Larval settlement rates, genetic structure, and gene flow of broadcast-spawning (Acropora tenuis) and planula-brooding (Stylophora pistillata) corals (Scleractinia) were compared within a 500 km range in the Ryukyu Archipelago. We conducted a laboratory experiment to investigate planula settlement rates, and a broad sampling survey to determine genetic variation in both species in the Archipelago. In the laboratory experiment, the planulae of S. pistillata settled a few hours after release, while those of A. tenuis started to settle at least 4 d after the release of gametes. The survival rates and competency periods of larvae were higher and longer for A. tenuis than for S. pistillata. These results suggest that broader dispersal is more likely for A. tenuis than for S. pistillata. In the population genetic analysis, we measured local (2 stations in a region) and regional (Okinawa, Kerama and Yaeyama) patterns of genetic variation with allozyme electrophoresis. We also inferred the levels of gene flow in the 2 species. In the study area, gene flow (N e m) and genetic distance (D) were, respectively, higher and smaller for the spawner A. tenuis (N e m = 3.5 to 16.4, D = 0.028 to 0.187) than for the brooder S. pistillata (N e m = 0.9 to 1.5, D = 0.026 to 0.309). Therefore, the planulae settlement rates were well in agreement with gene flow. In addition, for both species, N e m between the Okinawa and Kerama regions (30 to 150 km apart; N e m = 9.4 to 22.5 in A. tenuis and 1.4 to 3.3 in S. pistillata) was higher than that between the Okinawa-Kerama and Yaeyama regions (up to 500 km apart; N e m = 3.1 to 9.4 in A. tenuis and 0.5 to 1.4 in S. pistillata). The results suggest that coral populations in the Kerama Island are a major source of the coral planulae needed for the recovery of both brooding and spawning coral communities around the Okinawa Islands, after the mass-bleaching event in 1998. KEY WORDS: Scleractinian coral · Reproductive mode · Competency · Gene flow · Larvae source · Ryukyu ArchipelagoResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 256: 87-97, 2003 1985, , Harrison & Wallace 1990. This suggests that the dispersal potential of brooded planula is more restricted than that of planulae originating from spawning, because of the shorter pre-competency period in brooders versus spawners. Nevertheless, a previous comprehensive study of the population genetics of scleractinian corals does not fully support this hypothesis. Ayre & Hughes (2000) studied the population genetics of 5 brooding and 4 spawning coral species on the Great Barrier Reef (GBR) of Australia. They estimated that, in 3 of the 5 brooding species and all of the spawning species, larval dispersal was sufficient to maintain moderate to high levels of gene flow along the entire GBR. In contrast, they estimated that local populations of the remaining 2 brooding species (Stylophora pistillata and Seriatopora hystrix) were genetically more weakly connected than the other 7 species.I...
Nocardiosis caused by Nocardia seriolae is one of the major threats in the aquaculture of Seriola species (yellowtail; S. quinqueradiata, amberjack; S. dumerili and kingfish; S. lalandi) in Japan. Here, we report the complete nucleotide genome sequence of N. seriolae UTF1, isolated from a cultured yellowtail. The genome is a circular chromosome of 8,121,733 bp with a G+C content of 68.1% that encodes 7,697 predicted proteins. In the N. seriolae UTF1 predicted genes, we found orthologs of virulence factors of pathogenic mycobacteria and human clinical Nocardia isolates involved in host cell invasion, modulation of phagocyte function and survival inside the macrophages. The virulence factor candidates provide an essential basis for understanding their pathogenic mechanisms at the molecular level by the fish nocardiosis research community in future studies. We also found many potential antibiotic resistance genes on the N. seriolae UTF1 chromosome. Comparative analysis with the four existing complete genomes, N. farcinica IFM 10152, N. brasiliensis HUJEG-1 and N. cyriacigeorgica GUH-2 and N. nova SH22a, revealed that 2,745 orthologous genes were present in all five Nocardia genomes (core genes) and 1,982 genes were unique to N. seriolae UTF1. In particular, the N. seriolae UTF1 genome contains a greater number of mobile elements and genes of unknown function that comprise the differences in structure and gene content from the other Nocardia genomes. In addition, a lot of the N. seriolae UTF1-specific genes were assigned to the ABC transport system. Because of limited resources in ocean environments, these N. seriolae UTF1 specific ABC transporters might facilitate adaptation strategies essential for marine environment survival. Thus, the availability of the complete N. seriolae UTF1 genome sequence will provide a valuable resource for comparative genomic studies of N. seriolae isolates, as well as provide new insights into the ecological and functional diversity of the genus Nocardia.
BackgroundThe order Tetraodontiformes consists of approximately 429 species of fishes in nine families. Members of the order exhibit striking morphological diversity and radiated into various habitats such as freshwater, brackish and coastal waters, open seas, and deep waters along continental shelves and slopes. Despite extensive studies based on both morphology and molecules, there has been no clear resolution except for monophyly of each family and sister-group relationships of Diodontidae + Tetraodontidae and Balistidae + Monacanthidae. To address phylogenetic questions of tetraodontiform fishes, we used whole mitochondrial genome (mitogenome) sequences from 27 selected species (data for 11 species were newly determined during this study) that fully represent all families and subfamilies of Tetraodontiformes (except for Hollardinae of the Triacanthodidae). Partitioned maximum likelihood (ML) and Bayesian analyses were performed on two data sets comprising concatenated nucleotide sequences from 13 protein-coding genes (all positions included; third codon positions converted into purine [R] and pyrimidine [Y]), 22 transfer RNA and two ribosomal RNA genes (total positions = 15,084).ResultsThe resultant tree topologies from the two data sets were congruent, with many internal branches showing high support values. The mitogenomic data strongly supported monophyly of all families and subfamilies (except the Tetraodontinae) and sister-group relationships of Balistidae + Monacanthidae and Tetraodontidae + Diodontidae, confirming the results of previous studies. However, we also found two unexpected basal splits into Tetraodontoidei (Triacanthidae + Balistidae + Monacanthidae + Tetraodontidae + Diodontidae + Molidae) and Triacanthodoidei (Ostraciidae + Triodontidae + Triacanthodidae).ConclusionThis basal split into the two clades has never been reported and challenges previously proposed hypotheses based on both morphology and nuclear gene sequences. It is likely that the basal split had involved ecological diversification, because most members of Tetraodontoidei exclusively occur in shallow waters (freshwater, brackish and coastal waters, and open seas), while those of Triacanthodoidei occur mainly in relatively deep waters along continental shelves and slopes except for more derived ostraciids. This suggests that the basal split between the two clades led to subsequent radiation into the two different habitats.
We have established a new transgenic mouse mutagenicity assay for the efficient detection of point mutations and deletions in vivo (Nohmi et al. [1996] Env. Mol. Mutagen. 28:465–470). In this assay, the gpt gene of Escherichia coli is used as a reporter for the detection of point mutations. Treatment of mice with ethylnitrosourea (ENU, 150 mg/kg) enhances by several‐fold the mutant frequency of gpt in bone marrow. Here, we report the mutation spectra of the gpt gene recovered from bone marrow of ENU‐treated and untreated transgenic mice. In the gpt mutants rescued from ENU‐treated mice, more than 90% of the mutations were base change mutations; the predominant types were A:T to T:A transversions and G:C to A:T transitions. On the contrary, in the mutants rescued from untreated mice, 54% were base substitutions and the remainders were short deletions and insertions. Among untreated mice, the most frequently observed base substitution was G:C to A:T transitions (7/14 mutants). Three of these occurred at 5′‐CpG‐3′ sites. Interestingly, the mutation spectra of the gpt gene were different from those of the gpt gene in ENU‐treated and untreated E.coli, whereas they were similar to those of the lacZ and lacI genes in ENU‐treated and untreated other transgenic mice or cultured mammalian cells. We also report the establishment of homozygous transgenic mice that have transgene λEG10 DNA in both chromosome 17 of C57BL/6J mouse. Environ. Mol. Mutagen. 34:1–8, 1999 © 1999 Wiley‐Liss, Inc.
Despite the importance of genome rearrangement in the etiology of cancer and human genetic disease, deletion mutations are poorly detectable by transgenic rodent mutagenicity tests. To facilitate the detection and molecular analysis of deletion mutations in vivo, we established a transgenic mouse model harboring a λEG10 shuttle vector that includes the red and gam genes for Spi− (sensitive to P2 interference) selection [Nohmi et al. (1996] Environ. Mol. Mutagen. 28:465–470]. This selection has a great advantage over other genetic systems, because phage deletion mutants can be preferentially selected as Spi− plaques, which can then be subjected to molecular analysis. Here, we show nucleotide sequences of 41 junctions of deletion mutations induced by γ‐irradiation. Unlike spontaneous deletion mutants, more than half of the large deletions occurred between short homologous sequences from one to eight bp. The remaining junctions had no such homologous sequences. Intriguingly, two Spi− mutants had P (palindrome)‐like nucleotide additions at the breakpoints, which are frequently observed in the coding junctions of V(D)J recombination, suggesting that broken DNA molecules with hairpin structures can be intermediates in the repair of radiation‐induced double‐strand breaks. We conclude that Spi− selection is useful for the efficient detection of deletion mutations in vivo and that most rearrangements induced by γ‐rays in mice are mediated by illegitimate recombination through DNA end‐joining. Environ. Mol. Mutagen. 34:9–15, 1999 © 1999 Wiley‐Liss, Inc.
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