Undaria pinnatifida is one of the most important economic marine algae and key components of coastal ecosystems. Undaria pinnatifida owns a typical heteromorphic, diplohaplontic life cycle. We present the complete sequence of mitochondrial genome of U. pinnatifida, focusing on genome organization and phylogenetic relationship between different brown algae lineages. The size of U. pinnatifida mitochondrial DNA is 37,402 bp, including 3 rRNAs, 25 tRNAs, 35 proteins, as well as 3 ORFs. No intron is found and most genes are encoded on the H-strand. The phylogenetic trees (BI) constructed on 35 protein-coding genes from 17 species proved that Saccharina has a closer relationship with Laminaria than that with Undaria. The results supported the conclusion that Alariaceae is sister genus to the Laminariaceae. Above researches will facilitate the understanding of evolutionary relationship within brown algae.
Keywords: Laminariales; Undaria pinnatifida; mitochondrial genome.