Phylogenetic position of the coral symbiont Ostreobium (Ulvophyceae) inferred from chloroplast genome data. Issue 4 (12th May 2017)

• Record Type: Journal Article
• Authors: Verbruggen, Heroen; Marcelino, Vanessa R.; Guiry, Michael D.; Cremen, Ma. Chiela M.; Jackson, Christopher J.
• Editors: Graham, L.
• Is Part Of: Journal of phycology. Volume 53:Issue 4(2017:Aug.)
• Page Start: 790
• Page End: 803
• Publication Date: 2017-05-12
• Subjects: Bryopsidales -- chloroplast genome -- coral symbiosis -- Dasycladales -- molecular phylogenetics -- Ostreobium -- phylogenomics; Algae -- Periodicals; 579.8
• DOI: 10.1111/jpy.12540
• Languages: English
• ISSNs: 0022-3646

Abstract

Abstract : 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 early‐branching 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 ~94 kbp and contains introns in inf A and cys T that have nearly complete sequence identity except for an open reading frame (ORF) in inf A that is not present in cys T. 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.