Mitochondrial genome of Geomydoecus aurei, a pocket-gopher louse

Abstract

Parasitic lice demonstrate an unusual array of mitochondrial genome architectures and gene arrangements. We characterized the mitochondrial genome of Geomydoecus aurei, a chewing louse (Phthiraptera: Trichodectidae) found on pocket gophers (Rodentia: Geomyidae) using reads from both Illumina and Oxford Nanopore sequencing coupled with PCR, cloning, and Sanger sequencing to verify structure and arrangement for each chromosome. The genome consisted of 12 circular mitochondrial chromosomes ranging in size from 1,318 to 2,088 nucleotides (nt). Total genome size was 19,015 nt. All 37 genes typical of metazoans (2 rRNA genes, 22 tRNA genes, and 13 protein-coding genes) were present. An average of 26% of each chromosome was composed of non-gene sequences. Within the non-gene region of each chromosome, there was a 79-nt nucleotide sequence that was identical among chromosomes and a conserved sequence with secondary structure that was always followed by a poly-T region. We hypothesize that these regions may be important in the initiation of transcription and DNA replication, respectively. The G. aurei genome shares 8 derived gene clusters with other chewing lice of mammals, but in G. aurei, genes on several chromosomes are not contiguous.

Mitochondrial Genome Fragmentation Occurred Multiple Times Independently in Bird Lice of the Families Menoponidae and Laemobothriidae

“…The evidence available to date indicates that mt genome fragmentation occurred independently at least 14 times among parasitic lice (infraorder Phthiraptera): once in eutherian mammal lice in three parvorders (Anoplura, Rhynchophthirina, and Trichodectera) [16,20], four to five times in amblyceran lice ( [20], and the present study), and nine times in ischnoceran lice [20]. The independent evolution of fragmented mt genomes is also supported by the observations of the typical single-chromosome mt genomes in 16 amblyceran species from four different families (Boopiidae, Laemobothriidae, Menoponidae, and Ricinidae) ( [16,17,22,23], and the current study), in 10 ischnoceran species from 10 genera [16,18,21,41], but not in any species in Anoplura, Rhynchophthirina, or Trichodectera [4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Valuable Information for Resolving Phylogenetic Relationships at Different Taxonomic Levels Song et al [16] showed that mt genome fragmentation and minichromosomal characters united parasitic lice of eutherian mammals in three parvorders: Anoplura, Rhyn-chophthirina, and Trichodectera. All species in these three parvorders studied to date have fragmented mt genomes with a varying number of minichromosomes, from 9 to 20 in each species [4][5][6][7][8][9][10][11][12][13][14][15]17]. When only protein-coding and rRNA genes (these genes are more stable than tRNA genes in chromosomal locations) are considered, five minichromosomes, which contain cox1, nad4, nad5, rrnS, and rrnL, respectively, are in common among all eutherian mammal lice in these three parvorders, whereas other minichromosomes are variable [16].…”

“…Among parasitic lice, chewing lice are in four parvorders: Amblycera, Ischnocera, Rhynchophthirina, and Trichodectera, while sucking lice are in the parvorder Anoplura [ 3 ]. Fragmented mitochondrial (mt) genomes have been found in 21 species of Anoplura [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], one species of Rhynchophthirina [ 15 ], and five species of Trichodectera [ 16 , 17 ]. Each of these species has 9 to 20 minichromosomes, which are usually less than 4 kb in size.…”