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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.

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Related in: MedlinePlus

Age of recombination blocks.(A) Age of the 675 recombination blocks (mutation rate of μ = 10−6) estimated using binomial mass function; (B) Boxplot of the median (plus first nation blocks and third quartile) log-age of recombination events in contigs. Only contigs with eight or more events are shown. There is no significant difference in age of events between contigs (GLM: F22, 233 = 1.06, p = 0.387).DOI:http://dx.doi.org/10.7554/eLife.04550.010
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fig5: Age of recombination blocks.(A) Age of the 675 recombination blocks (mutation rate of μ = 10−6) estimated using binomial mass function; (B) Boxplot of the median (plus first nation blocks and third quartile) log-age of recombination events in contigs. Only contigs with eight or more events are shown. There is no significant difference in age of events between contigs (GLM: F22, 233 = 1.06, p = 0.387).DOI:http://dx.doi.org/10.7554/eLife.04550.010

Mentions: Despite the fact that introgression between races is rare, it must have occurred multiple times between the ancestors of the three races given that the coalescence times varies markedly between the different blocks (Figure 5). Assuming a base mutation rate of µ = 10−8 per cell cycle, with 100 cell cycles per year (i.e., a combined mutation rate of 10−6 per year), analysis in the software HybRIDS show that the most recent introgression event has occurred circa 220 years ago, whilst the oldest event occurred almost 200,000 years ago. The mean age calculated across all introgression events equals 6237 (±12,594) years (Figure 5). (With a combined mutation rate of µ = 10−7 per base per year, the range in the age of introgression would span from 2200 to 2,000,000 years). Irrespective of the mutation rate, the principal finding is that genetic introgression amongst A. candida races is an ongoing evolutionary process occurring across a wide range of evolutionary times, and that it gives rise to mosaic genomes with the introgression blocks interspersed in the recipient genomic background.10.7554/eLife.04550.010Figure 5.Age of recombination blocks.


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)

Age of recombination blocks.(A) Age of the 675 recombination blocks (mutation rate of μ = 10−6) estimated using binomial mass function; (B) Boxplot of the median (plus first nation blocks and third quartile) log-age of recombination events in contigs. Only contigs with eight or more events are shown. There is no significant difference in age of events between contigs (GLM: F22, 233 = 1.06, p = 0.387).DOI:http://dx.doi.org/10.7554/eLife.04550.010
© Copyright Policy
Related In: Results  -  Collection

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

fig5: Age of recombination blocks.(A) Age of the 675 recombination blocks (mutation rate of μ = 10−6) estimated using binomial mass function; (B) Boxplot of the median (plus first nation blocks and third quartile) log-age of recombination events in contigs. Only contigs with eight or more events are shown. There is no significant difference in age of events between contigs (GLM: F22, 233 = 1.06, p = 0.387).DOI:http://dx.doi.org/10.7554/eLife.04550.010
Mentions: Despite the fact that introgression between races is rare, it must have occurred multiple times between the ancestors of the three races given that the coalescence times varies markedly between the different blocks (Figure 5). Assuming a base mutation rate of µ = 10−8 per cell cycle, with 100 cell cycles per year (i.e., a combined mutation rate of 10−6 per year), analysis in the software HybRIDS show that the most recent introgression event has occurred circa 220 years ago, whilst the oldest event occurred almost 200,000 years ago. The mean age calculated across all introgression events equals 6237 (±12,594) years (Figure 5). (With a combined mutation rate of µ = 10−7 per base per year, the range in the age of introgression would span from 2200 to 2,000,000 years). Irrespective of the mutation rate, the principal finding is that genetic introgression amongst A. candida races is an ongoing evolutionary process occurring across a wide range of evolutionary times, and that it gives rise to mosaic genomes with the introgression blocks interspersed in the recipient genomic background.10.7554/eLife.04550.010Figure 5.Age of recombination blocks.

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