The mitochondrial genome of the brown alga Laminaria digitata: a comparative analysis

• Published in: European journal of phycology 2002-05, Vol.37 (2), p.163-172, Article S0967026202003542
• Main Authors: OUDOT-LE SECQ, MARIE-PIERRE, KLOAREG, BERNARD, LOISEAUX-DE GOËR, SUSAN
• Format: Article
• Language: English
• Subjects: brown algae; cox2 gene; evolution of mitochondria; heterokonts; Laminaria digitata; Marine; mitochondrial DNA; nad11 gene; Phaeophyta; Pylaiella littoralis; rn5 gene
• ISSN: 0967-0262; 1469-4433
• DOI: 10.1017/S0967026202003542

We report here the complete sequence of the mitochondrial genome of the brown alga Laminaria digitata (Hudson) J.V. Lamouroux. L. digitata mtDNA is a circular molecule of 38,007 bp (64·9% A+T), encoding 63 genes and 3 ORFs and with only 6·7% of non-coding sequences. Based on gene content and order, its overall organization is very similar to that of the mitochondrial genome of Pylaiella littoralis, another brown alga belonging to a different sublineage of the Phaeophyceae. In particular, the two genomes share unusual features, which hence could be unique to brown algae among the heterokont lineage, namely the presence of a rn5 gene, a short nad11 gene, a cox2 gene with a large in-frame insertion and α-proteobacterial-like promoter sequences. On the other hand, L. digitata lacks the sequences which are thought to have been transmitted horizontally to the P. littoralis genome, that is, the group-II introns in the rnl and cox1 genes, and it features only traces of an ancestral T7-like RNA polymerase. Distance phylogenetic trees inferred from concatenated mitochondrial genes confirm that speciation of brown algae occurred recently compared to other heterokonts.