Phylogenetic position of the coral symbiont Ostreobium (Ulvophyceae) inferred from chloroplast genome data

Type Article
Date 2017-08
Language English
Author(s) Verbruggen HeroenORCID1, Marcelino Vanessa R.1, Guiry Michael D.2, Cremen Ma. Chiela M.1, Jackson Christopher J.1
Affiliation(s) 1 : Univ Melbourne, Sch Biosci, Melbourne, Vic 3010, Australia.
2 : Natl Univ Ireland, Ryan Inst, AlgaeBase, Galway H91 TK33, Ireland.
Source Journal Of Phycology (0022-3646) (Wiley), 2017-08 , Vol. 53 , N. 4 , P. 790-803
DOI 10.1111/jpy.12540
WOS© Times Cited 23
Keyword(s) Bryopsidales, chloroplast genome, coral symbiosis, Dasycladales, molecular phylogenetics, Ostreobium, phylogenomics

The green algal genus Ostreobium is an important symbiont of corals, playing roles in reef decalcification and providing photosynthates to the coral during bleaching events. A chloroplast genome of a cultured strain of Ostreobium was available, but low taxon sampling and Ostreobium's early-branching nature left doubt about its phylogenetic position. Here, we generate and describe chloroplast genomes from four Ostreobium strains as well as Avrainvillea mazei and Neomeris sp., strategically sampled earlybranching lineages in the Bryopsidales and Dasycladales respectively. At 80,584 bp, the chloroplast genome of Ostreobium sp. HV05042 is the most compact yet found in the Ulvophyceae. The Avrainvillea chloroplast genome is similar to 94 kbp and contains introns in infA and cysT that have nearly complete sequence identity except for an open reading frame (ORF) in infA that is not present in cysT. In line with other bryopsidalean species, it also contains regions with possibly bacteria-derived ORFs. The Neomeris data did not assemble into a canonical circular chloroplast genome but a large number of contigs containing fragments of chloroplast genes and showing evidence of long introns and intergenic regions, and the Neomeris chloroplast genome size was estimated to exceed 1.87 Mb. Chloroplast phylogenomics and 18S nrDNA data showed strong support for the Ostreobium lineage being sister to the remaining Bryopsidales. There were differences in branch support when outgroups were varied, but the overall support for the placement of Ostreobium was strong. These results permitted us to validate two suborders and introduce a third, the Ostreobineae.

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Publisher's official version 14 1 MB Open access
Figure S1. Conserved blocks between Avrainvillea and members of the Bryopsidineae, Halimedineae and Ostreobineae suborders. 3 73 KB Open access
Figure S2. Maximum likelihood trees with bootstrap values for all analysis conditions. The title of each page corresponds to analysis conditions in Table 2. 30 878 KB Open access
Appendix S1. Alignments used to infer all maximum likelihood trees, in Phylip format. 1253 2 MB Open access
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Verbruggen Heroen, Marcelino Vanessa R., Guiry Michael D., Cremen Ma. Chiela M., Jackson Christopher J. (2017). Phylogenetic position of the coral symbiont Ostreobium (Ulvophyceae) inferred from chloroplast genome data. Journal Of Phycology, 53(4), 790-803. Publisher's official version : , Open Access version :