Why barcode? High-throughput multiplex sequencing of mitochondrial genomes for molecular systematics

Area of Science:

• Genomics
• Evolutionary Biology
• Bioinformatics

Background:

• Mitochondrial genome sequencing is crucial for phylogenetics but is often limited by high costs and effort.
• Current taxon sampling for mitochondrial genomes is sporadic, hindering comprehensive evolutionary studies.
• Existing species 'barcodes' primarily rely on the cox1 gene, which may not capture full phylogenetic diversity.

Purpose of the Study:

• To present a simple, cost-effective method for sequencing the complete set of protein-coding mitochondrial genes from pooled samples.
• To demonstrate the utility of this method for phylogenetic analysis and species identification.
• To improve phylogenetic estimates for basal relationships within Coleoptera (beetles).

Main Methods:

• Utilizing the 454/Roche sequencing platform for pooled DNA samples.
• Employing multiplexing without expensive indexing tags ('barcodes').
• Using long-range polymerase chain reaction (PCR) fragments and specific 'bait' sequences for species identification and assembly validation.

Main Results:

• Successfully sequenced 21 nearly complete and 7 partial sets of protein-coding mitochondrial genes from pooled Coleoptera samples.
• Achieved high sequencing depths (∼10–100×) for assembled long contigs.
• Generated an improved estimate of basal relationships in Coleoptera by combining new and existing sequence data.

Conclusions:

• The developed method is a simple, cost-effective, and routine approach for mitochondrial genome sequencing at the species level.
• This technique can generate improved species 'barcodes' beyond the cox1 gene.
• The method facilitates broader taxon sampling for robust phylogenetic analyses.