Circulating miRNAome of avian influenza-infected ruddy turnstones Arenaria interpres

MicroRNAs (miRNAs) are highly conserved small noncoding RNAs that regulate gene expression post-transcriptionally. Circulating miRNAs – miRNAs that have been released from cells and circulate in the bloodstream – are relatively stable and interesting molecules for wildlife research, where they may form a proxy for gene expression as a function of the animal's state under a variety of environmental challenges. Aiming at providing initial baseline data on the circulating miRNAome in avian wildlife, we assessed the miRNA profiles of wild ruddy turnstones Arenaria interpres on their Australian non-breeding grounds. The ruddy turnstone is a long-distant migrant and a significant reservoir species for low pathogenic avian influenza virus (LPAIV). We therefore investigated both LPAIV-infected and uninfected individuals for their specific miRNA profiles to potentially elucidate the species' molecular mechanisms underlying its response to LPAIV infection. De novo miRNA characterisation in the ruddy turnstone genome identified 161 conserved and two novel, bird-specific miRNAs, with liver-enriched miRNA-122 being the most abundant. Z chromosome-linked miR-2954-3p was significantly more abundant in serum from males (ZZ) than from females (ZW). Furthermore, we found a sex- and age-associated effect of LPAIV infection on miRNA abundance in serum samples, including one novel miRNA. This circulating miRNA signature may reflect sex- and age-specific differences in the host response, indicating that circulating miRNAs could serve as a valuable non-destructive analytical tool for enhancing our understanding of avian infections in a wildlife context and should be explored further.