Natural variation in Arabidopsis responses to Plasmodiophora brassicae reveals an essential role for Resistance to Plasmodiophora brasssicae 1 (RPB1)

Abstract

SUMMARYDespite the identification of clubroot resistance genes in various Brassica crops our understanding of the genetic basis of immunity to Plasmodiophora brassicae infection in the model plant Arabidopsis thaliana remains limited. To address this issue, we performed a screen of 142 natural accessions and identified 11 clubroot‐resistant Arabidopsis lines. Genome‐wide association analysis identified several genetic loci significantly linked with resistance. Three genes from two of these loci were targeted for deletion by CRISPR/Cas9 mutation in resistant accessions Est‐1 and Uod‐1. Deletion of Resistance to Plasmodiophora brassicae 1 (RPB1) rendered both lines susceptible to the P. brassicae pathotype P1+. Further analysis of rpb1 knock‐out Est‐1 and Uod‐1 lines showed that the RPB1 protein is required for activation of downstream defence responses, such as the expression of phytoalexin biosynthesis gene CYP71A13. RPB1 has recently been shown to encode a cation channel localised in the endoplasmic reticulum. The clubroot susceptible Arabidopsis accession Col‐0 lacks a functional RPB1 gene; when Col‐0 is transformed with RPB1 expression driven by its native promoter it is capable of activating RPB1 transcription in response to infection, but this is not sufficient to confer resistance. Transient expression of RPB1 in Nicotiana tabacum induced programmed cell death in leaves. We conclude that RPB1 is a critical component of the defence response to P. brassicae infection in Arabidopsis, acting downstream of pathogen recognition but required for the elaboration of effective resistance.

Plant NLR immunity activation and execution: a biochemical perspective

“…Because the Arabidopsis ZAR1 and wheat Sr35 oligomers induced Ca 2+ influx in cultured Xenopus oocytes [78,79], it is thought that CNL resistosomes represent an entirely new type of autonomous ion channel in plants. Remarkably, a small protein, WeiTsing (WTS encoded by the Arabidopsis Resistance to Plasmodiophora brassicae 1 RPB1 gene [84]) expressed in Arabidopsis roots and unrelated to CNLs or other known plant ion channels, was reported to confer broad spectrum resistance to the Plasmodiophora brassicae pathogen causing club-root disease by forming a pentameric Ca 2+ -permeable ion channel at endoplasmic reticulum membranes [85]. How Ca 2+ influx into the cytoplasm by CNL resistosomes or a WTS membrane channel are coordinated with canonical ion channel activities known to contribute to immunity remains unclear [81][82][83].…”

New insight into Ca2+‐permeable channel in plant immunity

“…Although our knowledge of Ca 2+ release from the ER in plants is limited compared with that in animals, increasing evidence supports a crucial role for Ca 2+ release from the ER by ER‐localized Ca 2+ ‐permeable channels in regulating Ca 2+ signaling in different aspects of plant biology, particularly plant immunity (He et al, 2021). A recent study identified a resistance gene, WeiTsing ( WTS ), that encodes an ER‐localized Ca 2+ ‐permeable channel and confers broad‐spectrum resistance against Plasmodiophora brassicae in both Arabidopsis and Brassica napus (Ochoa et al, 2023; Wang et al, 2023b). WTS expression is highly induced exclusively in the pericycle upon P. brassicae infection, and WTS subsequently induces the expression of multiple immune‐related genes (Wang et al, 2023b).…”

A Basic Guide to the Propagation and Manipulation of the Clubroot Pathogen, Plasmodiophora brassicae

“…Cultural practices such as crop rotation and sanitation are being implemented to minimize the disease's spread and impact (Hwang et al., 2012; Javed et al., 2023). However, the most effective current management strategy involves the development of resistant plant varieties capable of withstanding P. brassicae infection (Ochoa et al., 2023). Nonetheless, it is important to note that new clubroot pathogen isolates have demonstrated the ability to overcome various clubroot‐resistant profiles in commercial canola cultivars (Hwang et al., 2019).…”