title: Verticillium dahliae's Isochorismatase Hydrolase Is a Virulence Factor That Contributes to Interference With Potato's Salicylate and Jasmonate Defense Signaling.
abstract: This study aimed to dissect the function of the Isochorismatase Hydrolase (ICSH1) gene inVerticillium dahliae's pathogenesis on potato.VdICSH1was up-regulated inV. dahliaeafter induction with extracts from potato tissues. Its expression increased more in response to root extracts than to leaf and stem extracts. However, such expression in response to root extracts was not significantly different in the highly and weakly aggressive isolates tested. During infection of detached potato leaves,VdICSH1expression increased significantly in the highly aggressive isolate compared to the weakly aggressive one. We generatedicsh1mutants from a highly aggressive isolate ofV. dahliaeand compared their pathogenicity with that of the original wild type strain. The analysis showed that this gene is required for full virulence ofV. dahliaeon potatoes. When we previously found differential accumulation of ICSH1 protein in favor of the highly aggressive isolate, as opposed to the weakly aggressive one, we had hypothesized that ICSH would interfere with the host's defense SA-based signaling. Here, we measured the accumulation of both salicylic acid (SA) and jasmonic acid (JA) in potato plants inoculated with anicsh1mutant in comparison with the wild type strain. The higher accumulation of bound SA in the leaves in response to theicsh1mutant compared to the wild type confirms the hypothesis that ICSH1 interferes with SA. However, the different trends in SA and JA accumulation in potato in the roots and in the stems at the early infection stages compared to the leaves at later stages indicate that they are both associated to potato defenses againstV. dahliae. The expression of members of the isochorismatase family in theicsh1mutants compensate that of ICSH1 transcripts, but this compensation disappears in presence of the potato leaf extracts. This study indicates ICSH1's involvement inV. dahliae's pathogenicity and provides more insight into its alteration of the SA/JA defense signaling's networking.
authors.affiliation: Department of Plant Science, University of Manitoba, Winnipeg MB, Canada.
authors.forename: Xiaohan
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Plant Science, University of Manitoba, WinnipegMB, Canada; Department of Genetics, Faculty of Agriculture, University of TantaTanta, Egypt.
authors.forename: Atta
authors.initials: A
authors.lastname: Soliman
authors.affiliation: Department of Plant Pathology, Bangladesh Agricultural University Mymensingh, Bangladesh.
authors.forename: Md R
authors.initials: MR
authors.lastname: Islam
authors.affiliation: Department of Plant Science, University of Manitoba, Winnipeg MB, Canada.
authors.forename: Lorne R
authors.initials: LR
authors.lastname: Adam
authors.affiliation: Department of Plant Science, University of Manitoba, Winnipeg MB, Canada.
authors.forename: Fouad
authors.initials: F
authors.lastname: Daayf
keywords: ICSH1; isochorismatase; jasmonic acid; pathogenesis; salicylic acid; virulence factor