Changes in phenylpropanoid pathway gene expression in roots and leaves of susceptible and resistant Brassica napus lines in response to Plasmodiophora brassicae inoculation

Abstract

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is currently one of the most severe diseases of the Brassicaceae. As a soil-borne pathogen, P. brassicae infects the roots of host plants, inducing the formation of galls and negatively affecting plant growth and productivity. Roots and leaves of two clubroot susceptible and one resistant Brassica napus lines, inoculated with P. brassicae spores, were monitored for disease progression at four time points after inoculation. Quantitative gene expression analysis of phenylpropanoid pathway genes in these tissues showed increased expression of several genes involved in lignin biosynthesis in response to infection. In leaves, a higher expression of genes involved in flavonoid biosynthesis was also observed. In both roots and leaves of the resistant line, phenylpropanoid pathway genes were upregulated at more time points and at higher levels than in susceptible lines. The differential expression of phenylpropanoid pathway genes between resistant and susceptible lines, suggests that this pathway is instrumental in resistance to clubroot disease progression in the resistant line.