Molecular Basis of Verticillium dahliae Pathogenesis on Potato

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El-Bebany, Ahmed Farag A. M.
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Verticillium wilt is a serious disease in a wide range of economic crops worldwide. Verticillium wilt of potato is caused, primarily, by the fungus Verticillium dahliae. Disease management requires understanding of V. dahliae pathogenesis and interactions with potato, which was the main objective of this study. A differential potato-V. dahliae pathosystem was established where pathogenicity of four V. dahliae isolates with different levels of aggressiveness was evaluated on two potato cultivars, Kennebec (susceptible) and Ranger Russet (moderately resistant). External and internal symptoms and growth measurements revealed that isolates Vd1396-9 and Vs06-14 are highly and weakly aggressive, respectively. These two isolates were selected for transcriptomics and proteomics investigations to identify pathogenicity-related factors. Transciptomics analysis was conducted in both isolates after elicitation by root extracts from either Kennebec or Ranger Russet using a combinational approach involving subtractive hybridization and cDNA-AFLP. A total of 573 differentially expressed transcripts were detected in one or the other isolate. Among them, 185 transcripts of interest were recovered, re-amplified, sequenced and searched against NCBI and the Broad Institute V. dahliae genome databases for identification. The two contrasting-aggressiveness isolates were used for a comparative proteomics investigation. The first proteomic map of V. dahliae was established. The proteomics analysis was carried out using 2-Dimentional electrophoresis and mass spectrometry. Twenty five proteins were differentially expressed and identified in one or the other isolate. Many of the identified genes/proteins showed potential involvement in pathogenesis of V. dahliae or other fungi. Genes of stress response regulator A (oxidative stress tolerance factor), isochorismatase hydrolase (potential plant defense suppressor) and tetrahydroxynaphthalene reductase (involved in melanin and microsclerotia formation) were isolated from both isolates and cloned. Sequence analysis of these genes showed many differences that may explain their differential expression in the two isolates. Given that some of the identified genes/proteins are potentially involved in overcoming and suppressing plant defense, phenolics were profiled in Kennebec-inoculated with Vd1396-9 or Vs06-14 isolate. Chlorogenic, caffeic, ferulic acids, cis-jasmone and rutin accumulation showed variations after inoculation. The results obtained from this study will help understanding the V. dahliae-potato interactions and develop efficient strategies to control Verticillium wilt disease.
Verticillium dahliae, Potato, Pathogenesis, Pathogenicity-related factors, SH-cDNA-AFLP, Proteomics, Phenolics
El-Bebany, A. F., Rampitsch, C., and Daayf, F. 2010. Proteomic analysis of the phytopathogenic soilborne fungus Verticillium dahliae reveals differential protein expression in isolates that differ in aggressiveness. Proteomics 10: 289-303. DOI 10.1002/pmic.200900426