Loss of PMR4 callose synthase confers jasmonic acid-dependent resistance to the clubroot disease in Arabidopsis and Brassica napus

Growing clubroot-resistant cultivars is the most effective and practical control strategy, but resistance genes can often be overcome by emerging pathotypes. In this study, we identified PMR4 as a potential host susceptibility factor that can be targeted as a novel genetic resource for durable clubroot resistance.

Recessive PMR4 mutations in Arabidopsis thaliana conferred strong resistance to multiple P. brassicae pathotypes, independent of salicylic acid-mediated plant immunity. Using CRISPR/Cas9, we edited two PMR4 orthologs in the Brassica napus genome, and the resulting homozygous mutants exhibited resistance to both powdery mildew and clubroot diseases. While PMR4 is known to mediate callose deposition at wound and powdery mildew infection sites in leaves, this study reveals that P. brassicae infection induces callose deposition in Arabidopsis and B. napus roots in a PMR4-dependent manner.