Discovery of clubroot-resistant genes in Brassica napus by transcriptome sequencing

Multi-Omics Approaches to Improve Clubroot Resistance in Brassica with a Special Focus on Brassica oleracea L

Brassica oleracea is an agronomically important species of the Brassicaceae family, including several nutrient-rich vegetables grown and consumed across the continents. But its sustainability is heavily constrained by a range of destructive pathogens, among which, clubroot disease, caused by a biotrophic protist Plasmodiophora brassicae, has caused significant yield and economic losses worldwide, thereby threatening global food security. To counter the pathogen attack, it demands a better understanding of the complex phenomenon of Brassica-P. brassicae pathosystem at the physiological, biochemical, molecular, and cellular levels. In recent years, multiple omics technologies with high-throughput techniques have emerged as successful in elucidating the responses to biotic and abiotic stresses. In Brassica spp., omics technologies such as genomics, transcriptomics, ncRNAomics, proteomics, and metabolomics are well documented, allowing us to gain insights into the dynamic changes that transpired during host-pathogen interactions at a deeper level. So, it is critical that we must review the recent advances in omics approaches and discuss how the current knowledge in multi-omics technologies has been able to breed high-quality clubroot-resistant B. oleracea. This review highlights the recent advances made in utilizing various omics approaches to understand the host resistance mechanisms adopted by Brassica crops in response to the P. brassicae attack. Finally, we have discussed the bottlenecks and the way forward to overcome the persisting knowledge gaps in delivering solutions to breed clubroot-resistant Brassica crops in a holistic, targeted, and precise way.

Integrating long noncoding RNAs and mRNAs expression profiles of response to Plasmodiophora brassicae infection in Pakchoi (Brassica campestris ssp. chinensis Makino)

The biotrophic protist Plasmodiophora brassicae causes serious damage to Brassicaceae crops grown worldwide. However, the molecular mechanism of the Brassica rapa response remains has not been determined. Long noncoding RNA and mRNA expression profiles in response to Plasmodiophora brassicae infection were investigated using RNA-seq on the Chinese cabbage inbred line C22 infected with P. brassicae. Approximately 5,193 mRNAs were significantly differentially expressed, among which 1,345 were upregulated and 3,848 were downregulated. The GO enrichment analysis shows that most of these mRNAs are related to the defense response. Meanwhile, 114 significantly differentially expressed lncRNAs were identified, including 31 upregulated and 83 downregulated. Furthermore, a total of 2,344 interaction relationships were detected between 1,725 mRNAs and 103 lncRNAs with a correlation coefficient greater than 0.8. We also found 15 P. brassicaerelated mRNAs and 16 lncRNA interactions within the correlation network. The functional annotation showed that 15 mRNAs belong to defense response proteins (66.67%), protein phosphorylation (13.33%), root hair cell differentiation (13.33%) and regulation of salicylic acid biosynthetic process (6.67%). KEGG annotation showed that the vast majority of these genes are involved in the biosynthesis of secondary metabolism pathways and plant-pathogen interactions. These results provide a new perspective on lncRNA-mRNA network function and help to elucidate the molecular mechanism of P. brassicae infection.

Proto-oncogenes in a eukaryotic unicellular organism play essential roles in plasmodial growth in host cells

BACKGROUND

The eukaryotic unicellular protist Plasmodiophora brassicae is an endocellular parasite of cruciferous plants. In host cortical cells, this protist develops a unicellular structure that is termed the plasmodium. The plasmodium is actually a multinucleated cell, which subsequently splits and forms resting spores. The mechanism for the growth of this endocellular parasite in host cell is unclear.

RESULTS

Here, combining de novo genome sequence and transcriptome analysis of strain ZJ-1, we identified top five significant enriched KEGG pathways of differentially expressed genes (DEGs), namely translation, cell growth and death, cell communication, cell motility and cancers. We detected 171 proto-oncogenes from the genome of P. brassicae that were implicated in cancer-related pathways, of which 46 were differential expression genes. Three predicted proto-oncogenes (Pb-Raf1, Pb-Raf2, and Pb-MYB), which showed homology to the human proto-oncogenes Raf and MYB, were specifically activated during the plasmodial growth in host cortical cells, demonstrating their involvement in the multinucleate development stage of the unicellular protist organism. Gene networks involved in the tumorigenic-related signaling transduction pathways and the activation of 12 core genes were identified. Inhibition of phosphoinositol-3-kinase relieved the clubroot symptom and significantly suppressed the development process of plasmodia.

CONCLUSIONS

Proto-oncogene-related regulatory mechanisms play an important role in the plasmodial growth of P. brassicae.