Novel circular DNA viruses identified in Procordulia grayi and Xanthocnemis zealandica larvae using metagenomic approaches

Recent advances in sequencing and metagenomics have enabled the discovery of many novel single stranded DNA (ssDNA) viruses from various environments. We have previously demonstrated that adult dragonflies, as predatory insects, are useful indicators of ssDNA viruses in terrestrial ecosystems. Here we recover and characterise 13 viral genomes which represent 10 novel and diverse circular replication associated protein (Rep)-encoding single stranded (CRESS) DNA viruses (1628-2668 nt) from Procordulia grayi and Xanthocnemis zealandica dragonfly larvae collected from four high-country lakes in the South Island of New Zealand. The dragonfly larvae associated CRESS DNA viruses have different genome architectures, however, they all encode two major open reading frames (ORFs) which either have bidirectional or unidirectional arrangement. The 13 viral genomes have a conserved NAGTATTAC nonanucleotide motif and in their predicted Rep proteins we identified the rolling circle replication (RCR) motif 1, 2 and 3, as well as superfamily 3 (SF3) helicase motifs. Maximum likelihood phylogenetic and pairwise identity analysis of the Rep amino acid sequences reveal that the dragonfly larvae novel CRESS DNA viruses share <63% pairwise amino acid identity to the Reps of other CRESS DNA viruses whose complete genomes have been determined and available in public databases and that these viruses are novel. CRESS DNA viruses are circulating in larval dragonfly populations; however, we are unable to ascertain whether these viruses are infecting the larvae directly or are transient within dragonflies via their diet.