The Multipartite Mitochondrial Genome of Enteromyxum leei (Myxozoa): Eight Fast-Evolving Megacircles

Abstract

Myxozoans are a large group of poorly characterized cnidarian parasites. To gain further insight into their evolution, we sequenced the mitochondrial (mt) genome of Enteromyxum leei and reevaluate the mt genome structure of Kudoa iwatai. Although the typical animal mt genome is a compact, 13-25 kb, circular chromosome, the mt genome of E. leei was found to be fragmented into eight circular chromosomes of ∼23 kb, making it the largest described animal mt genome. Each chromosome was found to harbor a large noncoding region (∼15 kb), nearly identical between chromosomes. The protein coding genes show an unusually high rate of sequence evolution and possess little similarity to their cnidarian homologs. Only five protein coding genes could be identified and no tRNA genes. Surprisingly, the mt genome of K. iwatai was also found to be composed of two chromosomes. These observations confirm the remarkable plasticity of myxozoan mt genomes.

Linear Mitochondrial genome in Anthozoa (Cnidaria): A case study in Ceriantharia

“…Kayal et al 2015;Takeuchi et al 2015). In contrast, in the myxozoan Enteromyxum leei, the mitogenome is organized into eight circular chromosomes (Yahalomi et al 2017). This high within-lineage variation in genome architecture mirrors what we have discovered here in Ceriantharia.…”

“…Furthermore, our phylogenetic reconstruction based on the sequences within the mitochondrial genome supports Ceriantharia as an isolated branch within Anthozoa, rather than as a close ally of Medusozoa (Fig 3). This pattern of sequence affinity despite structural difference was also seen for the myxozoans Kudoa and Enteromyxum (Takeuchi et al 2015, Yahalomi et al 2017: phylogenetic analyses of sequences place these species within or sister to the Medusozoa although the structure of their genomes is unlike those of other medusozoans.…”

The joint evolution of the Myxozoa and their alternate hosts: A cnidarian recipe for success and vast biodiversity

“…Parasitic taxa are likely to have a faster rate of molecular evolution in order to win the "arms race" against their hosts (e.g., Bromham, Cowman, & Lanfear, 2013;Paterson et al, 2010). The rate heterogeneity across genes within the Myxozoa can be as high as that between myxozoans and other organisms (Hartigan et al, 2016; this study), and mitochondrial gene order and organization is highly variable (Takeuchi et al, 2015;Yahalomi et al, 2017), indicating a considerably accelerated rate of molecular evolution, possibly the fastest known among eukaryotes.…”

A novel fragmented mitochondrial genome in the protist pathogenToxoplasma gondiiand related tissue coccidia

“…However, increasing bodies of literature indicate that this structure is 39 not universal and that considerable evolution of both genome structure and gene content 40 has occurred in both protists and multicellular eukaryotes ; Gissi et al 41 of angiosperms ranges from 200 kb to 11 Mb in size and shows a huge variation in 48 structure, content, gene/DNA transfers and processes such as RNA editing (Gualberto and 49 Newton 2017; Petersen et al 2017). Mitochondrial genomes consisting of multiple 50 divergent circular molecules have been noted in the fungus Spizellomyces (Burger and 51 Lang 2003), Columbicola feather lice (Sweet et al 2019) and certain cnidarian parasites 52 (Yahalomi et al 2017). Among the protists, the kinetoplastid mtDNA (called kDNA) 53 consists of multiple gene-encoding maxi-circles and guide RNA encoding minicircles that 54 form a tight physical network, the kinetoplast (Morris et al 2001).…”