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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

A nucleotide alignment of putative ICEs encoding coronafacic acid in strains of P. atrosepticum and P. carotovorum. The schematic representation drawn using Easyfig (Sullivan et al., 2011) shows pairwise alignments between PbN1_GI15 from P. carotovorum subsp. brasiliensis ICMP 19477, HAI2 from P. atrosepticum, SCRI1043, Pba1526_HAI2 from P. atrosepticum ICMP 1526 and PccUGC_HAI2 from P. carotovorum subsp. carotovorum UGC32. Orange arrows indicate annotated Coding Domain Sequences (CDSs). The locus tags for CDSs from the putative ICE in P. carotovorum subsp. brasiliensis ICMP 19477 are provided above the arrows, and their regions of nucleotide identity with CDSs from other putative ICEs are represented by gray shading. The genome coordinates for the ICEs in each strain are as follows: 910293 to 1008796 for PbN1_GI15, 590755 to 688630 for HAI2, 958243 to 1055429 for Pba1526_HAI2 and 591326 to 692291 for PccUGC_HAI2.
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Figure 4: A nucleotide alignment of putative ICEs encoding coronafacic acid in strains of P. atrosepticum and P. carotovorum. The schematic representation drawn using Easyfig (Sullivan et al., 2011) shows pairwise alignments between PbN1_GI15 from P. carotovorum subsp. brasiliensis ICMP 19477, HAI2 from P. atrosepticum, SCRI1043, Pba1526_HAI2 from P. atrosepticum ICMP 1526 and PccUGC_HAI2 from P. carotovorum subsp. carotovorum UGC32. Orange arrows indicate annotated Coding Domain Sequences (CDSs). The locus tags for CDSs from the putative ICE in P. carotovorum subsp. brasiliensis ICMP 19477 are provided above the arrows, and their regions of nucleotide identity with CDSs from other putative ICEs are represented by gray shading. The genome coordinates for the ICEs in each strain are as follows: 910293 to 1008796 for PbN1_GI15, 590755 to 688630 for HAI2, 958243 to 1055429 for Pba1526_HAI2 and 591326 to 692291 for PccUGC_HAI2.

Mentions: As in P. atrosepticum SCRI1043, the cfa biosynthetic clusters in P. atrosepticum ICMP 1526, P. carotovorum subsp. brasiliensis ICMP 19477 and P. carotovorum subsp. carotovorum UGC32 were located on putative ICEs. As predicted from excision assays, the ICE (named Pba1526_HAI2) in P. atrosepticum ICMP 1526 had high sequence identity (99%) to HAI2 (Figure 4), but was inserted into a second phe-tRNA gene located adjacent to speC (locus tag: ECA0967). Pba1526_HAI2 was 97,216 bp, contained 97 putative CDSs (Supplementary Table S2) and was delineated by 49-bp direct repeat sequences attL and attR. Gene organization on Pba1526_HAI2 was almost identical to that on HAI2 (Figure 4; Supplementary Table S2). Synteny was lost in only one region, notably, within and immediately adjacent to pilV, which encodes a component of the type IV pilus involved in conjugation. The pilV shufflon on other mobile elements acts as a biological switch, selecting one of seven C-terminal segments of the pilV gene that confer recipient specificity during conjugation (Komano et al., 1987).


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)

A nucleotide alignment of putative ICEs encoding coronafacic acid in strains of P. atrosepticum and P. carotovorum. The schematic representation drawn using Easyfig (Sullivan et al., 2011) shows pairwise alignments between PbN1_GI15 from P. carotovorum subsp. brasiliensis ICMP 19477, HAI2 from P. atrosepticum, SCRI1043, Pba1526_HAI2 from P. atrosepticum ICMP 1526 and PccUGC_HAI2 from P. carotovorum subsp. carotovorum UGC32. Orange arrows indicate annotated Coding Domain Sequences (CDSs). The locus tags for CDSs from the putative ICE in P. carotovorum subsp. brasiliensis ICMP 19477 are provided above the arrows, and their regions of nucleotide identity with CDSs from other putative ICEs are represented by gray shading. The genome coordinates for the ICEs in each strain are as follows: 910293 to 1008796 for PbN1_GI15, 590755 to 688630 for HAI2, 958243 to 1055429 for Pba1526_HAI2 and 591326 to 692291 for PccUGC_HAI2.
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Related In: Results  -  Collection

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

Figure 4: A nucleotide alignment of putative ICEs encoding coronafacic acid in strains of P. atrosepticum and P. carotovorum. The schematic representation drawn using Easyfig (Sullivan et al., 2011) shows pairwise alignments between PbN1_GI15 from P. carotovorum subsp. brasiliensis ICMP 19477, HAI2 from P. atrosepticum, SCRI1043, Pba1526_HAI2 from P. atrosepticum ICMP 1526 and PccUGC_HAI2 from P. carotovorum subsp. carotovorum UGC32. Orange arrows indicate annotated Coding Domain Sequences (CDSs). The locus tags for CDSs from the putative ICE in P. carotovorum subsp. brasiliensis ICMP 19477 are provided above the arrows, and their regions of nucleotide identity with CDSs from other putative ICEs are represented by gray shading. The genome coordinates for the ICEs in each strain are as follows: 910293 to 1008796 for PbN1_GI15, 590755 to 688630 for HAI2, 958243 to 1055429 for Pba1526_HAI2 and 591326 to 692291 for PccUGC_HAI2.
Mentions: As in P. atrosepticum SCRI1043, the cfa biosynthetic clusters in P. atrosepticum ICMP 1526, P. carotovorum subsp. brasiliensis ICMP 19477 and P. carotovorum subsp. carotovorum UGC32 were located on putative ICEs. As predicted from excision assays, the ICE (named Pba1526_HAI2) in P. atrosepticum ICMP 1526 had high sequence identity (99%) to HAI2 (Figure 4), but was inserted into a second phe-tRNA gene located adjacent to speC (locus tag: ECA0967). Pba1526_HAI2 was 97,216 bp, contained 97 putative CDSs (Supplementary Table S2) and was delineated by 49-bp direct repeat sequences attL and attR. Gene organization on Pba1526_HAI2 was almost identical to that on HAI2 (Figure 4; Supplementary Table S2). Synteny was lost in only one region, notably, within and immediately adjacent to pilV, which encodes a component of the type IV pilus involved in conjugation. The pilV shufflon on other mobile elements acts as a biological switch, selecting one of seven C-terminal segments of the pilV gene that confer recipient specificity during conjugation (Komano et al., 1987).

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