Undaria mitochondrial large subunit ribosomal DNA (Phaeophyceae, Alariaceae): Structural properties and use for phylogenetic analysis

We sequenced mitochondrial 23S ribosomal DNA (rDNA) from two Undaria species and compared them with homologous sequences from related brown algae. The 23S rDNA sequences from Undaria pinnatifida (Harvey) Suringar were 2707 bp in length, of which 1290–1292 sites were assigned to stem regions and the rest to loop regions in the rRNA secondary structure model. In Undaria undarioides (Yendo) Okamura, the sequences were 2708–2709 bp in length and 1290 sites were assigned to stems. There were three sequence types among the seven U. pinnatifida individuals examined and two among the four U. undarioides individuals. A maximum parsimony analysis of these sequence data with those from related brown algal species resolved a robust monphyly of each of the two Undaria species, suggesting the utilities of 23S rDNA for phylogeny at species or intraspecific level in brown algae. Accounting for variations among sequences parsimoniously, sequence changes were sorted into 423 events, of which 165 were mapped to stems of the secondary structure.