Year: 2013
Type: dissertation
Abstract: The aim of this study was to characterize novel virulence or fitness genes of Pectobacterium wasabiae SCC3193 and Pectobacterium atrosepticum SCRI1043, which are potato pathogenic model strains. Members of the Pectobacterium genus cause plant diseases called soft rot, blackleg and aerial stem rot. Potato is one of the most economically important crops affected by these diseases. The Pectobacterium genus belongs to the bacterial family Enterobacteriaceae and is closely related to many common animal pathogens, such as Escherichia coli and Salmonella. Together, the bacteria belonging to genus Pectobacterium and to the other soft-rot genus Dickeya are called soft-rot enterobacteria. In this study, novel virulence genes were identified and characterized using genomic and post-genomic approaches. The study began by examining the genomic sequences of the model strains; functional studies of the genes were then conducted based on function predictions of the genes of interest. The genome of P. atrosepticum SCRI1043 was sequenced in 2004, and the genomes of P. wasabiae SCC3193 and the P. wasabiae type strain, which were used for comparative genomics, were sequenced by a collaborator of this study. The genome analyses revised the species designation of the model strain SCC3193 and the genome analyses together with transcriptional studies revealed candidates for novel virulence genes for post-genomic studies. In the post-genomic studies, the genes of interest were mutated and complemented by expression of the respective gene from a plasmid in the mutant background in several phenotypic experiments. The phenotypes of the novel mutant strains were evaluated in several virulence assays in potato and tobacco, motility assays, attachment assays, growth assays in several media, gene expression assays in several media and plant cell wall-degrading enzyme production measuring assays, all in comparison to the wild-type strain and the complemented strain. Plant cell wall-degrading enzymes are the main pathogenicity factors in genus Pectobacterium; the other tested functions are known to be related to virulence or may be related to virulence. Novel virulence determinants were suggested in this study, including the type VI secretion system, the Flp/Tad pilus and a two component system regulating the pilus, the SirB protein of unknown function and a genomic island containing a predicted lipoprotein transporter and a HopL1-like protein that is similar to the type III secretion system effector HopL1 in Pseudomonas syringae. This study provides novel information about the phylogeny and virulence of devastating plant pathogens that are present in Finland and worldwide. This information could be utilized in subsequent applied studies that could enhance plant health as an economically important part of potato production and industry.
Source: Työväentutkimus Vuosikirja
Author: Johanna Nykyri
Language: English
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W1544668849