Complete mitochondrial genome of the brown alga Sargassum horneri (Sargassaceae, Phaeophyceae): genome organization and phylogenetic analyses

The genetics and molecular biology of the ecologically important brown alga, Sargassum horneri (Turner) C. Agardh, are poorly known. In this investigation, the complete nucleotide sequence of the mitochondrial (mt) genome of S. horneri was determined using long PCR and primer walking techniques. The mt genome is 34,606 bp in length and contains 3 ribosomal RNA genes, 25 transfer RNA genes, 35 protein-coding genes, and 2 open reading frames (ORFs). The overall AT content of the genome is 63.84 %, and the intergenic spacers constitute only 4.29 %. The genome organization of S. horneri mitochondrial DNA (mtDNA) is very similar to Fucus vesiculosus except that the counterparts of one putative tRNA(Tyr) gene and ORF379 in Fucus were missing from S. horneri mtDNA. Phylogenetic analyses based on 3 ribosomal RNA genes and 35 protein-coding genes suggest that S. horneri has a closer relationship with F. vesiculosus than other analyzed brown algae. Sargassum horneri is the first species of Sargassaceae to have its mitochondrial genome sequenced. This will provide useful information on both population genetics and molecular evolution of the related species.