Functional categories of ESTs are broadly similar in all three parasitic plants
Photosynthetic gene expression is lost in the nonphotosynthetic P. aegyptiaca
Chlorophyll synthesis genes are expressed and selectively maintained in P. aegyptiaca
Analyses suggest a history of genome duplication in Orobanchaceae
Parasitism in flowering plants has evolved at least 11 times . Only one family, Orobanchaceae, comprises all major nutritional types of parasites: facultative, hemiparasitic (partially photosynthetic), and holoparasitic (nonphotosynthetic) . Additionally, the family includes Lindenbergia, a nonparasitic genus sister to all parasitic Orobanchaceae [3,4,5,6]. Parasitic Orobanchaceae include species with severe economic impacts: Striga (witchweed), for example, affects over 50 million hectares of crops in sub-Saharan Africa, causing more than $3 billion in damage annually . Although gene losses and increased substitution rates have been characterized for parasitic plant plastid genomes [5,8,9,10,11], the nuclear genome and transcriptome remain largely unexplored. The Parasitic Plant Genome Project (PPGP; http://ppgp.huck.psu.edu/)  is leveraging the natural variation in Orobanchaceae to explore the evolution and genomic consequences of parasitism in plants through a massive transcriptome and gene discovery project involving Triphysaria versicolor (facultative hemiparasite), Striga hermonthica (obligate hemiparasite), and Phelipanche aegyptiaca (Orobanche ; holoparasite). Here we present the first set of large-scale genomic resources for parasitic plant comparative biology. Transcriptomes of above-ground tissues reveal that, in addition to the predictable loss of photosynthesis-related gene expression in P. aegyptiaca, the nonphotosynthetic parasite retains an intact, expressed, and selectively constrained chlorophyll synthesis pathway.