Molecular Ecology (2017) 26, 2092-2110

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Henrik H. De Fine Licht, Annette B. Jensen and Jørgen Eilenberg (2017)
Comparative transcriptomics reveal host-specific nucleotide variation in entomophthoralean fungi
Molecular Ecology 26 (7), 2092-2110
Abstract: Obligate parasites are under strong selection to increase exploitation of their host to survive while evading detection by host immune defences. This has often led to elaborate pathogen adaptations and extreme host specificity. Specialization on one host, however, often incurs a trade-off influencing the capacity to infect alternate hosts. Here, we investigate host adaptation in two morphologically indistinguishable and closely related obligate specialist insect-pathogenic fungi from the phylum Entomophthoromycota, Entomophthora muscae sensu stricto and E. muscae sensu lato, pathogens of houseflies (Musca domestica) and cabbage flies (Delia radicum), respectively. We compared single nucleotide polymorphisms within and between these two E. muscae species using 12 RNA-seq transcriptomes from five biological samples. All five isolates contained intra-isolate polymorphisms that segregate in 50:50 ratios, indicative of genetic duplication events or functional diploidy. Comparative analysis of dN/dS ratios between the multinucleate E. muscae s.str. and E. muscae s.l. revealed molecular signatures of positive selection in transcripts related to utilization of host lipids and the potential secretion of toxins that interfere with the host immune response. Phylogenetic comparison with the nonobligate generalist insect-pathogenic fungus Conidiobolus coronatus revealed a gene-family expansion of trehalase enzymes in E. muscae. The main sugar in insect haemolymph is trehalose, and efficient sugar utilization was probably important for the evolutionary transition to obligate insect pathogenicity in E. muscae. These results support the hypothesis that genetically based host specialization in specialist pathogens evolves in response to the challenge of using resources and dealing with the immune system of different hosts.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Jørgen Eilenberg, Annette Bruun Jensen

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
molecular biology - genes

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Delia radicum
Musca domestica
Entomophthora muscae (entomopathogen) Delia radicum
Entomophthora muscae (entomopathogen) Musca domestica