Abstract
BackgroundClubroot is an important disease caused by the obligate parasite Plasmodiophora brassicae that infects the Brassicaceae. As a soil-borne pathogen, P. brassicae induces the generation of abnormal tissue in the root, resulting in the formation of galls. Root infection negatively affects the uptake of water and nutrients in host plants, severely reducing their growth and productivity. Many studies have emphasized the molecular and physiological effects of the clubroot disease on root tissues. The aim of the present study is to better understand the effect of P. brassicae on the transcriptome of both shoot and root tissues of Arabidopsis thaliana.ResultsTranscriptome profiling using RNA-seq was performed on both shoot and root tissues at 17, 20 and 24 days post inoculation (dpi) of A. thaliana, a model plant host for P. brassicae. The number of differentially expressed genes (DEGs) between infected and uninfected samples was larger in shoot than in root. In both shoot and root, more genes were differentially regulated at 24 dpi than the two earlier time points. Genes that were highly regulated in response to infection in both shoot and root primarily were involved in the metabolism of cell wall compounds, lipids, and shikimate pathway metabolites. Among hormone-related pathways, several jasmonic acid biosynthesis genes were upregulated in both shoot and root tissue. Genes encoding enzymes involved in cell wall modification, biosynthesis of sucrose and starch, and several classes of transcription factors were generally differently regulated in shoot and root.ConclusionsThese results highlight the similarities and differences in the transcriptomic response of above- and below-ground tissues of the model host Arabidopsis following P. brassicae infection. The main transcriptomic changes in root metabolism during clubroot disease progression were identified. An overview of DEGs in the shoot underlined the physiological changes in above-ground tissues following pathogen establishment and disease progression. This study provides insights into host tissue-specific molecular responses to clubroot development and may have applications in the development of clubroot markers for more effective breeding strategies.
Highlights
Clubroot is an important disease caused by the obligate parasite Plasmodiophora brassicae that infects the Brassicaceae
These deteriorating cells would be unable to produce an active defence response and as such our RNA-seq analysis did not go beyond the 24 dpi reported
Our data indicate that Arabidopsis has a complex transcriptomic response to P. brassicae infection, and in general, the plant response to pathogen infection of the root is different between shoot and root
Summary
Clubroot is an important disease caused by the obligate parasite Plasmodiophora brassicae that infects the Brassicaceae. Clubroot, caused by the soil-borne obligate plant pathogen Plasmodiophora brassicae, is a serious disease of Brassica crops, such as the important oilseed canola, resulting in decreased yields in Canada and worldwide [1]. A previous proteomic study of Arabidopsis root and hypocotyls revealed that P. brassicae infection altered the abundance of 12% of proteins, mainly related to cell defence, differentiation, and general metabolism when compared to uninfected samples [7]. Susceptibility or resistance to P. brassicae infection and subsequent clubroot establishment are thought to be a result of the host’s ability to regulate primary metabolism, transcription factor activities (TFs), defence responses, and cell division [11]. Microarray analysis of Arabidopsis root transcriptional changes during distinct developmental stages of P. brassicae revealed the upregulation of auxin, cytokinin and brassinosteroid metabolism and signaling genes [12]. Expressed TF families primarily included WRKY, MYB, BHLH, AP2/ERF and ET-responsive families [13]
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