Identification and characterization of pathogenicity-related factors in Verticillium dahliae
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Date
2019-09
Authors
Zhu, Xiaohan
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Abstract
Verticillium dahliae is the main causal agent of potato early dying (PED) disease in Canada and can lead to yield losses of up to 50%. The management of this disease is usually costly and inefficient. Therefore, it is important to understand the molecular interaction between the host and pathogen, in order to determine the key components leading to disease or resistance.
Dr. Daayf’s lab previously identified several proteins and/or genes showing differentiatial activity between highly and weakly aggressive V. dahliae isolates. Isochorismatase Hydrolase, NADPH oxidases, exopolygalacturonase, Ras-GAP like protein, serine/threonine-protein kinase, Ubiquitin-conjugating enzyme variant MMS2, NADH-ubiquinone oxidoreductase, Thioredoxin, Pyruvate dehydrogenase E1 component subunit beta, myo-inositol 2-dehydrogenase, and HAD-superfamily hydrolases all showed higher activity in the highly aggressive isolate compared to the weakly aggressive one.
We hypothesized that Isochorismatase Hydrolase (VdICSH1) of V. dahliae may interfere with the SA synthesis pathway of potato during their interaction. We generated gene disruption mutants for VdICSH1 in the highly aggressive isolate, and showed their reduced virulence compared with the wild type. Plant SA and JA accumulation showed different tendencies in the stems and roots at early infection stages, and similar tendencies in the leaves at later stages, when exposed to V. dahliae infection. It was also apparent that other isochorismatase family members in the icsh1 mutants compensate for the absence of ICSH1.
Further, we investigated the function of ROS generated by NADPH oxidases in V. dahliae, by generating mutants for NoxA, NoxB and NoxC in the highly aggressive isolate. The noxa and noxb mutants lost their penetration ability and could not form penetration pegs after 72h on cellophane membrane, which led to a significant decrease in their virulence on potato.
Finally, we employed a new vector–free split-marker recombination method, derived from Saccharomyces cerevisiae, to quickly obtain knock-out mutants for the exopolygalacturonase (ExoPG) gene in the highly aggressive V. dahliae isolate. This gene showed more transcriptional activity in response to leaf and stem extracts, as well as during early infection stage.
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Keywords
Verticillium dahliae, Pathogenicity, ICSH1, NoxA, NoxB, ExoPG
Citation
Zhu, X., Soliman, A., Islam, M.R., Adam, L.R., and Daayf, F. (2017). Verticillium dahliae’s isochorismatase hydrolase is a virulence factor that contributes to interference with potato’s salicylate and jasmonate defense signaling. Frontiers in plant science 8: 399.