Patterns of molecular evolution of RNAi genes in social and socially parasitic bumblebees.
The high frequency of interactions amongst closely related individuals in social insect colonies enhances pathogen transmission. Group-mediated behavior supporting immune defenses tends to decrease selection acting on immune genes. Along with low effective population sizes this might result in relaxed constraint and rapid evolution of immune system genes. Here, we show that antiviral siRNA genes show high rates of molecular evolution with argonaute 2, armitage and maelstrom evolving faster in social bumblebees compared to their socially parasitic cuckoo bumblebees that lack a worker caste. RNAi genes show frequent positive selection at the codon level additionally supported by the occurrence of parallel evolution. Their evolutionary rate is linked to their pathway specific position with genes directly interacting with viruses showing the highest rates of molecular evolution. We suggest that higher pathogen load in social insects indeed drives the molecular evolution of immune genes including antiviral siRNA, if not compensated by behavior.
Institute of Biology, Molecular Ecology, Martin-Luther University Halle-Wittenberg, Hoher Weg 4, 06099 Halle (Saale), Germany.
Sophie
S
Helbing
Institute of Biology, Molecular Ecology, Martin-Luther University Halle-Wittenberg, Hoher Weg 4, 06099 Halle (Saale), Germany; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany. Electronic address: lattorff@zoologie.uni-halle.de.
H Michael G
HM
Lattorff
D000818:Animals; D060565:Argonaute Proteins / Q000235:genetics / Q000276:immunology; D003062:Codon; D019143:Evolution, Molecular; D005260:Female; D007113:Immunity, Innate; D019476:Insect Proteins / Q000235:genetics* / Q000276:immunology; D008297:Male; D010802:Phylogeny; D011156:Population Density; D020365:RNA Helicases / Q000235:genetics / Q000276:immunology; D034622:RNA Interference; D012641:Selection, Genetic; D012919:Social Behavior; D014863:Wasps / Q000145:classification / Q000235:genetics* / Q000276:immunology / Q000821:virology
D060565:Argonaute Proteins; D003062:Codon; D019476:Insect Proteins; D020365:RNA Helicases
Bombus; Cuckoo bumblebee; Parallel evolution; Positive selection; Social insects