Open AccessThe ESX /type VII secretion system modulates development, but not virulence, of the plant pathogen S treptomyces scabies
Author(s) -
Fyans Joanna K.,
Bignell Dawn,
Loria Rosemary,
Toth Ian,
Palmer Tracy
Publication year - 2013
Publication title -
molecular plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.945
H-Index - 103
eISSN - 1364-3703
pISSN - 1464-6722
DOI - 10.1111/j.1364-3703.2012.00835.x
Subject(s) - virulence , secretion , pathogen , microbiology and biotechnology , biology , gene , biochemistry
Summary S treptomyces scabies is a model organism for the investigation of plant–microbe interactions in G ram‐positive bacteria. Here, we investigate the type VII protein secretion system ( T 7 SS ) in S . scabies ; the T 7 SS is required for the virulence of other G ram‐positive bacteria, including M ycobacterium tuberculosis and S taphylococcus aureus . The hallmarks of a functional T 7 SS are an E cc C protein that forms an essential component of the secretion apparatus and two small, sequence‐related substrate proteins, E sx A and E sx B . A putative transmembrane protein, E cc D , may also be associated with T7S in Actinobacteria. In this study, we constructed strains of the plant pathogen S . scabies carrying marked mutations in genes coding for E cc C , E cc D , E sx A and E sx B . Unexpectedly, we showed that all four mutant strains retain full virulence towards several plant hosts. However, disruption of the esx A or esx B , but not ecc C or ecc D , genes affects S . scabies development, including a delay in sporulation, abnormal spore chains and resistance to lysis by the S treptomyces ‐specific phage ϕ C 31. We further showed that these phenotypes are specific to the loss of the T 7 SS substrate proteins E sx A and E sx B , and are not observed when components of the T 7 SS secretion machinery are lacking. Taken together, these results imply an unexpected intracellular role for E sx A and E sx B .