2000년도 이후로 많은 분자 연구 논문들이 육각강에서 진행되었으며, 그 결과 방대한 양의 미토콘드리아 유전자 염기서열이 생산되었다. 본 연구에서는 2000년도부터 2009년까지 육각강에 보고된 COI 염기서열과 이들을 활용한 분자 연구 논문들을 분석하기 위하여, 58,323개의 COI 염기서열들을 바탕으로 보고된 488개의 분자 연구 논문들을 26개 목들과 사용된 COI 염기서열들의 5', 3', 중간 위치에 따라 재분류하였다. 세 지역의 COI 염기서열을 이용한 연구 논문의 수는 26개 목들에 따라 매우 다양하였다. 하지만, 7개 목들은 특정 지역의 COI 염기서열들이 선호되었음을 나타내었다. 예를 들어, 파리목과 메뚜기목에서는 5' 지역의 COI 염기서열을 사용하는 논문의 수가 가장 높았으며, 이에 반해 딱정벌레, 이목, 잠자리목, 더듬이벌레목, 대벌레목에서는 3' 지역의 COI 염기서열을 사용하는 논문의 수가 가장 높았다. 2000년 이전에 보고된 84개의 분자 연구 논문들과의 비교를 통해, 2000년부터 2009년까지 딱정벌레목, 파리목, 이목, 대벌레목에서는 1999년 이전에 각 목들에서 주로 사용되었던 COI 염기서열의 특정 지역과 같은 지역을 사용하는 경향성을 보여주었다. 본 연구는 육각강에서 2000년에서 2009년까지 보고되었던 분자 연구 논문 뿐만 아니라 이들 논문에서 사용된 COI 염기서열에 대한 전체적인 경향을 이해하는데 유용한 정보를 제공한다.

DNA barcoding uses a 650 bp segment of the mitochondrial cytochrome c oxidase I (COI) gene as the basis for an identification system for members of the animal kingdom and some other groups of eukaryotes. PCR amplification of the barcode region is a key step in the analytical chain, but it sometimes fails because of a lack of homology between the standard primer sets and target DNA. Two forward PCR primers were developed following analysis of all known arthropod mitochondrial genome arrangements and sequence alignment of the tRNA-W gene which was usually located within 200 bp upstream of the COI gene. These two primers were combined with a standard reverse primer (LepR1) to produce a cocktail which generated a barcode amplicon from 125 of 141 species that included representatives of 121 different families of Hexapoda. High quality sequences were recovered from 79% of the species including groups, such as scale insects, that invariably fail to amplify with standard primers. The current results show that primers designed to bind to highly conserved gene regions upstream of COI will aid the amplification of this gene region in species where standard primers fail and provide valuable information to design a primer for problem groups.

DNA barcode projects in Hexapoda have been initialized and progressed accumulating large number of mitochondrial gene sequences. However, due to large number of data, overview of DNA barcode projects was not conducted until now. Here we reported the current status of DNA barcode projects with the aid of Insect Mitochondrial Genome Database (IMGD; http://www.imgd.org/) which archives 128,562 partial mitochondrial gene sequences (PMEs) of Hexapoda. Among 37 mitochondrial genes, COI has been used popularly (22,379 PMEs;17.40 %) through all 33 orders. Through 513 researches, different parts of COI PME have been utilized differently along with hexapod orders. Inaddition, by calculating genetic divergences of COI PMEs, intra-species and inter-species in 21 hexapod orders were distinguished by 5% divergence and some of mitochondrial genes in certain order present higher genetic divergences than that of COI. Based on these results, we confirmed that DNA barcode is a use ful tool to identify hexapod species and several mitochondrial genes can be good molecular markers to support COI.

The IMGD (Insect Mitochondrial Genome Database; http://www.imgd.org) archives 113,985 partially sequenced hexapod mitochondrial genome entries (PMEs), providing various information such as the number of mitochondrial genes or taxonomic information. The 113,985 PMEs show most PCGs including much larger number of PMEs than rRNAs and tRNAs, and the family, genus, and species information are focused on five orders, Coleoptera, Diptera, Lepidoptera, Hymenoptera, and Hemiptera in 31 hexapoda orders. The alignment of 58,238 COI gene entries shows discordance in fragment length and portion, resulting DNA barcode using 5′-region cannot be applied for all COI gene entries overall hexapod orders.