DNA methylation and aging variation of a malaria-infected songbird
: Epigenetic variation is a major source of plasticity in response to internal and external stimuli. DNA methylation (DNAm) is one mechanism that can contribute to both conditional plasticity, following an event such as a parasitic infection, and developmental plasticity, associated with aging. While conditional plasticity can impact host susceptibility to a parasitic infection, many of the specific DNAm variations are not yet described. Similarly, while novel epigenetic clocks (EC) are being developed, only a few EC are available for wild organisms. This study applied reduced representation bisulfite sequencing (RRBS) to measure DNAm patterns of wild Dark-eyed Juncos (Junco hyemalis). We compare DNAm in birds with malaria (Plasmodium relictum GRW04) infections, develop an EC clock, and compare aging in infected and non-infected birds. When comparing infected birds, six regions were consistently differentially methylated, including one region upstream of an immune response-related gene. Based on our EC, we found 18 genomic sites that accurately predicted age. While malaria infections were previously reported to accelerate telomere shortening, no difference was observed using our EC. This study provides new insight into the association between epigenetic changes, developmental plasticity and conditional plasticity in wild birds, and is one of the first studies to link parasite infection and epigenetic aging in a wild passerine.