The Complete Mitochondrial Genome Sequence of the Spider Habronattus oregonensis Reveals Rearranged and Extremely Truncated tRNAs

Abstract

We sequenced the entire mitochondrial genome of the jumping spider Habronattus oregonensis of the arachnid order Araneae (Arthropoda: Chelicerata). A number of unusual features distinguish this genome from other chelicerate and arthropod mitochondrial genomes. Most of the transfer RNA (tRNA) gene sequences are greatly reduced in size and cannot be folded into typical cloverleaf-shaped secondary structures. At least nine of the tRNA sequences lack the potential to form TPsiC arm stem pairings and instead are inferred to have TV-replacement loops. Furthermore, sequences that could encode the 3' aminoacyl acceptor stems in at least 10 tRNAs appear to be lacking, because fully paired acceptor stems are not possible and because the downstream sequences instead encode adjacent genes. Hence, these appear to be among the smallest known tRNA genes. We postulate that an RNA editing mechanism must exist to restore the 3' aminoacyl acceptor stems to allow the tRNAs to function. At least seven tRNAs are rearranged with respect to the chelicerate Limulus polyphemus, although the arrangement of the protein-coding genes is identical. Most mitochondrial protein-coding genes of H. oregonensis have ATN as initiation codons, as commonly found in arthropod mtDNAs, but cytochrome oxidase subunits 2 and 3 genes apparently use TTG as an initiation codon. Finally, many of the gene sequences overlap one another and are truncated. This 14,381-bp genome, the first mitochondrial genome of a spider yet sequenced, is one of the smallest arthropod mitochondrial genomes known. We suggest that posttranscriptional RNA editing can likely maintain function of the tRNAs, while permitting the accumulation of mutations that would otherwise be deleterious. Such mechanisms may have allowed for the minimization of the spider mitochondrial genome.

The complete mitochondrial genome of Euthrix laeta (Lepidoptera: Lasiocampidae)

“…The abnormal start codon in the COI gene was found presently in all mitochondrial genomes of Lepidoptera (Lee et al 2006). Three PCGs (COI, COII and ND4) used incomplete stop codon T, which was commonly reported in other invertebrates (Masta & Boore 2004). The other 10 PCGs stopped with complete stop codon TAA.…”

Complete mitochondrial genome of a leaf-mining beetle, Agonita chinensis Weise (Coleoptera: Chrysomelidae)

“…Eleven PCGs started with ATN, except that nad1 initiated with TTG. Only four PCGs used the typical stop codon 'TAA' and 'TAG', while nine PCGs terminated with incomplete stop codons (TA or T), which was commonly reported in other invertebrates (Masta and Boore 2004). All of the 22 tRNAs have a typical clover-leaf secondary structure, except for trnS1 (tRNA Ser (TCT)) lacking a stable dihydrouridine (DHU) stem, which has been observed in several insects' mtDNA (Kim et al 2012;Song et al 2017).…”

The complete mitochondrial genome of the subterranean crustaceanMetacrangonyx longipes(Amphipoda): A unique gene order and extremely short control region

“…4). Many cases of mismatches in stems have been described in mitochondrial tRNAs, and are supposed to be modified by RNA editing (Ojala et al 1981;Yokobori and Paabo 1995;Masta and Boore 2004;Kilpert and Podsiadlowski 2006). The tRNA genes are present in both strands although most of them (13) are located in the + strand (Table II, Fig.…”