many of the proteins encoded by the transcripts are predicted to function in quinone detoxification, wh ereas others are more likely associated with haustorium. development. The i dentification of genes transcriptionally regulated by haustorium-inducing f actors provides a framework for dissecting genetic pathways recruited by pa rasitic plants during the transition to heterotrophic growth.