Microbe Profile: Plasmodiophora brassicae, the gall-forming protist behind clubroot disease.

Plasmodiophora brassicae is a soil-borne intracellular obligate biotrophic protist and the causal agent of clubroot disease in Brassicaceae. Phylogenetically placed within the Rhizaria supergroup, it exhibits a complex two-stage life cycle leading to the formation of club-shaped galls, driven by phytohormone and effector-mediated host reprogramming. A recently obtained telomere-to-telomere genome assembly of the Canadian pathotype Pb3A revealed a compact genome structure encoding a complex secretome. Despite its agronomic relevance, key aspects of its biology, including the existence of sexual reproduction, host specificity determinants and effector biology, remain poorly understood, due to its unculturable nature and limited genomic resources.