Engledow, A. S., Medrano, E. G., Mahenthiralingam, Eshwar ![]() |
Abstract
Burkholderia cenocepacia strain K56-2, a representative of the Burkholderia cepacia complex, is part of the epidemic and clinically problematic ET12 lineage. The strain produced plant tissue watersoaking (ptw) on onion tissue, which is a plant disease-associated trait. Using plasposon mutagenesis, mutants in the ptw phenotype were generated. The translated sequence of a disrupted gene (ptwD4) from a ptw-negative mutant showed homology to VirD4-like proteins. Analysis of the region proximal to the transfer gene homolog identified a gene cluster located on the 92-kb resident plasmid that showed homology to type IV secretion systems. The role of ptwD4, ptwC, ptwB4, and ptwB10 in the expression of ptw activity was determined by conducting site-directed mutagenesis. The ptw phenotype was not expressed by K56-2 derivatives with a disruption in ptwD4, ptwB4, or ptwB10 but was observed in a derivative with a disruption in ptwC. Complementation of ptw-negative K56-2 derivatives in trans resulted in complete restoration of the ptw phenotype. In addition, analysis of culture supernatants revealed that the putative ptw effector(s) was a secreted, heat-stable protein(s) that caused plasmolysis of plant protoplasts. A second chromosomally encoded type IV secretion system with complete homology to the VirB-VirD system was identified in K56-2. Site-directed mutagenesis of key secretory genes in the VirB-VirD system did not affect expression of the ptw phenotype. Our findings indicate that in strain K56-2, the plasmid-encoded Ptw type IV secretion system is responsible for the secretion of a plant cytotoxic protein(s).
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Biosciences |
Publisher: | American Society for Microbiology |
ISSN: | 0021-9193 |
Last Modified: | 27 Oct 2022 09:00 |
URI: | https://orca.cardiff.ac.uk/id/eprint/64070 |
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