Host manipulation by oak gall wasps: Insights from evolutionary signatures in the gall-wasp genome

• The oak gall-wasps (Cynipidae: Cynipini) make some of the most complex plant galls found in nature. The shape of the outer gall varies spectacularly among species, and is characterised by traits that appear to have evolved to defend the larva or larvae inside in an intense evolutionary arms race with predators and parasitoids. It is still unclear how the oak gall-wasps achieve this unusual level of host manipulation. Here, we take a comparative genomic approach to gain some insight into the underlying mechanisms, assuming that the arms race should result in unusually rapid evolution in the proteins involved. Specifically, we compared genomes of Cynipini species making complex and diverse outer galls to those of related lineages making simple galls. We analysed over 5,000 orthologous genes using the recent Bayescode tool, which controls for the background levels of evolution in the genes and lineages involved using a whole-genome approach. We then used gene set enrichment analysis to identify which Gene Ontology terms were more often associated with genes that had an unusually high rate of nonsynonymous evolution in the complex gallers. The complex gallers did not have an elevated number of such genes. However, the genes that had elevated rates in complex gallers were associated with biological-process gene ontology terms related to the formation of the egg follicle and to cell movement, suggesting that these genes may play a role in the formation of complex outer galls, and that they would be interesting target genes for experimental studies.

Ämnesord

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

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