Proteome-level changes in the roots of Brassica napus as a result of Plasmodiophora brassicae infection

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, has emerged as an important new disease of canola (Brassica napus) in Alberta, Canada. Changes in the root protein profile were examined by two-dimensional gel electrophoresis at 12, 24, 48 and 72 h after inoculation of a susceptible canola genotype with the pathogen. A total of 20 protein spots were identified as either increasing (13 spots) or decreasing (7 spots) in intensity relative to water-treated controls. The identities of these proteins were established by MS/MS, and included proteins involved in lignin biosynthesis, cytokinin metabolism, glycolysis, intracellular calcium homeostasis, and the detoxification of ROS. Decreased abundance of adenosine kinase, which is involved in cytokinin homeostasis, supported previous reports indicating a key role for cytokinin in the early phases of clubroot infection. An approximately sixfold reduction in caffeoyl-CoA O-methyltransferase abundance suggested a reduction in host lignin biosynthesis after pathogen challenge, and is consistent with the compatible nature of the interaction examined. Interestingly, levels of enzymes involved in ROS metabolism declined sharply at 12 h after inoculation, but increased at 24–72 h. Collectively, these data suggest major changes in canola metabolism shortly after challenge by the pathogen, which may result in the susceptibility of the host.