Plasmodiophora brassicae causes clubroot on cruciferous plants and causes worldwide huge economical losses on important Brassica crops. P. brassicae infection produces large root galls, the clubroots, which can also affect the upper plant parts by reduced water and nutrient uptake and redirection of assimilates from leaves to roots. P. brassicae is an obligate biotrophic protist in the plasmodiophorids within the eukaryote supergroup of Rhizaria and is unrelated to other known plant pathogens. Plasmodiophorids can be parasites of plants and oomycetes. The recently released genome of P. brassicae is only the third in the poorly studied Rhizaria and the first plant pathogenic genome of this eukaryotic group. The P. brassicae genome was estimated to be 25.5 Mb in size and predicted to contain 9730 gene models. A transcriptome of P. brassicae and Spongospora subterranea, the potato scab pathogen was also presented. Consequently, for the first time large scale data for a eukaryotic plant pathogen group outside the fungi and oomycetes are now available. This review highlights selected characteristics of the P. brassicae genome including molecular events shown or predicted to take place in each phase of its life-cycle, such as manipulation of: 1) host primary metabolism, 2) plant hormone homeostasis, and 3) plant defense. Further, future directions and challenges in the P. brassicae and plasmodiophorid genomic research are discussed.