Abstract
BackgroundMultipartite mitochondrial genomes are very rare in animals but have been found previously in two insect orders with highly rearranged genomes, the Phthiraptera (parasitic lice), and the Psocoptera (booklice/barklice).ResultsWe provide the first report of a multipartite mitochondrial genome architecture in a third order with highly rearranged genomes: Thysanoptera (thrips). We sequenced the complete mitochondrial genomes of two divergent members of the Scirtothrips dorsalis cryptic species complex. The East Asia 1 species has the single circular chromosome common to animals while the South Asia 1 species has a genome consisting of two circular chromosomes. The fragmented South Asia 1 genome exhibits extreme chromosome size asymmetry with the majority of genes on the large, 14.28 kb, chromosome and only nad6 and trnC on the 0.92 kb mini-circle chromosome. This genome also features paralogous control regions with high similarity suggesting a very recent origin of the nad6 mini-circle chromosome in the South Asia 1 cryptic species.ConclusionsThysanoptera, along with the other minor paraenopteran insect orders should be considered models for rapid mitochondrial genome evolution, including fragmentation. Continued use of these models will facilitate a greater understanding of recombination and other mitochondrial genome evolutionary processes across eukaryotes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1672-4) contains supplementary material, which is available to authorized users.
Highlights
Multipartite mitochondrial genomes are very rare in animals but have been found previously in two insect orders with highly rearranged genomes, the Phthiraptera, and the Psocoptera
Subsequent scaffolding of the next-generation sequencing (NGS) contigs of provisional mitochondrial origin yielded a completed circular mitochondrial chromosome for East Asia 1 (EA1), but we were unable to circularize the South Asia 1 (SA1) genome using NGS data and instead inferred a single large chromosome by placing two short gap fillers consisting of EA1 sequence into the inferred single SA1 chromosome prior to capillary sequencing validation
The sequence of this product was mitochondrial in origin, contained a control region and a trnS1 gene. These paralogs were highly similar (98.35 % and 100 % respectively) to those in the larger, but nad6 and trnC deficient, mitochondrial chromosome. This experiment simultaneously validated the existence of a second non-redundant mitochondrial chromosome in the SA1 cryptic species of S. dorsalis (Fig. 2) and confirmed the presence of all 37 mitochondrial genes in the SA1 genome
Summary
Multipartite mitochondrial genomes are very rare in animals but have been found previously in two insect orders with highly rearranged genomes, the Phthiraptera (parasitic lice), and the Psocoptera (booklice/barklice). Multipartite mitochondrial genomes are common among plants [1, 2], but are quite rare among animals, the majority of which possess a single, 10–35 kb circular chromosome [3]. Phthiraptera [4, 5] and Psocoptera [6] are the only two insect orders containing species with multipartite mitochondrial genomes. These orders, together with the Hemiptera and Thysanoptera, comprise the insect superorder Paraneoptera. The size and shape of thrips helps explain their significant representation on many invasive species lists and Dickey et al BMC Genomics (2015) 16:439
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