Numerous transposed sequences of mitochondrial cytochrome oxidase I-II in aphids of the genus Sitobion (Hemiptera: Aphididae)

Abstract

Polymerase chain reaction (PCR) products corresponding to 803 bp of the cytochrome oxidase subunits I and II region of mitochondrial DNA (mtDNA COI-II) were deduced to consist of multiple haplotypes in three Sitobion species. We investigated the molecular basis of these observations. PCR products were cloned, and six clones from one individual per species were sequenced. In each individual, one sequence was found commonly, but also two or three divergent sequences were seen. The divergent sequences were shown to be nonmitochondrial by sequencing from purified mtDNA and Southern blotting experiments. All seven nonmitochondrial clones sequenced to completion were unique. Nonmitochondrial sequences have a high proportion of unique sites, and very few characters are shared between nonmitochondrial clones to the exclusion of mtDNA. From these data, we infer that fragments of mtDNA have been transposed separately (probably into aphid chromosomes), at a frequency only known to be equalled in humans. The transposition phenomenon appears to occur infrequently or not at all in closely related genera and other aphids investigated. Patterns of nucleotide substitution in mtDNA inferred over a parsimony tree are very different from those in transposed sequences. Compared with mtDNA, nonmitochondrial sequences have less codon position bias, more even exchanges between A, G, C and T, and a higher proportion of nonsynonymous replacements. Although these data are consistent with the transposed sequences being under less constraint than mtDNA, changes in the nonmitochondrial sequences are not random: there remains significant position bias, and probable excesses of synonymous replacements and of conservative inferred amino acid replacements. We conclude that a proportion of the inferred change in the nonmitochondrial sequences occurred before transposition. We believe that Sitobion aphids (and other species exhibiting mtDNA transposition) may be important for studying the molecular evolution of mtDNA and pseudogenes. However, our data highlight the need to establish the true evolutionary relationships between sequences in comparative investigations.

Efeito da temperatura e umidade relativa do ar no desenvolvimento de Liriomyza sativae Blanchard (Diptera: Agromyzidae) em Vigna unguiculata

“…O método empregado na caracterização molecular foi baseado em Scheffer & Lewis (2005). Três adultos de Liriomyza foram obtidos da criação estoque e utilizados para a extração individual do DNA genômico pelo método de sal (Sunnucks & Hales 1996). A caracterização foi baseada no sequenciamento da porção do gene da citocromo oxidase I (COI), após amplifi cação em termociclador (Techne Endurance TC-512, Ramsey,MT) programado a 92°C por 5 min (1x), seguido de 35 ciclos a 92°C por 1 min, 53°C por 1 mim e 72°C por 1 min30s, e extensão fi nal por 5 min a 72°C.…”

Biogeography and speciation of a direct developing frog from the coastal arid zone of Western Australia

“…Sequences were translated using the mammalian mitochondrial genetic code option in Sequencher 3.0, and an open reading frame was observed in all sequences. Thus sequences were assumed to be genuine mitochondrial copies and not nuclear paralogues (Sunnucks and Hales, 1996). Haplotype sequences have been deposited in GenBank (Accession Nos.…”

Pronounced genetic differentiation of small, isolated and fragmented tilapia populations inhabiting the Magadi Soda Lake in Kenya

“…4a). Several scenarios may lead to such a pattern; incomplete lineage sorting resulting in shared polymorphisms, several repeated colonisation events, existence of hybridization and subsequent introgressive gene flow among groups or inadequate taxonomic data which underestimates the extant species diversity within a set of individuals (Sunnucks & Hales, 1996;Maddison & Knowles, 2006). Magadi tilapia is considered a relic of a fish that inhabited paleo-lake Orolonga which split to form the present-day Lake Magadi and Lake Natron over 13,000 years ago.…”