Displaying publications 1 - 20 of 62 in total

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  1. Tan MH, Gan HM, Lee YP, Bracken-Grissom H, Chan TY, Miller AD, et al.
    Sci Rep, 2019 Jul 24;9(1):10756.
    PMID: 31341205 DOI: 10.1038/s41598-019-47145-0
    The emergence of cost-effective and rapid sequencing approaches has resulted in an exponential rise in the number of mitogenomes on public databases in recent years, providing greater opportunity for undertaking large-scale comparative genomic and systematic research. Nonetheless, current datasets predominately come from small and disconnected studies on a limited number of related species, introducing sampling biases and impeding research of broad taxonomic relevance. This study contributes 21 crustacean mitogenomes from several under-represented decapod infraorders including Polychelida and Stenopodidea, which are used in combination with 225 mitogenomes available on NCBI to investigate decapod mitogenome diversity and phylogeny. An overview of mitochondrial gene orders (MGOs) reveals a high level of genomic variability within the Decapoda, with a large number of MGOs deviating from the ancestral arthropod ground pattern and unevenly distributed among infraorders. Despite the substantial morphological and ecological variation among decapods, there was limited evidence for correlations between gene rearrangement events and species ecology or lineage specific nucleotide substitution rates. Within a phylogenetic context, predicted scenarios of rearrangements show some MGOs to be informative synapomorphies for some taxonomic groups providing strong independent support for phylogenetic relationships. Additional comparisons for a range of mitogenomic features including nucleotide composition, strand asymmetry, unassigned regions and codon usage indicate several clade-specific trends that are of evolutionary and ecological interest.
  2. Md Zoqratt MZH, Eng WWH, Thai BT, Austin CM, Gan HM
    PeerJ, 2018;6:e5826.
    PMID: 30397546 DOI: 10.7717/peerj.5826
    Aquaculture production of the Pacific white shrimp is the largest in the world for crustacean species. Crucial to the sustainable global production of this important seafood species is a fundamental understanding of the shrimp gut microbiota and its relationship to the microbial ecology of shrimp pond. This is especially true, given the recently recognized role of beneficial microbes in promoting shrimp nutrient intake and in conferring resistance against pathogens. Unfortunately, aquaculture-related microbiome studies are scarce in Southeast Asia countries despite the severe impact of early mortality syndrome outbreaks on shrimp production in the region. In this study, we employed the 16S rRNA amplicon (V3-V4 region) sequencing and amplicon sequence variants (ASV) method to investigate the microbial diversity of shrimp guts and pond water samples collected from aquaculture farms located in Malaysia and Vietnam. Substantial differences in the pond microbiota were observed between countries with the presence and absence of several taxa extending to the family level. Microbial diversity of the shrimp gut was found to be generally lower than that of the pond environments with a few ubiquitous genera representing a majority of the shrimp gut microbial diversity such as Vibrio and Photobacterium, indicating host-specific selection of microbial species. Given the high sequence conservation of the 16S rRNA gene, we assessed its veracity at distinguishing Vibrio species based on nucleotide alignment against type strain reference sequences and demonstrated the utility of ASV approach in uncovering a wider diversity of Vibrio species compared to the conventional OTU clustering approach.
  3. Tan MH, Gan HM, Lee YP, Poore GC, Austin CM
    PeerJ, 2017;5:e2982.
    PMID: 28265498 DOI: 10.7717/peerj.2982
    BACKGROUND: Whole mitochondrial DNA is being increasingly utilized for comparative genomic and phylogenetic studies at deep and shallow evolutionary levels for a range of taxonomic groups. Although mitogenome sequences are deposited at an increasing rate into public databases, their taxonomic representation is unequal across major taxonomic groups. In the case of decapod crustaceans, several infraorders, including Axiidea (ghost shrimps, sponge shrimps, and mud lobsters) and Caridea (true shrimps) are still under-represented, limiting comprehensive phylogenetic studies that utilize mitogenomic information.

    METHODS: Sequence reads from partial genome scans were generated using the Illumina MiSeq platform and mitogenome sequences were assembled from these low coverage reads. In addition to examining phylogenetic relationships within the three infraorders, Axiidea, Gebiidea, and Caridea, we also investigated the diversity and frequency of codon usage bias and mitogenome gene order rearrangements.

    RESULTS: We present new mitogenome sequences for five shrimp species from Australia that includes two ghost shrimps, Callianassa ceramica and Trypaea australiensis, along with three caridean shrimps, Macrobrachium bullatum, Alpheus lobidens, and Caridina cf. nilotica. Strong differences in codon usage were discovered among the three infraorders and significant gene order rearrangements were observed. While the gene order rearrangements are congruent with the inferred phylogenetic relationships and consistent with taxonomic classification, they are unevenly distributed within and among the three infraorders.

    DISCUSSION: Our findings suggest potential for mitogenome rearrangements to be useful phylogenetic markers for decapod crustaceans and at the same time raise important questions concerning the drivers of mitogenome evolution in different decapod crustacean lineages.

  4. Tan MH, Gan HM, Schultz MB, Austin CM
    Mol Phylogenet Evol, 2015 Apr;85:180-8.
    PMID: 25721538 DOI: 10.1016/j.ympev.2015.02.009
    The increased rate at which complete mitogenomes are being sequenced and their increasing use for phylogenetic studies have resulted in a bioinformatic bottleneck in preparing and utilising such data for phylogenetic analysis. Hence, we present MitoPhAST, an automated tool that (1) identifies annotated protein-coding gene features and generates a standardised, concatenated and partitioned amino acid alignment directly from complete/partial GenBank/EMBL-format mitogenome flat files, (2) generates a maximum likelihood phylogenetic tree using optimised protein models and (3) reports various mitochondrial genes and sequence information in a table format. To demonstrate the capacity of MitoPhAST in handling a large dataset, we used 81 publicly available decapod mitogenomes, together with eight new complete mitogenomes of Australian freshwater crayfishes, including the first for the genus Gramastacus, to undertake an updated test of the monophyly of the major groups of the order Decapoda and their phylogenetic relationships. The recovered phylogenetic trees using both Bayesian and ML methods support the results of studies using fragments of mtDNA and nuclear markers and other smaller-scale studies using whole mitogenomes. In comparison to the fragment-based phylogenies, nodal support values are generally higher despite reduced taxon sampling suggesting there is value in utilising more fully mitogenomic data. Additionally, the simple table output from MitoPhAST provides an efficient summary and statistical overview of the mitogenomes under study at the gene level, allowing the identification of missing or duplicated genes and gene rearrangements. The finding of new mtDNA gene rearrangements in several genera of Australian freshwater crayfishes indicates that this group has undergone an unusually high rate of evolutionary change for this organelle compared to other major families of decapod crustaceans. As a result, freshwater crayfishes are likely to be a useful model for studies designed to understand the evolution of mtDNA rearrangements. We anticipate that our bioinformatics pipeline will substantially help mitogenome-based studies increase the speed, accuracy and efficiency of phylogenetic studies utilising mitogenome information. MitoPhAST is available for download at https://github.com/mht85/MitoPhAST.
  5. Tan MH, Gan HM, Lee YP, Linton S, Grandjean F, Bartholomei-Santos ML, et al.
    Mol Phylogenet Evol, 2018 10;127:320-331.
    PMID: 29800651 DOI: 10.1016/j.ympev.2018.05.015
    The infraorder Anomura consists of a morphologically and ecologically heterogeneous group of decapod crustaceans, and has attracted interest from taxonomists for decades attempting to find some order out of the seemingly chaotic diversity within the group. Species-level diversity within the Anomura runs the gamut from the "hairy" spindly-legged yeti crab found in deep-sea hydrothermal vent environments to the largest known terrestrial invertebrate, the robust coconut or robber crab. Owing to a well-developed capacity for parallel evolution, as evidenced by the occurrence of multiple independent carcinization events, Anomura has long tested the patience and skill of both taxonomists attempting to find order, and phylogeneticists trying to establish stable hypotheses of evolutionary inter-relationships. In this study, we performed genome skimming to recover the mitogenome sequences of 12 anomuran species including the world's largest extant invertebrate, the robber crab (Birgus latro), thereby over doubling these resources for this group, together with 8 new brachyuran mitogenomes. Maximum-likelihood (ML) and Bayesian-inferred (BI) phylogenetic reconstructions based on amino acid sequences from mitogenome protein-coding genes provided strong support for the monophyly of the Anomura and Brachyura and their sister relationship, consistent with previous studies. The majority of relationships within families were supported and were largely consistent with current taxonomic classifications, whereas many relationships at higher taxonomic levels were unresolved. Nevertheless, we have strong support for a polyphyletic Paguroidea and recovered a well-supported clade of a subset of paguroids (Diogenidae + Coenobitidae) basal to all other anomurans, though this requires further testing with greater taxonomic sampling. We also introduce a new feature to the MitoPhAST bioinformatics pipeline (https://github.com/mht85/MitoPhAST) that enables the extraction of mitochondrial gene order (MGO) information directly from GenBank files and clusters groups based on common MGOs. Using this tool, we compared MGOs across the Anomura and Brachyura, identifying Anomura as a taxonomic "hot spot" with high variability in MGOs among congeneric species from multiple families while noting the broad association of highly-rearranged MGOs with several anomuran lineages inhabiting extreme niches. We also demonstrate the value of MGOs as a source of novel synapomorphies for independently reinforcing tree-based relationships and for shedding light on relationships among challenging groups such as the Aegloidea and Lomisoidea that were unresolved in phylogenetic reconstructions. Overall, this study contributes a substantial amount of new genetic material for Anomura and attempts to further resolve anomuran evolutionary relationships where possible based on a combination of sequence and MGO information. The new feature in MitoPhAST adds to the relatively limited number of bioinformatics tools available for MGO analyses, which can be utilized widely across animal groups.
  6. Gan HM, Tan MH, Lee YP, Schultz MB, Horwitz P, Burnham Q, et al.
    Mol Phylogenet Evol, 2018 01;118:88-98.
    PMID: 28966124 DOI: 10.1016/j.ympev.2017.09.022
    To further understand the evolutionary history and mitogenomic features of Australia's highly distinctive freshwater crayfish fauna, we utilized a recently described rapid mitogenome sequencing pipeline to generate 24 new crayfish mitogenomes including a diversity of burrowing crayfish species and the first for Astacopsis gouldi, the world's largest freshwater invertebrate. Whole mitogenome-based phylogeny estimates using both Bayesian and Maximum Likelihood methods substantially strengthen existing hypotheses for systematic relationships among Australian freshwater crayfish with evidence of pervasive diversifying selection and accelerated mitochondrial substitution rate among the members of the clade representing strongly burrowing crayfish that may reflect selection pressures for increased energy requirement for adaptation to terrestrial environment and a burrowing lifestyle. Further, gene rearrangements are prevalent in the burrowing crayfish mitogenomes involving both tRNA and protein coding genes. In addition, duplicated control regions were observed in two closely related Engaeus species, together with evidence for concerted evolution. This study significantly adds to the understanding of Australian freshwater crayfish evolutionary relationships and suggests a link between mitogenome evolution and adaptation to terrestrial environments and a burrowing lifestyle in freshwater crayfish.
  7. Harrisson KA, Amish SJ, Pavlova A, Narum SR, Telonis-Scott M, Rourke ML, et al.
    Mol Ecol, 2017 Nov;26(22):6253-6269.
    PMID: 28977721 DOI: 10.1111/mec.14368
    Adaptive differences across species' ranges can have important implications for population persistence and conservation management decisions. Despite advances in genomic technologies, detecting adaptive variation in natural populations remains challenging. Key challenges in gene-environment association studies involve distinguishing the effects of drift from those of selection and identifying subtle signatures of polygenic adaptation. We used paired-end restriction site-associated DNA sequencing data (6,605 biallelic single nucleotide polymorphisms; SNPs) to examine population structure and test for signatures of adaptation across the geographic range of an iconic Australian endemic freshwater fish species, the Murray cod Maccullochella peelii. Two univariate gene-association methods identified 61 genomic regions associated with climate variation. We also tested for subtle signatures of polygenic adaptation using a multivariate method (redundancy analysis; RDA). The RDA analysis suggested that climate (temperature- and precipitation-related variables) and geography had similar magnitudes of effect in shaping the distribution of SNP genotypes across the sampled range of Murray cod. Although there was poor agreement among the candidate SNPs identified by the univariate methods, the top 5% of SNPs contributing to significant RDA axes included 67% of the SNPs identified by univariate methods. We discuss the potential implications of our findings for the management of Murray cod and other species generally, particularly in relation to informing conservation actions such as translocations to improve evolutionary resilience of natural populations. Our results highlight the value of using a combination of different approaches, including polygenic methods, when testing for signatures of adaptation in landscape genomic studies.
  8. Thai BT, Tan MH, Lee YP, Gan HM, Tran TT, Austin CM
    Mol Biol Rep, 2016 May;43(5):391-6.
    PMID: 26922181 DOI: 10.1007/s11033-016-3966-2
    The marine clam Lutraria rhynchaena is gaining popularity as an aquaculture species in Asia. Lutraria populations are present in the wild throughout Vietnam and several stocks have been established and translocated for breeding and aquaculture grow-out purposes. In this study, we demonstrate the feasibility of utilising Illumina next-generation sequencing technology to streamline the identification and genotyping of microsatellite loci from this clam species. Based on an initial partial genome scan, 48 microsatellite markers with similar melting temperatures were identified and characterised. The 12 most suitable polymorphic loci were then genotyped using 51 individuals from a population in Quang Ninh Province, North Vietnam. Genetic variation was low (mean number of alleles per locus = 2.6; mean expected heterozygosity = 0.41). Two loci showed significant deviation from Hardy-Weinberg equilibrium (HWE) and the presence of null alleles, but there was no evidence of linkage disequilibrium among loci. Three additional populations were screened (n = 7-36) to test the geographic utility of the 12 loci, which revealed 100 % successful genotyping in two populations from central Vietnam (Nha Trang). However, a second population from north Vietnam (Co To) could not be successfully genotyped and morphological evidence and mitochondrial variation suggests that this population represents a cryptic species of Lutraria. Comparisons of the Qang Ninh and Nha Trang populations, excluding the 2 loci out of HWE, revealed statistically significant allelic variation at 4 loci. We reported the first microsatellite loci set for the marine clam Lutraria rhynchaena and demonstrated its potential in differentiating clam populations. Additionally, a cryptic species population of Lutraria rhynchaena was identified during initial loci development, underscoring the overlooked diversity of marine clam species in Vietnam and the need to genetically characterise population representatives prior to microsatellite development. The rapid identification and validation of microsatellite loci using next-generation sequencing technology warrant its integration into future microsatellite loci development for key aquaculture species in Vietnam and more generally, aquaculture countries in the South East Asia region.
  9. Gan HM, Takahashi H, Hammer MP, Tan MH, Lee YP, Voss JM, et al.
    Mitochondrial DNA B Resour, 2017 Feb 06;2(1):73-75.
    PMID: 33473721 DOI: 10.1080/23802359.2017.1285206
    The complete mitochondrial genomes of four fish species of the commercially important family Latidae were sequenced using the Illumina MiSeq, thereby significantly increasing the mitogenomic resources for the family. Whole mitogenome-based phylogenetic analysis supports the monophyly of the genus Lates and more generally the family Latidae. The mitogenome sequences from this study will be useful for future assessments of the diversity within and between Lates species and studies of phylogenetic relationships within the diverse and taxonomically challenging perciform fishes.
  10. Tan MH, Gan HM, Lee YP, Austin CM
    Mitochondrial DNA A DNA Mapp Seq Anal, 2016 11;27(6):3981-3982.
    PMID: 25541307
    The mitochondrial genome sequence of the purple mottled shore crab, Cyclograpsus granulosus, is documented (GenBank accession number: LN624373), which makes it the third for genera of the superfamily Grapsoidea. Cyclograpsus granulosus has a mitogenome of 16,300 bp consisting of 13 protein-coding genes, two ribosomal subunit genes, 22 transfer RNAs and a non-coding AT-rich region. The base composition of the C. granulosus mitogenome is 36.15% for T, 19.54% for C, 33.14% for A and 11.17% for G, with an AT bias of 69.29%. The mitogenome gene order is atypical for the brachyuran crabs, but is identical to species of the genus Eriocheir from the same family.
  11. Tan MH, Gan HM, Lee YP, Austin CM
    Mitochondrial DNA A DNA Mapp Seq Anal, 2016 11;27(6):3983-3984.
    PMID: 25541305
    The mitochondrial genome sequence of the porcellanid crab, Petrolisthes haswelli is provided, making it the second for the family Porcellanidae and the third for the superfamily Galatheoidea. Petrolisthes haswelli has a mitogenome of 15,348 bp consisting of 13 protein-coding genes, two ribosomal subunit genes, 22 transfer RNAs and a non-coding AT-rich region. The base composition of the P. haswelli mitogenome is 35.66% for T, 18.65% for C, 34.35% for A and 11.34% for G, with an AT bias of 70.01%. The mitogenome gene order is identical to the mitogenome of Neopetrolisthes maculatus, the only other species of the family with a sequenced mitogenome.
  12. Tan MH, Gan HM, Lee YP, Austin CM
    PMID: 25423512 DOI: 10.3109/19401736.2014.982587
    The mitochondrial genome sequence of the ghost crab, Ocypode ceratophthalmus, is documented (GenBank accession number: LN611669) in this article. This is the first mitogenome for the family Ocypodidae and the second for the order Ocypodoidea. Ocypode ceratophthalmus has a mitogenome of 15,564 base pairs consisting of 13 protein-coding genes, two ribosomal subunit genes, 22 transfer RNAs and a non-coding AT-rich region. The base composition of the O. ceratophthalmus mitogenome is 35.78% for T, 19.36% for C, 33.73% for A and 11.13% for G, with an AT bias of 69.51% and the gene order is the typical arrangement for brachyuran crabs.
  13. Tan MH, Gan HM, Lee YP, Austin CM
    PMID: 25423510 DOI: 10.3109/19401736.2014.982585
    The Mictyris longicarpus (soldier crab) complete mitochondrial genome sequence is reported making it the first for the family Mictyridae and the second for the superfamily Ocypodoidea. The mitogenome is 15,548 base pairs made up of 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs and a non-coding AT-rich region. The soldier crab mitogenome gene order is characteristic of brachyuran crabs with a base composition of 36.58% for T, 19.15% for C, 32.43% for A and 11.83% for G, with an AT bias of 69.01%.
  14. Grandjean F, Tan MH, Gan HY, Gan HM, Austin CM
    PMID: 25738217 DOI: 10.3109/19401736.2015.1018207
    The Austropotamobius pallipes complete mitogenome has been recovered using Next-Gen sequencing. Our sample of A. pallipes has a mitogenome of 15,679 base pairs (68.44% A + T content) made up of 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs, and a 877 bp non-coding AT-rich region. This is the first mitogenome sequenced for a crayfish from the family Astacidae and the 4(th) for northern hemisphere genera.
  15. Lee YP, Gan HM, Tan MH, Lys I, Page R, Dias Wanigasekera B, et al.
    PMID: 25707411 DOI: 10.3109/19401736.2015.1018209
    The mitogenome of Paranephrops planifrons, was obtained by next generation sequencing. This crayfish has a mitochondrial genome of 16,174 base pairs with 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs (tRNA), and a non-coding AT-rich region of 771 bp. The P. planifrons nucleotide composition is: 33.63% for T, 21.92% for C, 34.46% for A, and 9.98% for G and has a 68.09% AT bias. While the mitogenome gene order for this species is consistent with aspects of the highly distinctive parastacid crayfish mitogenome gene arrangement, it has a novel gene order involving the rearrangements of a protein coding and several tRNA genes.
  16. Gan HM, Gan HY, Tan MH, Penny SS, Willan RC, Austin CM
    PMID: 25648928 DOI: 10.3109/19401736.2015.1007355
    The complete mitochondrial genome of the commercially and ecologically important and internationally vulnerable giant clam Tridacna squamosa was recovered by genome skimming using the MiSeq platform. The T. squamosa mitogenome has 20,930 base pairs (62.35% A+T content) and is made up of 12 protein-coding genes, 2 ribosomal subunit genes, 24 transfer RNAs, and a 2594 bp non-coding AT-rich region. The mitogenome has a relatively large insertion in the atp6 gene. This is the first mitogenome to be sequenced from the genus Tridacna, and the family Tridacnidae and represents a new gene order.
  17. Gan HM, Tan MH, Gan HY, Lee YP, Austin CM
    PMID: 25648918 DOI: 10.3109/19401736.2015.1007325
    The clawed lobster Nephrops norvegicus is an important commercial species in European waters. We have sequenced the complete mitochondrial genome of the species from a partial genome scan using Next-Gen sequencing. The N. norvegicus has a mitogenome of 16,132 base pairs (71.22% A+ T content) comprising 13 protein-coding genes, 2 ribosomal subunit genes, 21 transfer RNAs, and a putative 1259 bp non-coding AT-rich region. This mitogenome is the second fully characterized for the family Nephropidae and the first for the genus Nephrops. The mitogenome gene order is identical to the Maine lobster, Homarus americanus with the exception of the possible loss of the trnI gene.
  18. Gan HM, Gan HY, Lee YP, Grandjean F, Austin CM
    PMID: 25648916 DOI: 10.3109/19401736.2015.1007326
    The invasive freshwater crayfish Orconectes limosus mitogenome was recovered by genome skimming. The mitogenome is 16,223 base pairs in length consisting of 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs, and a non-coding AT-rich region. The O. limosus mitogenome has an AT bias of 71.37% and base composition of 39.8% for T, 10.3% for C, 31.5% for A, and 18.4% for G. The mitogene order is identical to two other genera of northern hemisphere crayfish that have been sequenced for this organelle.
  19. Gan HY, Gan HM, Lee YP, Austin CM
    Mitochondrial DNA A DNA Mapp Seq Anal, 2016 11;27(6):3985-3986.
    PMID: 25543913
    The complete mitochondrial genome of the Bass yabby Trypaea australiensis was obtained from a partial genome scan using the MiSeq sequencing system. The T. australiensis mitogenome is 16,821 bp in length (70.25% A + T content) made up of 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs and a putative 1977 bp non-coding AT-rich region. This Trypaea mitogenome sequence is the 5th for the family Callianassidae and represents a new gene order for the Decapoda involving protein-coding, rRNA and tRNA genes and the control region.
  20. Gan HY, Gan HM, Lee YP, Austin CM
    PMID: 25693708 DOI: 10.3109/19401736.2015.1007311
    The mitochondrial genome of the rock pool prawn (Palaemon serenus), is sequenced, making it the third for genera of the family Palaemonidae and the first for the genus Palaemon. The mitogenome is 15,967 base pairs in length and comprises 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs and a non-coding AT-rich region. The P. serenus mitogenome has an AT bias of 58.97% and a base composition of 29.79% for T, 24.14% for C, 29.18% for A, and 16.89% for G. The mitogenome gene order of P. serenus is identical to Exopalaemon carinicauda.
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