Abstract
Clubroot, caused by the plasmodiophorid pathogen Plasmodiophora brassicae, is one of the most serious diseases on Brassica crops worldwide and a major threat to canola production in western Canada. Host resistance is the key strategy for clubroot management on canola. Several clubroot resistance (CR) genes have been identified, but the mechanisms associated with these CR genes are poorly understood. In the current study, a label-free shotgun proteomic approach was used to profile and compare the proteomes of Brassica rapa carrying and not carrying the CR gene Rcr1 in response to P. brassicae infection. A total of 527 differentially accumulated proteins (DAPs) were identified between the resistant (with Rcr1) and susceptible (without Rcr1) samples, and functional annotation of these DAPs indicates that the perception of P. brassicae and activation of defense responses are triggered via an unique signaling pathway distinct from common modes of recognition receptors reported with many other plant–pathogen interactions; this pathway appears to act in a calcium-independent manner through a not-well-defined cascade of mitogen-activated protein kinases and may require the ubiquitin-26S proteasome found to be related to abiotic stresses, especially the cold-stress tolerance in other studies. Both up-regulation of defense-related and down-regulation of pathogenicity-related metabolism was observed in plants carrying Rcr1, and these functions may all contribute to the CR mediated by Rcr1. These results, combined with those of transcriptomic analysis reported earlier, improved our understanding of molecular mechanisms associated with Rcr1 and CR at large, and identified candidate metabolites or pathways related to specific resistance mechanisms. Deploying CR genes with different modes of action may help improve the durability of CR.
Highlights
The soil-borne plasmodiophorid pathogen Plasmodiophora brassicae Woronin causes the clubroot disease on Brassica crops, one of the most serious diseases on cruciferous vegetables and canola/oilseed rape worldwide (Dixon, 2009)
Successful root infection by P. brassicae was confirmed by clubroot symptoms on all plants carrying no Rcr1 at 26 and 42 dpi, respectively, while none of the plants carrying the clubroot resistance (CR) gene showed any root swelling (Figure 1A)
A quality-control measure used for shotgun proteomics based on the correlation between expression profiles among replicates, showed that biological replicates were separated clearly based on the presence or absence of Rcr1 (Figure 1B)
Summary
The soil-borne plasmodiophorid pathogen Plasmodiophora brassicae Woronin causes the clubroot disease on Brassica crops, one of the most serious diseases on cruciferous vegetables and canola/oilseed rape worldwide (Dixon, 2009). Genetic resistance is generally regarded as the most effective and practical approach to clubroot management, especially on canola (Peng et al, 2014a). Several clubroot resistance (CR) genes, mostly from European fodder turnips Rapifera), have been introduced into Brassica crops including oilseed rape (B. napus), rutabaga The breakdown of CR has been reported on Chinese cabbage, oilseed rape, and canola (Matsumoto et al, 2012; Diederichsen et al, 2014; Strelkov et al, 2015). To improve the durability of CR, CR genes with different modes of action may be employed by pyramiding or rotation and a better understanding of resistance mechanisms associated with specific CR genes can lay a good foundation for this approach
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
