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Molecular phylogeny of two unusual brown algae, Phaeostrophion irregulare and Platysiphon glacialis, proposal of the Stschapoviales ord. nov. and Platysiphonaceae fam. nov., and a re-examination of divergence times for brown algal orders.

ABSTRACT: The molecular phylogeny of brown algae was examined using concatenated DNA sequences of seven chloroplast and mitochondrial genes (atpB, psaA, psaB, psbA, psbC, rbcL, and cox1). The study was carried out mostly from unialgal cultures; we included Phaeostrophion irregulare and Platysiphon glacialis because their ordinal taxonomic positions were unclear. Overall, the molecular phylogeny agreed with previously published studies, however, Platysiphon clustered with Halosiphon and Stschapovia and was paraphyletic with the Tilopteridales. Platysiphon resembled Stschapovia in showing remarkable morphological changes between young and mature thalli. Platysiphon, Halosiphon and Stschapovia also shared parenchymatous, terete, erect thalli with assimilatory filaments in whorls or on the distal end. Based on these results, we proposed a new order Stschapoviales and a new family Platysiphonaceae. We proposed to include Phaeostrophion in the Sphacelariales, and we emended the order to include this foliose member. Finally, using basal taxa not included in earlier studies, the origin and divergence times for brown algae were re-investigated. Results showed that the Phaeophyceae branched from Schizocladiophyceae ~260 Ma during the Permian Period. The early diverging brown algae had isomorphic life histories, whereas the derived taxa with heteromorphic life histories evolved 155-110 Ma when they branched from the basal taxa. Based on these results, we propose that the development of heteromorphic life histories and their success in the temperate and cold-water regions was induced by the development of the remarkable seasonality caused by the breakup of Pangaea. Most brown algal orders had diverged by roughly 60 Ma, around the last mass extinction event during the Cretaceous Period, and therefore a drastic climate change might have triggered the divergence of brown algae.

SUBMITTER: Kawai H

PROVIDER: S-EPMC5054896 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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Publications

Molecular phylogeny of two unusual brown algae, Phaeostrophion irregulare and Platysiphon glacialis, proposal of the Stschapoviales ord. nov. and Platysiphonaceae fam. nov., and a re-examination of divergence times for brown algal orders.

Kawai Hiroshi H Hanyuda Takeaki T Draisma Stefano G A SG Wilce Robert T RT Andersen Robert A RA

Journal of phycology 20150927 5

The molecular phylogeny of brown algae was examined using concatenated DNA sequences of seven chloroplast and mitochondrial genes (atpB, psaA, psaB, psbA, psbC, rbcL, and cox1). The study was carried out mostly from unialgal cultures; we included Phaeostrophion irregulare and Platysiphon glacialis because their ordinal taxonomic positions were unclear. Overall, the molecular phylogeny agreed with previously published studies, however, Platysiphon clustered with Halosiphon and Stschapovia and was ...[more]

PMID: 26986888

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Project description:A novel Gram-negative, motile, aerobic rod-shaped bacterium designated BGMRC 2031T was isolated from mangrove sediment collected from Guangxi Province, China. Optimal growth occurred at 28 °C and pH 7.0-8.0 in the presence of 1% (w/v) NaCl. Alignment based on 16S rRNA gene sequences indicated that strain BGMRC 2031T is most closely related to Sodalis praecaptivus HS1T (95.6%, sequence similarity), followed by Biostraticola tofi DSM 19580T (95.5%), Sodalis glossinidius DSM 16929T (95.4%), and Brenneria goodwinii FRB141T (94.9%) sequence similarity. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain BGMRC 2031T formed a distinct branch in a robust cluster and revealed that strain BGMRC 2031T, genera Biostraticola and Sodalis, formed a novel family-level clade in the order Enterobacterales. The novel strain showed an average nucleotide similarity of 74.7%, 74.2%, and 73.1% for S. praecaptivus HS1T, S. glossinidius DSM 16929T, and B. tofi DSM 19580T, respectively. The genomes of the BGMRC 2031T shared the presence of a riboflavin synthesis gene cluster. The menaquinones of strain BGMRC 2031T were MK-8 and Q-8, which were similar to those of genus Biostraticola. The major fatty acids (> 10%) were C16:0 (19.9%), summed feature 2 (iso-C16:1 and/or C14:0 3-OH, 18.10%), summed feature 3 (C16:1 ω7c and/or C16:1 ω6c, 15.3%), C12:0 (13.9%), C17:0 cyclo (11.4%), and C14:0 (10.4%). The main polar lipids were phosphatidyl methylethanolamine, phosphatidyl glycerol, diphosphatidyl glycerol, phosphatidyl inositol, one unidentified phospholipid, and one unknown polar lipid. The G+C content of strain BGMRC 2031T was 55.4%. Strain BGMRC 2031T could extend the mean lifespan and maximum lifespan of Caenorhabditis elegans by 4.5% and 12.5%, respectively. Overall, the results of this study indicate that BGMRC 2031T is a novel species in a new genus, for which the name Bruguierivorax albus gen. nov. sp. nov. is proposed, and the type of strain is designated as BGMRC 2031T (= NBRC 111907T = KCTC 52119T). In addition, a novel family, Bruguierivoracaceae fam. nov., is proposed to accommodate the genera Bruguierivorax, Biostraticola, and Sodalis.

Dataset Information

Molecular phylogeny of two unusual brown algae, Phaeostrophion irregulare and Platysiphon glacialis, proposal of the Stschapoviales ord. nov. and Platysiphonaceae fam. nov., and a re-examination of divergence times for brown algal orders.

Publications

Molecular phylogeny of two unusual brown algae, Phaeostrophion irregulare and Platysiphon glacialis, proposal of the Stschapoviales ord. nov. and Platysiphonaceae fam. nov., and a re-examination of divergence times for brown algal orders.

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