RESUMO
The phylum Cnidaria is comprised of remarkably diverse and ecologically significant taxa, such as the reef-forming corals, and occupies a basal position in metazoan evolution. The origin of this phylum and the most recent common ancestors (MRCAs) of its modern classes remain mostly unknown, although scattered fossil evidence provides some insights on this topic. Here, we investigate the molecular divergence times of the major taxonomic groups of Cnidaria (27 Hexacorallia, 16 Octocorallia, and 5 Medusozoa) on the basis of mitochondrial DNA sequences of 13 protein-coding genes. For this analysis, the complete mitochondrial genomes of seven octocoral and two scyphozoan species were newly sequenced and combined with all available mitogenomic data from GenBank. Five reliable fossil dates were used to calibrate the Bayesian estimates of divergence times. The molecular evidence suggests that cnidarians originated 741 million years ago (Ma) (95% credible region of 686-819), and the major taxa diversified prior to the Cambrian (543 Ma). The Octocorallia and Scleractinia may have originated from radiations of survivors of the Permian-Triassic mass extinction, which matches their fossil record well.
Assuntos
Antozoários/genética , Evolução Molecular , Genes Mitocondriais , Especiação Genética , Cifozoários/genética , Animais , Antozoários/classificação , Teorema de Bayes , Calibragem , Extinção Biológica , Fósseis , Variação Genética , Genoma Mitocondrial , Funções Verossimilhança , Modelos Genéticos , Filogenia , RNA de Transferência/genética , Cifozoários/classificaçãoRESUMO
Mitochondrial genomes of many nonbilaterian animals show high diversity of genome size and gene content, revealing many intergenic regions (IGRs), diverse repeats and additional genes. Here we present a new complete mitogenome of the cnidarian sea fan species, Calicogorgia granulosa (Anthozoa: Octocorallia) and its novel genomic features. The 20,246 bp of the complete mitogenome, which is the largest among the nine octocorals sequenced to date, contains 13 protein coding genes, 2 rRNAs and a tRNA within its circular form of mitochondrial DNA. We found an identical segmental duplication (S1 and S2, 913 bp) composed of an ORF (672 bp) coding for a hypothetical protein within which Direct Variant Repeat (DVR) expansions reside in-frame to the coding sequence. Additionally, the duplicated segmental DNA showed no variation in nucleotide sequences both between S1 and S2 and across multiple individual samples. Upon these observations, we discuss plausible causes for the intramitochondrial segmental duplication and the absence of sequence variation, and a need for further investigation of the novel ORF as well. In conclusion the present mitogenome of C. granulosa adds more information to our understanding of the diversity and evolution of mitogenomes of nonbilaterian animals.
Assuntos
Antozoários/genética , Genoma Mitocondrial , Sequência de Aminoácidos , Animais , Sequência de Bases , Expansão das Repetições de DNA , DNA Intergênico/genética , DNA Mitocondrial/genética , Dados de Sequência Molecular , Fases de Leitura Aberta , Sequências Repetitivas de Ácido Nucleico , Duplicações Segmentares GenômicasRESUMO
A known monoalkyl glycerol ether, (+/-)-1-nonadecyloxy-2,3-propanediol (1) was isolated from the ethyl acetate extract of a soft coral Dendronephthya gigantea as a weakly cytotoxic constituent against four human cancer cell lines, A549, HT-29, HT-1080, and SNU-638. In addition, a known ceramide, (2S,3R,4E,8E)-N-hexadecanoyl-2-amino-4,8-octadecadiene-1,3-diol (2), was also isolated as an inactive constituent. This is the first report on the isolation of the compounds 1 and 2 from the octocoral, Dendronephthya species.
Assuntos
Alcadienos/isolamento & purificação , Antozoários/química , Antineoplásicos/isolamento & purificação , Ceramidas/isolamento & purificação , Éteres de Glicerila/isolamento & purificação , Alcadienos/química , Animais , Antineoplásicos/química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Ceramidas/química , Ensaios de Seleção de Medicamentos Antitumorais , Éteres de Glicerila/química , Éteres de Glicerila/farmacologia , HumanosRESUMO
Changes in genetic variability and allele frequency can be responses from natural populations when encountering a novel contaminated environment. The genetic diversity and population structuring of natural populations of the gastropod Littorina brevicula from heavy-metal polluted and unpolluted environments along the southeast coast of Korea were examined using two mtDNA markers, cyt b and ND6. This study applied a nested clade analysis to test the existence of structuring association of haplotype distribution with environments (polluted and unpolluted). No genetic differences within cyt b mtDNA were detected between environments. On the other hand, differences in population haplotype diversity and structuring were found within ND6 mtDNA between polluted and unpolluted environments. The ND6-mtDNA haplotype (=genetic) diversity was significant lower in polluted environments. This decreased genetic diversity along with differences in the haplotype distribution within heavy-metal polluted environments compared to those unpolluted ones stand out as emergent effects from pollution at a population level. In this study, we propose the use of different approaches, such as the NCA, that takes into account the rare haplotypes, when assessing the effects of pollution on population genetic structuring.