Fragmented mitochondrial genomes of the rat lice, Polyplax asiatica and Polyplax spinulosa: intra-genus variation in fragmentation pattern and a possible link between the extent of fragmentation and the length of life cycle.
BACKGROUND
Blood-sucking lice (suborder Anoplura) parasitize eutherian mammals with 67% of the 540 described species found on rodents. The five species of blood-sucking lice that infest humans and pigs have fragmented mitochondrial genomes and differ substantially in the extent of fragmentation. To understand whether, or not, any life-history factors are linked to such variation, we sequenced the mt genomes of Polyplax asiatica and Polyplax spinulosa, collected from the greater bandicoot rat, Bandicota indica, and the Asian house rat, Rattus tanezumi, respectively.


RESULTS
We identified all of the 37 mitochondrial genes common to animals in Polyplax asiatica and Polyplax spinulosa. The mitochondrial genes of these two rat lice are on 11 circular minichromosomes; each minichromosome is 2-4 kb long and has 2-7 genes. The two rat lice share the same pattern for the distribution of the protein-coding genes and ribosomal RNA genes over the minichromosomes, but differ in the pattern for the distribution of 8 of the 22 transfer RNA genes. The mitochondrial genomes of the Polyplax rat lice have 3.4 genes, on average, on each minichromosome and, thus, are less fragmented than those of the human lice (2.1 and 2.4 genes per minichromosome), but are more fragmented than those of the pig lice (4.1 genes per minichromosome).


CONCLUSIONS
Our results revealed distinct patterns of mitochondrial genome fragmentation within the genus Polyplax and, furthermore, indicated a possible inverse link between the extent of mitochondrial genome fragmentation and the length of life cycle of the blood-sucking lice.
Wen-Ge
WG
Dong
Simon
S
Song
Institute of Entomology, Guizhou University, and the Provincial Key Laboratory for Agricultural Pest Management in Mountainous Region, Guiyang 550025, China. daochaojin@126.com.
Dao-Chao
DC
Jin
Xian-Guo
XG
Guo
Renfu
R
Shao
D000818:Animals; D000854:Anoplura / Q000235:genetics* / Q000254:growth & development*; D001483:Base Sequence; D053938:DNA Fragmentation; D019143:Evolution, Molecular; D054629:Genome, Mitochondrial; D008018:Life Cycle Stages / Q000235:genetics*; D008928:Mitochondria / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D016415:Sequence Alignment; D020506:Untranslated Regions
D012335:RNA, Ribosomal; D020506:Untranslated Regions; D012343:RNA, Transfer