Arabidopsis thaliana expressing PbBSMT, a gene encoding a SABATH‐type methyltransferase from the plant pathogenic protist Plasmodiophora brassicae, show leaf chlorosis and altered host susceptibility

Abstract

The plant pathogenic protist Plasmodiophora brassicae causes clubroot disease of Brassicaceae. This biotrophic organism can down-regulate plant defence responses. The previously characterised P. brassicae PbBSMT methyltransferase has substrate specificity for salicylic, benzoic and anthranilic acids. We therefore propose a role for the methylation of SA in attenuating plant defence response in infected roots as a novel strategy for intracellular parasitism. We overexpressed PbBSMT under the control of an inducible promoter in Arabidopsis thaliana and performed physiological, molecular and phytopathological analyses with the transgenic plants under control and induced conditions in comparison to the wild type. Upon induction, transcription of PbBSMT was associated with: (1) strong leaf phenotypes from anthocyanin accumulation and chlorosis followed by browning; (2) increased plant susceptibility after infection with P. brassicae that was manifested as more yellow leaves and reduced growth of upper plant parts; and (3) induced transgenic plants were not able to support large galls and had a brownish appearance of some clubs. Microarray data indicated that chlorophyll loss was accompanied by reduced transcription of genes involved in photosynthesis, while genes encoding glucose metabolism, mitochondrial functions and cell wall synthesis were up-regulated. Our results indicate a role for PbBSMT in attenuation of host defence responses in the roots by metabolising a plant defence signal.

Demystifying biotrophs: FISHing for mRNAs to decipher plant and algal pathogen–host interaction at the single cell level

“…3). These results again confirm findings from previous studies 27,33 , but our results are the first to pinpoint these changes to specific life cycle stages. Notably PbBSMT mRNAs accumulate around the developing resting spores in the sporogenic plasmodia (Fig.…”

“…MeSA was specifically emitted from Arabidopsis leaves infected with P. brassicae 33 . Combined with findings from previous studies 27,33,48 , our observations strongly support the role in host defence suppression of PbBSMT, making it a very interesting target for future studies.…”

“…This methyltransferase has structural similarities to plant methyltransferases and is able to methylate SA, but with a much higher efficacy in suppressing SA levels and its associated effects through methylation, than the plant methyltransferase 48 . Previous qPCR analysis of its expression pattern showed, that its expression during clubroot development is highest when the concentration of SA in the roots peaks, which is the reason why a role in disease development of this gene has been discussed 27,33 . In our in situ experiments, PbBSMT mRNAs started to appear in small developing plasmodia (Suppl.…”

North-Western Himalayan Common Beans: Population Structure and Mapping of Quantitative Anthracnose Resistance Through Genome Wide Association Study

“…We also found a gene model (Phvul.004G023900) that encodes a methyltransferase that impart quantitative resistance to race 503. The role of methyltransferases in plant disease resistance is well documented against an array of plant pathogens ( Yang et al, 2017 ; Wang et al, 2018 ; Bulman et al, 2019 ). Besides Pv04, this study identified a SNP on Pv09 for quantitative resistance against race 503 in gene model Phvul.009G169600 that encodes a zinc finger protein.…”

Identification of Plasmodiophora brassicae effectors — A challenging goal

“…Validation of the RNA-seq data through qPCR [77] or ddPCR [78], identification of the subcellular localization of the candidate effector proteins [20] through transient expression or stable transformation [21,79] and identification of the plant proteins interacting with the pathogen effectors are some of the logical next steps towards the identification of P. brassicae effector proteins. The work with pathogen effectors in general is challenging, but the work with intracellular, biotrophic pathogens appears to be even more so, requiring creativity and novel solutions.…”