Multiple origins of the ascidian-Prochloron symbiosis: molecular phylogeny of photosymbiotic and non-symbiotic colonial ascidians inferred from 18S rDNA sequences.
In the tropics, certain didemnid ascidians harbor the prokaryotic photosymbiont Prochloron. To date, this photosymbiosis has been found in four didemnid genera that include non-symbiotic species. Here, we report the molecular phylogeny of symbiotic and non-symbiotic didemnids based on their 18S rDNA sequences. The data cover all four genera containing symbiotic species and one other genus comprised of only non-symbiotic species. Near-complete nucleotide sequences of 18S rDNAs were determined for four non-didemnid species and 52 didemnid samples (five genera), including 48 photosymbiotic samples collected from the Ryukyu Archipelago, the Great Barrier Reef, Hawaii, and Bali. Our phylogenetic trees indicated a monophyletic origin of the family Didemnidae, as well as each of the didemnid genera. The results strongly support the hypothesis that establishment of the ascidian-Prochloron symbiosis occurred independently in the Didemnidae lineage at least once in each of the genera that possess symbiotic species.
Laboratory for Cellular Biochemistry, Department of Molecular Biology, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo 192-0392, Japan.
Shin-Ichi
S
Yokobori
Atsushi
A
Kurabayashi
Brett A
BA
Neilan
Tadashi
T
Maruyama
Euichi
E
Hirose
D000818:Animals; D001483:Base Sequence; D006801:Humans; D008969:Molecular Sequence Data; D018462:Photobiology; D010802:Phylogeny; D019691:Prochloron / Q000502:physiology*; D012337:RNA, Ribosomal, 18S / Q000235:genetics*; D017385:Sequence Homology; D012689:Sequence Homology, Nucleic Acid; D013559:Symbiosis / Q000235:genetics*; D014561:Urochordata / Q000235:genetics* / Q000502:physiology*
D012337:RNA, Ribosomal, 18S