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Pectobacterium atrosepticum and Pectobacterium carotovorum Harbor Distinct, Independently Acquired Integrative and Conjugative Elements Encoding Coronafacic Acid that Enhance Virulence on Potato Stems.

Panda P, Vanga BR, Lu A, Fiers M, Fineran PC, Butler R, Armstrong K, Ronson CW, Pitman AR - Front Microbiol (2016)

Bottom Line: Much is known about the functions of the virulence determinants that ICEs harbor, but little is understood about the cryptic effects of ICEs on their host cell.As expected, deletion of HAI2 resulted in reduced blackleg symptoms in potato stems.Thus, the future spread of these ICEs via lateral gene transfer might contribute to an increase in the prevalence of blackleg-causing strains of P. carotovorum.

View Article: PubMed Central - PubMed

Affiliation: The Bio-Protection Research CentreLincoln, New Zealand; Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand.

ABSTRACT
Integrative and conjugative elements (ICEs) play a central role in the evolution of bacterial virulence, their transmission between bacteria often leading to the acquisition of virulence factors that alter host range or aggressiveness. Much is known about the functions of the virulence determinants that ICEs harbor, but little is understood about the cryptic effects of ICEs on their host cell. In this study, the importance of horizontally acquired island 2 (HAI2), an ICE in the genome of Pectobacterium atrosepticum SCRI1043, was studied using a strain in which the entire ICE had been removed by CRISPR-Cas-mediated genome editing. HAI2 encodes coronafacic acid, a virulence factor that enhances blackleg disease of potato stems caused by P. atrosepticum SCRI1043. As expected, deletion of HAI2 resulted in reduced blackleg symptoms in potato stems. A subsequent screen for HAI2-related ICEs in other strains of the Pectobacterium genus revealed their ubiquitous nature in P. atrosepticum. Yet, HAI2-related ICEs were only detected in the genomes of a few P. carotovorum strains. These strains were notable as blackleg causing strains belonging to two different subspecies of P. carotovorum. Sequence analysis of the ICEs in different strains of both P. atrosepticum and P. carotovorum confirmed that they were diverse and were present in different locations on the genomes of their bacterial host, suggesting that the cfa cluster was probably acquired independently on a number of occasions via chromosomal insertion of related ICEs. Excision assays also demonstrated that the ICEs in both P. atrosepticum and P. carotovorum are mobilized from the host chromosome. Thus, the future spread of these ICEs via lateral gene transfer might contribute to an increase in the prevalence of blackleg-causing strains of P. carotovorum.

No MeSH data available.


Related in: MedlinePlus

Deletion of HAI2 from Pectobacterium atrosepticum SCRI1043 reduces development of blackleg on potato stems. (A) Incidence of blackleg (% of plants with stem lesions) at each assessment for plants inoculated with either SCRI1043ΔHAI2 or the wild type. Each bacterium was inoculated into plants at either 104 or 106 cells per inoculation site. (B) Dot-histograms of lesion lengths on stems for each of 22 potato plants inoculated with either 104 or 106 cells per inoculation site of SCRI1043ΔHAI2 or the wild type. Measurements were taken every second day to 14 days post-inoculation.
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Figure 1: Deletion of HAI2 from Pectobacterium atrosepticum SCRI1043 reduces development of blackleg on potato stems. (A) Incidence of blackleg (% of plants with stem lesions) at each assessment for plants inoculated with either SCRI1043ΔHAI2 or the wild type. Each bacterium was inoculated into plants at either 104 or 106 cells per inoculation site. (B) Dot-histograms of lesion lengths on stems for each of 22 potato plants inoculated with either 104 or 106 cells per inoculation site of SCRI1043ΔHAI2 or the wild type. Measurements were taken every second day to 14 days post-inoculation.

Mentions: Plant infection assays were subsequently performed with the ‘ICE-less’ strain or the wild type using two different starting quantities of inoculum. In the wild type, blackleg incidence increased with greater inoculum (p = 0.018): 77.3% (95% confidence limits; 55.7, 90.2) of plants showing symptoms when inoculated with 106 cells versus 50.0% (30.2, 69.8) when inoculated with 104 cells per inoculation site (Figure 1A). The concentration of the inoculum also had a significant effect on the incidence of blackleg in plants inoculated with the ‘ICE-less’ strain, with blackleg incidence reaching 45.5% (95% confidence limits; 26.5, 65.9) in plants inoculated with 106 cells of the ICE-less strain but only 22.7% (9.8, 44.3) when inoculated with 104 cells after 14 days (Figure 1A).


Pectobacterium atrosepticum and Pectobacterium carotovorum Harbor Distinct, Independently Acquired Integrative and Conjugative Elements Encoding Coronafacic Acid that Enhance Virulence on Potato Stems.

Panda P, Vanga BR, Lu A, Fiers M, Fineran PC, Butler R, Armstrong K, Ronson CW, Pitman AR - Front Microbiol (2016)

Deletion of HAI2 from Pectobacterium atrosepticum SCRI1043 reduces development of blackleg on potato stems. (A) Incidence of blackleg (% of plants with stem lesions) at each assessment for plants inoculated with either SCRI1043ΔHAI2 or the wild type. Each bacterium was inoculated into plants at either 104 or 106 cells per inoculation site. (B) Dot-histograms of lesion lengths on stems for each of 22 potato plants inoculated with either 104 or 106 cells per inoculation site of SCRI1043ΔHAI2 or the wild type. Measurements were taken every second day to 14 days post-inoculation.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814525&req=5

Figure 1: Deletion of HAI2 from Pectobacterium atrosepticum SCRI1043 reduces development of blackleg on potato stems. (A) Incidence of blackleg (% of plants with stem lesions) at each assessment for plants inoculated with either SCRI1043ΔHAI2 or the wild type. Each bacterium was inoculated into plants at either 104 or 106 cells per inoculation site. (B) Dot-histograms of lesion lengths on stems for each of 22 potato plants inoculated with either 104 or 106 cells per inoculation site of SCRI1043ΔHAI2 or the wild type. Measurements were taken every second day to 14 days post-inoculation.
Mentions: Plant infection assays were subsequently performed with the ‘ICE-less’ strain or the wild type using two different starting quantities of inoculum. In the wild type, blackleg incidence increased with greater inoculum (p = 0.018): 77.3% (95% confidence limits; 55.7, 90.2) of plants showing symptoms when inoculated with 106 cells versus 50.0% (30.2, 69.8) when inoculated with 104 cells per inoculation site (Figure 1A). The concentration of the inoculum also had a significant effect on the incidence of blackleg in plants inoculated with the ‘ICE-less’ strain, with blackleg incidence reaching 45.5% (95% confidence limits; 26.5, 65.9) in plants inoculated with 106 cells of the ICE-less strain but only 22.7% (9.8, 44.3) when inoculated with 104 cells after 14 days (Figure 1A).

Bottom Line: Much is known about the functions of the virulence determinants that ICEs harbor, but little is understood about the cryptic effects of ICEs on their host cell.As expected, deletion of HAI2 resulted in reduced blackleg symptoms in potato stems.Thus, the future spread of these ICEs via lateral gene transfer might contribute to an increase in the prevalence of blackleg-causing strains of P. carotovorum.

View Article: PubMed Central - PubMed

Affiliation: The Bio-Protection Research CentreLincoln, New Zealand; Plant Pathology, The New Zealand Institute for Plant and Food Research LimitedLincoln, New Zealand.

ABSTRACT
Integrative and conjugative elements (ICEs) play a central role in the evolution of bacterial virulence, their transmission between bacteria often leading to the acquisition of virulence factors that alter host range or aggressiveness. Much is known about the functions of the virulence determinants that ICEs harbor, but little is understood about the cryptic effects of ICEs on their host cell. In this study, the importance of horizontally acquired island 2 (HAI2), an ICE in the genome of Pectobacterium atrosepticum SCRI1043, was studied using a strain in which the entire ICE had been removed by CRISPR-Cas-mediated genome editing. HAI2 encodes coronafacic acid, a virulence factor that enhances blackleg disease of potato stems caused by P. atrosepticum SCRI1043. As expected, deletion of HAI2 resulted in reduced blackleg symptoms in potato stems. A subsequent screen for HAI2-related ICEs in other strains of the Pectobacterium genus revealed their ubiquitous nature in P. atrosepticum. Yet, HAI2-related ICEs were only detected in the genomes of a few P. carotovorum strains. These strains were notable as blackleg causing strains belonging to two different subspecies of P. carotovorum. Sequence analysis of the ICEs in different strains of both P. atrosepticum and P. carotovorum confirmed that they were diverse and were present in different locations on the genomes of their bacterial host, suggesting that the cfa cluster was probably acquired independently on a number of occasions via chromosomal insertion of related ICEs. Excision assays also demonstrated that the ICEs in both P. atrosepticum and P. carotovorum are mobilized from the host chromosome. Thus, the future spread of these ICEs via lateral gene transfer might contribute to an increase in the prevalence of blackleg-causing strains of P. carotovorum.

No MeSH data available.


Related in: MedlinePlus