Evolution of the Mitochondrial Genomes of Gall Midges (Diptera: Cecidomyiidae): Rearrangement and Severe Truncation of tRNA Genes

Abstract

We determined the complete mitochondrial genome sequences of two species of gall midges (Diptera: Cecidomyiidae), as well as partial sequence from a third cecidomyiid and a species from a related family, the Sciaridae. The sciarid sequence has a number of rearrangements of tRNA genes, relative to other dipterans, but is otherwise unremarkable. In contrast, the cecidomyiid genomes possess a number of very unusual features. First, the two complete sequences are very small compared with other dipteran mitochondrial genomes. The genome of Mayetiola destructor is only 14,759 bp while that of Rhopalomyia pomum is only 14,503 bp, comparable with genome sizes observed in some arachnids. Second, all three cecidomyiid species have very high A + T content—more than 83% for the coding region. Third, all three cecidomyiid species possess a number of rearrangements of tRNA genes, including variations within the family. Fourth, the most extraordinary feature of cecidomyiids examined in this study is an extreme truncation of all tRNA genes, including the loss of TΨC arms and apparent absence of the 3′ part of the aminoacyl stems.The truncated tRNA genes of cecidomyiids are very similar to those previously reported for spiders and appear to represent a second, independent origin of these structural features. It is likely that they are made functional through RNA editing, perhaps using the 5′ end of the aminoacyl stem as a template for the construction of the required 3′ end.

The Complete Nucleotide Sequence of the Mitochondrial Genome of Bactrocera minax (Diptera: Tephritidae)

“…capitata ) but is still well within the range of other insect mitogenomes (14,503 bp in Rhopalomyia pomum [42] to 19517 bp in Drosophila melanogaster [11]). The gene content is typical of metazoan mitogenomes, with 13 PCGs ( cox1 - 3 , cob , nad1 - 6 , nad4l , atp6 and atp8 ), 22 tRNAs and two genes for ribosomal RNA subunits ( rrnS and rrnL ).…”

The complete mitochondrial genome of Pauropus longiramus (Myriapoda: Pauropoda): Implications on early diversification of the myriapods revealed from comparative analysis

“…Alternatively, when excessive overlaps occur between tRNAs, such as trnS1 and trnN, excisions at different points may yield one or other functional tRNA in a mutually exclusive manner (Qiu et al, 2005). Previous studies have shown that all of the tRNA genes are truncated and must be the end result of a long evolutionary process (Beckenbach and Joy, 2009;Lavrov et al, 2000a;Boore, 2004, 2008;Qiu et al, 2005;Segovia et al, 2011). Our study provides the first example where only some of the tRNAs are truncated.…”

“…Pauropus is the first example of a mitochondrial genome with multiple intergenic overlaps and reveals a strategy for arthropods to effectively compact mitochondrial genome size by overlapping tRNA genes with neighbor genes (Supplementary Fig. S2), instead of only truncating tRNAs through losses of the T-arm and/ or D-arm as is found in chelicerate lineages (Lavrov et al, 2000a;Boore, 2004, 2008;Qiu et al, 2005), gall midges (Beckenbach and Joy, 2009), and velvet worms (Segovia et al, 2011).…”

The Mitochondrial Genome of Elodia flavipalpis Aldrich (Diptera: Tachinidae) and the Evolutionary Timescale of Tachinid Flies

“…Gene order is typically conserved in brachyceran flies, except for a few species in which additional tRNAs have been detected in the control region ( Liriomyza trifolii , Chrysomya spp., and Cydistomyia duplonotata ), and Dermatobia hominis , in which an additional tRNA Val is found on the minor strand. In contrast, there is an elevated number of tRNA rearrangements in nematoceran flies [13], [14], [20], [21].…”