Limits...
Evidence for suppression of immunity as a driver for genomic introgressions and host range expansion in races of Albugo candida, a generalist parasite.

McMullan M, Gardiner A, Bailey K, Kemen E, Ward BJ, Cevik V, Robert-Seilaniantz A, Schultz-Larsen T, Balmuth A, Holub E, van Oosterhout C, Jones JD - Elife (2015)

Bottom Line: Despite this divergence, their genomes are mosaic-like, with ∼25% being introgressed from other races.This facilitates introgression and the exchange of effector repertoires, and may enable the evolution of novel races that can undergo clonal population expansion on new hosts.We discuss recent studies on hybridization in other eukaryotes such as yeast, Heliconius butterflies, Darwin's finches, sunflowers and cichlid fishes, and the implications of introgression for pathogen evolution in an agro-ecological environment.

View Article: PubMed Central - PubMed

Affiliation: The Sainsbury Laboratory, Norwich, United Kingdom.

ABSTRACT
How generalist parasites with wide host ranges can evolve is a central question in parasite evolution. Albugo candida is an obligate biotrophic parasite that consists of many physiological races that each specialize on distinct Brassicaceae host species. By analyzing genome sequence assemblies of five isolates, we show they represent three races that are genetically diverged by ∼1%. Despite this divergence, their genomes are mosaic-like, with ∼25% being introgressed from other races. Sequential infection experiments show that infection by adapted races enables subsequent infection of hosts by normally non-infecting races. This facilitates introgression and the exchange of effector repertoires, and may enable the evolution of novel races that can undergo clonal population expansion on new hosts. We discuss recent studies on hybridization in other eukaryotes such as yeast, Heliconius butterflies, Darwin's finches, sunflowers and cichlid fishes, and the implications of introgression for pathogen evolution in an agro-ecological environment.

Show MeSH

Related in: MedlinePlus

Nucleotide polymorphism within and between A. candida isolates.Mean (±5–95%CI) polymorphism expressed as the percentage observed heterozygote sites (solid symbols) and percentage nucleotide divergence (open symbols) at contig 1. Confidence intervals were calculated using a bootstrap of contig 1 after removal of indels. Isolates infecting the same host plant (i.e., AcBoT-AcBoL and AcEm2- AcNc2) show little nucleotide divergence, which indicates that they are genotypically almost identical (i.e., diverged by less than 0.05%). Nevertheless, the Brassica oleracea infecting race (AcBoT and AcBoL) possess a relatively high heterozygosity compared to the isolates of the Arabidopsis thaliana infecting race. Moreover, most of this heterozygous polymorphism is shared (low nucleotide divergence) and presence of the majority of heterozygous sites is consistent with clonal reproduction.DOI:http://dx.doi.org/10.7554/eLife.04550.008
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4384639&req=5

fig3: Nucleotide polymorphism within and between A. candida isolates.Mean (±5–95%CI) polymorphism expressed as the percentage observed heterozygote sites (solid symbols) and percentage nucleotide divergence (open symbols) at contig 1. Confidence intervals were calculated using a bootstrap of contig 1 after removal of indels. Isolates infecting the same host plant (i.e., AcBoT-AcBoL and AcEm2- AcNc2) show little nucleotide divergence, which indicates that they are genotypically almost identical (i.e., diverged by less than 0.05%). Nevertheless, the Brassica oleracea infecting race (AcBoT and AcBoL) possess a relatively high heterozygosity compared to the isolates of the Arabidopsis thaliana infecting race. Moreover, most of this heterozygous polymorphism is shared (low nucleotide divergence) and presence of the majority of heterozygous sites is consistent with clonal reproduction.DOI:http://dx.doi.org/10.7554/eLife.04550.008

Mentions: The overall mean level of nucleotide identity in the homologous genomic regions amongst races is ∼99% (Figure 2B). We verified 25 polymorphic genomic regions by Sanger sequencing (Supplementary file 3). We used the longest of all contigs from AcNc2, ‘contig 1’ (398,508 bp), to compare the levels of divergence between races vs the number of heterozygous positions within each race. An extremely low proportion of sites (0.03% and 0.01%) on ‘contig 1’ are heterozygous within AcNc2, AcEm2 and Ac2V races, respectively (Figure 3). Races AcBoT and AcBoL are more heterozygous than Ac2V and AcNc2, with 0.65% of nucleotide positions in ‘contig 1’ being heterozygous in AcBoT (Figure 3). Importantly, >97% of all heterozygous positions are shared in AcBoL and AcBoT (see below). In between-race comparisons, ∼1.0% of nucleotide positions on ‘contig 1’ have diverged between AcBoT, Ac2V and AcNc2.10.7554/eLife.04550.008Figure 3.Nucleotide polymorphism within and between A. candida isolates.


Evidence for suppression of immunity as a driver for genomic introgressions and host range expansion in races of Albugo candida, a generalist parasite.

McMullan M, Gardiner A, Bailey K, Kemen E, Ward BJ, Cevik V, Robert-Seilaniantz A, Schultz-Larsen T, Balmuth A, Holub E, van Oosterhout C, Jones JD - Elife (2015)

Nucleotide polymorphism within and between A. candida isolates.Mean (±5–95%CI) polymorphism expressed as the percentage observed heterozygote sites (solid symbols) and percentage nucleotide divergence (open symbols) at contig 1. Confidence intervals were calculated using a bootstrap of contig 1 after removal of indels. Isolates infecting the same host plant (i.e., AcBoT-AcBoL and AcEm2- AcNc2) show little nucleotide divergence, which indicates that they are genotypically almost identical (i.e., diverged by less than 0.05%). Nevertheless, the Brassica oleracea infecting race (AcBoT and AcBoL) possess a relatively high heterozygosity compared to the isolates of the Arabidopsis thaliana infecting race. Moreover, most of this heterozygous polymorphism is shared (low nucleotide divergence) and presence of the majority of heterozygous sites is consistent with clonal reproduction.DOI:http://dx.doi.org/10.7554/eLife.04550.008
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384639&req=5

fig3: Nucleotide polymorphism within and between A. candida isolates.Mean (±5–95%CI) polymorphism expressed as the percentage observed heterozygote sites (solid symbols) and percentage nucleotide divergence (open symbols) at contig 1. Confidence intervals were calculated using a bootstrap of contig 1 after removal of indels. Isolates infecting the same host plant (i.e., AcBoT-AcBoL and AcEm2- AcNc2) show little nucleotide divergence, which indicates that they are genotypically almost identical (i.e., diverged by less than 0.05%). Nevertheless, the Brassica oleracea infecting race (AcBoT and AcBoL) possess a relatively high heterozygosity compared to the isolates of the Arabidopsis thaliana infecting race. Moreover, most of this heterozygous polymorphism is shared (low nucleotide divergence) and presence of the majority of heterozygous sites is consistent with clonal reproduction.DOI:http://dx.doi.org/10.7554/eLife.04550.008
Mentions: The overall mean level of nucleotide identity in the homologous genomic regions amongst races is ∼99% (Figure 2B). We verified 25 polymorphic genomic regions by Sanger sequencing (Supplementary file 3). We used the longest of all contigs from AcNc2, ‘contig 1’ (398,508 bp), to compare the levels of divergence between races vs the number of heterozygous positions within each race. An extremely low proportion of sites (0.03% and 0.01%) on ‘contig 1’ are heterozygous within AcNc2, AcEm2 and Ac2V races, respectively (Figure 3). Races AcBoT and AcBoL are more heterozygous than Ac2V and AcNc2, with 0.65% of nucleotide positions in ‘contig 1’ being heterozygous in AcBoT (Figure 3). Importantly, >97% of all heterozygous positions are shared in AcBoL and AcBoT (see below). In between-race comparisons, ∼1.0% of nucleotide positions on ‘contig 1’ have diverged between AcBoT, Ac2V and AcNc2.10.7554/eLife.04550.008Figure 3.Nucleotide polymorphism within and between A. candida isolates.

Bottom Line: Despite this divergence, their genomes are mosaic-like, with ∼25% being introgressed from other races.This facilitates introgression and the exchange of effector repertoires, and may enable the evolution of novel races that can undergo clonal population expansion on new hosts.We discuss recent studies on hybridization in other eukaryotes such as yeast, Heliconius butterflies, Darwin's finches, sunflowers and cichlid fishes, and the implications of introgression for pathogen evolution in an agro-ecological environment.

View Article: PubMed Central - PubMed

Affiliation: The Sainsbury Laboratory, Norwich, United Kingdom.

ABSTRACT
How generalist parasites with wide host ranges can evolve is a central question in parasite evolution. Albugo candida is an obligate biotrophic parasite that consists of many physiological races that each specialize on distinct Brassicaceae host species. By analyzing genome sequence assemblies of five isolates, we show they represent three races that are genetically diverged by ∼1%. Despite this divergence, their genomes are mosaic-like, with ∼25% being introgressed from other races. Sequential infection experiments show that infection by adapted races enables subsequent infection of hosts by normally non-infecting races. This facilitates introgression and the exchange of effector repertoires, and may enable the evolution of novel races that can undergo clonal population expansion on new hosts. We discuss recent studies on hybridization in other eukaryotes such as yeast, Heliconius butterflies, Darwin's finches, sunflowers and cichlid fishes, and the implications of introgression for pathogen evolution in an agro-ecological environment.

Show MeSH
Related in: MedlinePlus