Understanding the Resistance Mechanism in Brassica napus to Clubroot Caused by Plasmodiophora brassicae

Abstract

Exploring the mechanism of plant resistance has become the basis for selection of resistance varieties but reports on revealing resistant mechanism in Brassica napus against Plasmodiophora brassicae are rare. In this study, RNA-seq was conducted in the clubroot-resistant B. napus breeding line ZHE-226 and in the clubroot-susceptible rapeseed cultivar Zhongshuang 11 at 0, 3, 6, 9, and 12 days after inoculation. Strong alteration was detected specifically in ZHE-226 as soon as the root hair infection happened, and significant promotion was found in ZHE-226 on cell division or cell cycle, DNA repair and synthesis, protein synthesis, signaling, antioxidation, and secondary metabolites. Combining results from physiological, biochemical, and histochemical assays, our study highlights an effective signaling in ZHE-226 in response to P. brassicae. This response consists of a fast initiation of receptor kinases by P. brassicae; the possible activation of host intercellular G proteins which might, together with an enhanced Ca2+ signaling, promote the production of reactive oxygen species; and programmed cell death in the host. Meanwhile, a strong ability to maintain homeostasis of auxin and cytokinin in ZHE-226 might effectively limit the formation of clubs on host roots. Our study provides initial insights into resistance mechanism in rapeseed to P. brassicae.

Transcriptome and Coexpression Network Analyses Reveal Hub Genes in Chinese Cabbage (Brassica rapa L. ssp. pekinensis) During Different Stages of Plasmodiophora brassicae Infection

“…Many studies conducted to date have focused on molecular mechanisms aided by “-omics” approaches, such as RNA-seq. Mei et al (2019) reported great differences between two rapeseed genotypes, especially in the activation of signaling networks, the production of reactive oxygen species (ROS) and the programmed cell death (PCD) response to P. brassicae ( Mei et al, 2019 ). Chu et al (2014) found that the genes involved in the jasmonate (JA) and ethylene (ET) signaling and metabolic pathways and the defensive deposition of callose were significantly upregulated in clubroot-resistant plants compared to their levels in susceptible lines at 15 days after infection ( Chu et al, 2014 ).…”

CRb and PbBa8.1 Synergically Increases Resistant Genes Expression upon Infection of Plasmodiophora brassicae in Brassica napus

“…PTI is involved in the induction of plant hormone signal transduction and plant-pathogen interaction at the late stage of B. rapa resistant lines containing the CRd gene when exposed to P. brassicae [28]. In contrast, in the B. rapa near-isogenic line (CR BJN3-2) and B. napus resistance line (ZHE-226), no significant changes were detected when compared with the susceptible lines after inoculation with P. brassicae [13,15]. In this study, in comparison, we could not detect a significant interaction between the host and pathogen in the first defense mechanism, which might be due to pathogen effector proteins which have evolved to suppress the PTI; however, further study is required.…”

“…ROS is a well-known secondary messenger in cellular processes, and RBOHs are critical enzymes that produce ROS in response to hormonal and environmental signals and are activated by Ca 2+ [42,43]. ROS-associated signaling that suppresses pathogen growth determines PCD and HR [15]. It also works with other signaling molecules and induces SA and its regulators, the NPR1 and TGA transcription factors [44], and ROS-mediated defense plays a central key role in cross-talk with other molecular mechanisms, having great potential for resistant genotype selection [45].…”

“…Previously, a number of research articles published transcriptome analysis results of the defense responses of Brassica crops against P. brassicae at early infection stages at different time points, and resistant and susceptible lines were compared [13,14]. The results of these studies have shown that despite the presence of more robust effector-triggered immunity, the salicylic acid (SA) signaling pathway plays a pivotal role in clubroot resistance in Brassica rapa, which contains the CRb resistance gene [13], and strongly and rapidly accelerates receptor kinase and G proteins in B. napus (ZHE-226) resistance lines that contain the PbBa8.1 resistance gene, which may trigger reactive oxygen species (ROS), programed cell death (PCD), and the hormonal signal transduction signaling pathway [15]. The current study is different from previously published work.…”

Transcriptome analysis of rice leaves in response to Rhizoctonia solani infection

“…A set of time-scale transcriptome analysis revealed that functional ETI (effector triggered immunity) responses rely on an appropriate time point for transcriptional reprogramming, which is mediated by jasmonate, ethylene, salicylic acid, and PAD4 signaling (19). Transcriptome analysis provided useful information for understanding the resistance mechanism of Brassica napus to clubroot disease (20) and was performed to investigate the regulatory mechanism of Pi9 and Pi21, two R (resistance genes) that control blast fungus (21,22).…”