Genome report: sequencing of Helicoverpa- infecting Ophryocystis sp. confirms cryptic diversity and changes in gene content of Lepidoptera-infecting apicomplexan parasites

Abstract

Apicomplexan parasites of insects represent a largely unexplored branch of the tree of life. Their small size and lack of informative phenotypic traits can obscure their diversity and many lineage-specific adaptations to different host species. To better understand how these parasites have evolved, we have sequenced and annotated the genome of a neogregarine parasite of moths in the family Noctuidae, including Helicoverpa armigera. This parasite, which we term Helicoverpa-infecting Ophryocystis, has a tiny 8 Megabase genome with only 2,500 predicted protein-coding genes. Using phylogenomic methods, we placed it as the closest currently sequenced relative to Ophryocystis elektroscirrha and its sister lineage, both of which infect milkweed butterflies (Lepidoptera: Nymphalidae). We also explored the conservation of gene families, with a specific focus on the evolution of the ATPase gene family, as this is thought to be reduced in other Ophryocystis lineages. We found that our newly sequenced lineage also lacks any sodium pump ATPases, while all other types are conserved. Our results demonstrate the utility of applying modern genomic approaches to gaining insights into the evolution of insect-infecting Apicomplexa, but also shows that much remains to be discovered.