pFiD188, the Linear Virulence Plasmid of Rhodococcus fascians D188

Abstract

Rhodococcus fascians is currently the only phytopathogen of which the virulence genes occur on a linear plasmid. To get insight into the origin of this replicon and into the virulence strategy of this broad-spectrum phytopathogen, the sequence of the linear plasmid of strain D188, pFiD188, was determined. Analysis of the 198,917 bp revealed four syntenic regions with linear plasmids of R. erythropolis, R. jostii, and R. opacus, suggesting a common origin of these replicons. Mutational analysis of pFi_086 and pFi_102, similar to cutinases and type IV peptidases, respectively, showed that conserved region R2 was involved in plasmid dispersal and pointed toward a novel function for actinobacterial cutinases in conjugation. Additionally, pFiD188 had three regions that were unique for R. fascians. Functional analysis of the stk and nrp loci of regions U2 and U3, respectively, indicated that their role in symptom development was limited compared with that of the previously identified fas, att, and hyp virulence loci situated in region U1. Thus, pFiD188 is a typical rhodococcal linear plasmid with a composite structure that encodes core functions involved in plasmid maintenance and accessory functions, some possibly acquired through horizontal gene transfer, implicated in virulence and the interaction with the host.

An Invertron-Like Linear Plasmid Mediates Intracellular Survival and Virulence in Bovine Isolates of Rhodococcus equi

“…3A), and the presence of telomeric invertron-like terminal inverted repeats (TIRs) with multiple palindromic secondary structures (Fig. 4) (43)(44)(45). The TIR sequences of pVAPN are 569 bp long and 99% identical.…”

“…Rhodococcus species characteristically possess large plasmids, circular or linear if Ͼ100 kb in size (46). These plasmids consist of a vertically evolving backbone, encoding plasmid maintenance and conjugal transfer functions, and a horizontally acquired variable region (VR) providing specific niche-adaptive properties to the host bacterium (24,37,44,45,47). The housekeeping backbone of pVAPN is unrelated to that of the circular pVAPA/B (equine/porcine-type) R. equi virulence plasmids.…”

“…In phages that infect mycolata, they form part of the LysB lipolytic enzyme complement, thought to aid in the breakdown of the lipid-rich envelope during phage penetration or lytic egress (59). Recently, a cutinase from the R. fascians pFiD188 linear virulence plasmid was shown to be required for efficient conjugation, probably by facilitating the penetration of the DNA translocation complex in the rhodococcal cell envelope (45).…”

“…Interestingly, in contrast to the circular pVAPA/B plasmids (and pREC1), pVAPN (and pNSL1) does not encode the ParB component of the ParAB replicon segregation system (60). The lack of a parB gene appears to be a hallmark of the Յ400-kb rhodococcal linear extrachromosomal replicons, as exemplified by pREL1 or pBD2 from R. erythropolis (44), pRHL2 and pRHL3 from R. jostii (37), or pFiD188 from R. fascians (45).…”

Analysis of Genome Sequences from Plant Pathogenic Rhodococcus Reveals Genetic Novelties in Virulence Loci

“…Phytopathogenicity of R. fascians D188 requires three virulence loci clustered on the conjugative linear plasmid, pFiD188 [14]–[19]. The fasA-F operon is the primary virulence operon and is implicated in the synthesis and modification of cytokinins, a class of plant growth regulating hormones (Fig.…”