Plasmodiophora brassicae, the causal agent of clubroot disease, may penetrate plant cell walls via cellulase

Abstract

Plasmodiophora brassicae causes the clubroot disease of Brassicaceae by its obligate biotrophic lifestyle within host roots. The pathogen enters the root cortex, but is soon found near the vascular tissue. There are basically two possibilities for the distribution of Plasmodiophora within the root tissue: 1. distribution by simultaneous division with the host cell or 2. by active migration from cell to cell. It has been shown that plasmodia of the pathogen are indeed able to penetrate plant cell walls. We have therefore begun to isolate a cellulase gene from the pathogen by using degenerated primers to different fungal cellulases. It was possible to amplify specifically a fragment from infected roots 14 days after inoculation which was not present in healthy roots and later time points of infection. The fragment was sequenced and showed high homology to various fungal cellulases. Cloning of the complete cDNA and expression analysis of the putative Plasmodiophora cellulase is in progress.