Tree Genome Research Articles

Metagenomic Next-Generation Sequencing Reveal Presence of a Novel Ungulate Bocaparvovirus in Alpacas.

Viruses belonging to the genus Bocaparvovirus (BoV) are a genetically diverse group of DNA viruses known to cause respiratory, enteric, and neurological diseases in animals, including humans. An intestinal sample from an alpaca (Vicugna pacos) herd with reoccurring diarrhea and respiratory disease was submitted for next-generation sequencing, revealing the presence of a BoV strain. The alpaca BoV strain (AlBoV) had a 58.58% whole genome nucleotide percent identity to a camel BoV from Dubai, belonging to a tentative ungulate BoV 8 species (UBoV8). Recombination events were lacking with other UBoV strains. The AlBoV genome was comprised of the NS1, NP1, and VP1 proteins. The NS1 protein had the highest amino acid percent identity range (57.89–67.85%) to the members of UBoV8, which was below the 85% cut-off set by the International Committee on Taxonomy of Viruses. The low NS1 amino acid identity suggests that AlBoV is a tentative new species. The whole genome, NS1, NP1, and VP1 phylogenetic trees illustrated distinct branching of AlBoV, sharing a common ancestor with UBoV8. Walker loop and Phospholipase A2 (PLA2) motifs that are vital for virus infectivity were identified in NS1 and VP1 proteins, respectively. Our study reports a novel BoV strain in an alpaca intestinal sample and highlights the need for additional BoV research.

Complete mitochondrial genome sequence of lettuce pathogenic fungus, Fusarium oxysporum f. sp. lactucae 16-086

Fusarium oxysporum f. sp. lactucae 016-086 is a plant pathogenic filamentous fungus isolated from wilted lettuce in Korea. We reported complete mitochondrial genome sequence of F. oxysporum f. sp. lactucae 016-086. Total length of this mitogenome is 41,826 bp and it encoded 42 genes (14 protein-coding genes, 2 rRNAs, and 26 tRNAs). Nucleotide sequence of coding region takes over 30.6%, and overall GC content is 32.5%. Phylogenetic tree of Fusarium mitochondrial genomes presented distinct clades along with nine formae speciales. This mitogenome will contribute distinguishing formae speciales of F. oxysoporum claearly with additional mitogenomes sequenced in the near future.

The complete mitochondrial genome of rockfish Sebastes oculatus Valenciennes, 1833 from southwest Atlantic ocean

The mitogenome of rockfish, Sebastes oculatus, has been determined for the first time. Assembled mitogenome was 16,767 bp in length, including 13 protein-coding genes, 22 transfer RNA and two ribosomal RNA genes as well as the non-coding region. The order and structure are the same as those of other Sebastes species. S. oculatus was sister to S. nigrocinctus and this clade is closely related with S. rubrivinctus, as well as support for previously published complete mitochondrial genome trees (Sandel et al. 2018). The mitogenome of S. oculatus provides significant DNA molecular data for further identification and phylogenetic analysis within Scorpaenid.

Phylogeny of Clostridium spp. Based on Conservative Genes and Comparisons with Other Trees

The genus Clostridium includes a group of anaerobic bacteria, which have remarkable application prospects in cellulose degradation and industrial production or are important pathogens. In this study, the phylogeny of Clostridium spp., whose complete genomes were reported, was inferred based on concatenation of 49 conservative genes, including ribosomal protein genes. The results indicated that the topology of the genomic tree was consistent with the clusters of the species in the ribosomal protein tree and 16S rRNA trees. Based on the alignment and phylogenetic analysis of 49 conservative selected genes and 27218 final nucleotide characters, the genomic tree supported classification results and reassignments of some species in previous works, including other genomic trees. The phylogenetic deduction was not only the classification skeleton of the genus Clostridium, but also the relationship of those species in genes involved in basic cell cycles.

Cyberinfrastructure to Improve Forest Health and Productivity: The Role of Tree Databases in Connecting Genomes, Phenomes, and the Environment.

Despite tremendous advancements in high throughput sequencing, the vast majority of tree genomes, and in particular, forest trees, remain elusive. Although primary databases store genetic resources for just over 2,000 forest tree species, these are largely focused on sequence storage, basic genome assemblies, and functional assignment through existing pipelines. The tree databases reviewed here serve as secondary repositories for community data. They vary in their focal species, the data they curate, and the analytics provided, but they are united in moving toward a goal of centralizing both data access and analysis. They provide frameworks to view and update annotations for complex genomes, interrogate systems level expression profiles, curate data for comparative genomics, and perform real-time analysis with genotype and phenotype data. The organism databases of today are no longer simply catalogs or containers of genetic information. These repositories represent integrated cyberinfrastructure that support cross-site queries and analysis in web-based environments. These resources are striving to integrate across diverse experimental designs, sequence types, and related measures through ontologies, community standards, and web services. Efficient, simple, and robust platforms that enhance the data generated by the research community, contribute to improving forest health and productivity.

Rapid evolution of \u03b1-gliadin gene family revealed by analyzing Gli-2 locus regions of wild emmer wheat

α-Gliadins are a major group of gluten proteins in wheat flour that contribute to the end-use properties for food processing and contain major immunogenic epitopes that can cause serious health-related issues including celiac disease (CD). α-Gliadins are also the youngest group of gluten proteins and are encoded by a large gene family. The majority of the gene family members evolved independently in the A, B, and D genomes of different wheat species after their separation from a common ancestral species. To gain insights into the origin and evolution of these complex genes, the genomic regions of the Gli-2 loci encoding α-gliadins were characterized from the tetraploid wild emmer, a progenitor of hexaploid bread wheat that contributed the AABB genomes. Genomic sequences of Gli-2 locus regions for the wild emmer A and B genomes were first reconstructed using the genome sequence scaffolds along with optical genome maps. A total of 24 and 16 α-gliadin genes were identified for the A and B genome regions, respectively. α-Gliadin pseudogene frequencies of 86% for the A genome and 69% for the B genome were primarily caused by C to T substitutions in the highly abundant glutamine codons, resulting in the generation of premature stop codons. Comparison with the homologous regions from the hexaploid wheat cv. Chinese Spring indicated considerable sequence divergence of the two A genomes at the genomic level. In comparison, conserved regions between the two B genomes were identified that included α-gliadin pseudogenes containing shared nested TE insertions. Analyses of the genomic organization and phylogenetic tree reconstruction indicate that although orthologous gene pairs derived from speciation were present, large portions of α-gliadin genes were likely derived from differential gene duplications or deletions after the separation of the homologous wheat genomes ~ 0.5 MYA. The higher number of full-length intact α-gliadin genes in hexaploid wheat than that in wild emmer suggests that human selection through domestication might have an impact on α-gliadin evolution. Our study provides insights into the rapid and dynamic evolution of genomic regions harboring the α-gliadin genes in wheat.

A fossil-calibrated phylogenomic analysis of Daphnia and the Daphniidae

In the post-genomic era, much of phylogenetic analyses still relies on mitochondrial DNA, either alone or in combination with few nuclear genes. Although this approach often makes it possible to construct well-supported trees, it is limited because mtDNA describes the history of a single locus, and nuclear phylogenies based on a few loci may be biased, leading to inaccurate tree topologies and biased estimations of species divergence time. In this study, we perform a phylogenomic analysis of the Daphniidae family (Crustacea: Branchiopoda: Anomopoda) including some of the most frequently studied model organisms (Daphnia magna and D. pulex) whose phylogenetic relationships have been based primarily on an assessment of a few mtDNA genes. Using high-throughput sequencing, we were able to assemble 38 whole mitochondrial genomes and draft nuclear genomes for 18 species, including at least one species for each known genus of the family Daphniidae. Here we present phylogenies based on 636 nuclear single-copy genes shared among all sampled taxa and based on whole mtDNA genomes. The phylogenies we obtained were highly supported and showed some discrepancies between nuclear and mtDNA based trees at deeper nodes. We also identified a new candidate sister lineage of Daphnia magna. Our time-calibrated genomic trees, which we constructed using both fossil records and substitution rates, yielded very different estimates of branching event times compared to those based on mtDNA. By providing multi-locus, fossil-calibrated trees of the Daphniidae, our study contributes to an improved phylogenetic framework for ecological and evolutionary studies that use water fleas as a model system.

Developing Blight-Tolerant American Chestnut Trees.

An invasive fungal pathogen has reduced the American chestnut (Castanea dentata), once a keystone tree species within its natural range in the eastern United States and Canada, to functional extinction. To help restore this important canopy tree, blight-tolerant American chestnut trees have been developed using an oxalate oxidase-encoding gene from wheat. This enzyme breaks down oxalate, which is produced by the pathogen and forms killing cankers. Expressing oxalate oxidase results in blight tolerance, where the tree and the fungus can coexist, which is a more evolutionarily stable relationship than direct pathogen resistance. Genetic engineering (GE) typically makes a very small change in the tree's genome, potentially avoiding incompatible gene interactions that have been detected in some chestnut hybrids. The GE American chestnut also retains all the wild American chestnut's alleles for habitat adaptation, which are important for a forest ecosystem restoration program.

Comparative Analysis of the Two Acinetobacter baumannii Multilocus Sequence Typing (MLST) Schemes.

Acinetobacter species assigned to the Acinetobacter calcoaceticus-baumannii (Acb) complex, are Gram-negative bacteria responsible for a large number of human infections. The population structure of Acb has been studied using two 7-gene MLST schemes, introduced by Bartual and coworkers (Oxford scheme) and by Diancourt and coworkers (Pasteur scheme). The schemes have three genes in common but underlie two coexisting nomenclatures of sequence types and clonal complexes, which complicates communication on A. baumannii genotypes. The aim of this study was to compare the characteristics of the two schemes to make a recommendation about their usage. Using genome sequences of 730 strains of the Acb complex, we evaluated the phylogenetic congruence of MLST schemes, the correspondence between sequence types, their discriminative power and genotyping reliability from genomic sequences. In silico ST re-assignments highlighted the presence of a second copy of the Oxford gdhB locus, present in 553/730 genomes that has led to the creation of artefactual profiles and STs. The reliability of the two MLST schemes was tested statistically comparing MLST-based phylogenies to two reference phylogenies (core-genome genes and genome-wide SNPs) using topology-based and likelihood-based tests. Additionally, each MLST gene fragment was evaluated by correlating the pairwise nucleotide distances between each pair of genomes calculated on the core-genome and on each single gene fragment. The Pasteur scheme appears to be less discriminant among closely related isolates, but less affected by homologous recombination and more appropriate for precise strain classification in clonal groups, which within this scheme are more often correctly monophyletic. Statistical tests evaluate the tree deriving from the Oxford scheme as more similar to the reference genome trees. Our results, together with previous work, indicate that the Oxford scheme has important issues: gdhB paralogy, recombination, primers sequences, position of the genes on the genome. While there is no complete agreement in all analyses, when considered as a whole the above results indicate that the Pasteur scheme is more appropriate for population biology and epidemiological studies of A. baumannii and related species and we propose that it should be the scheme of choice during the transition toward, and in parallel with, core genome MLST.

New Insights into Long Terminal Repeat Retrotransposons in Mulberry Species.

The evolutionary dynamics of long terminal repeat (LTR) retrotransposons in tree genomes has remained largely unknown. The availability of the complete genome sequences of the mulberry tree (Morus notabilis) has offered an unprecedented opportunity for us to characterize these retrotransposon elements. We investigated 202 and 114 families of Copia and Gypsy superfamilies, respectively, comprising 2916 intact elements in the mulberry genome. The tRNAMet was the most frequently used type of tRNA in both superfamilies. Phylogenetic analysis suggested that Copia and Gypsy from mulberry can be grouped into eight and six lineages, respectively. All previously characterized families of such elements could also be found in the mulberry genome. About 95% of the identified Copia and Gypsy full elements were estimated to have been inserted into the mulberry genome within the past 2–3 million years. Meanwhile, the estimated insertion times of members of the three most abundant families of the Copia superfamily (908 members from the three most abundant families) and Gypsy superfamily (783 members from the three most abundant families) revealed divergent life histories. Compared with the situation in Gypsy elements, three families of Copia elements are under positive selection pressure, which suggested that Copia elements may have a dominant influence in the evolution of mulberry genes. Analysis of insertion and deletion dynamics suggested that Copia and Gypsy elements exhibited a very long half-life in the mulberry genome. The present work provides new insights into the insertion and deletion dynamics of LTR retrotransposons, and it will greatly improve our understanding of the important roles transposable elements play in the architecture of the mulberry genome.

Genomes of skipper butterflies reveal extensive convergence of wing patterns

For centuries, biologists have used phenotypes to infer evolution. For decades, a handful of gene markers have given us a glimpse of the genotype to combine with phenotypic traits. Today, we can sequence entire genomes from hundreds of species and gain yet closer scrutiny. To illustrate the power of genomics, we have chosen skipper butterflies (Hesperiidae). The genomes of 250 representative species of skippers reveal rampant inconsistencies between their current classification and a genome-based phylogeny. We use a dated genomic tree to define tribes (six new) and subtribes (six new), to overhaul genera (nine new) and subgenera (three new), and to display convergence in wing patterns that fooled researchers for decades. We find that many skippers with similar appearance are distantly related, and several skippers with distinct morphology are close relatives. These conclusions are strongly supported by different genomic regions and are consistent with some morphological traits. Our work is a forerunner to genomic biology shaping biodiversity research.

A high-density genetic map and QTL mapping on growth and latex yield-related traits in Hevea brasiliensis Müll.Arg

Hevea brasiliensis Müll.Arg., the rubber tree, is an important industrial crop, which is the major source of nature rubber. Recently, Simple Sequence Repeat (SSR)- and Single Nucleotide Polymorphism (SNP)-based genetic maps have been reported, however further trait-related markers are needed for efficient molecular breeding in rubber tree. In this study, a total of 206 F1 progeny derived from a cross of CATAS 8–79 × MT/C/11 9/67 were sequenced and genotyped by specific–locus amplified fragment sequencing (SLAF-seq) technology. Based on 268,592 SNPs obtained from SLAF-seq, a high-density genetic map with 4,543 SNPs was constructed, covering 2,670.27 cM of the whole rubber tree genome. This map has an average marker distance of 0.59 cM.Based on the high-density genetic map, dynamic quantitative trait loci (QTL) analysis of latex yield and stem growth was carried out by conditional and unconditional QTL mapping. To our knowledge, it is the first time to perform conditional QTL mapping of rubber tree for exploring QTLs expressed selectively at different growth stages. In total, eleven QTLs for stem growth and 12 QTLs for latex yield, distributing in 15 linkage groups (LGs), were detected, explaining 3.1%–18.4% of the phenotypic variance. Two QTLs, qSG-8-2 for stem growth and qLD-8-3 for latex yield, were mapped within the same marker interval of LG 8 with a genetic distance of 3.0 cM. Herein the high-density genetic map and trait-related QTLs in rubber tree were reported, which will facilitate the genetic research of rubber tree and enhance rubber tree molecular breeding.

Phylogenetic analysis of integrases of Acinetobacter baumannii genomic islands

Acinetobacter baumannii among other pathogens is capable of acquiring new virulence determinants via mobile genetic elements (MGE). Analysis of the distribution of genomic islands (GIs) has shown in many species that most MGEs cluster tightly with specific lineages on a phylogenetic core genome tree. This study aims to address the questions on the association between GIs distribution among certain clonal lineagesand to test the contribution of G08 and G62 in A. baumannii to metal susceptibility phenotypes. The whole genome phylogenetic single nucleotide polymorphism (SNP) tree was build using the feature frequency profile. As input, the 101 complete A. baumannii genomes deposited in GenBank were used. The matrix was generated using command line blast and the R platform to generate the output. Susceptibility testing of heavy metals was performed on wild-type and GI-deletion mutants using eight different heavy metals. Whole genome phylogenetic SNP tree constructed on all complete deposited A. baumannii genomes showed that the integrase of the metal resistance G08 and G62 are present only in single or very few sequence types (STs). To test the hypothesis that these GI seven if present only in defined lineage are still mobile, G08 and G62 were selected respectively in strains AB0057 and ATCC17978. Phylogenetic analysis of the respective GI integrases confirmed that the G08int and G62int belong to a separate clade within the Acinetobacter tyrosine recombinases. Susceptibility testing in A. baumannii strain ATCC 17978, AB0057 and their respective ΔG62 and ΔG08 mutants confirmed the contribution of the GI-encoded efflux transporters to heavy metal decreased susceptibility.

Selection and validation of suitable reference genes for RT-qPCR analysis in dove tree (Davidia involucrata Baill.)

Fifteen candidate reference genes were selected from the dove tree genome. Their performance as internal controls for RT-qPCR analysis was assessed in bracts at different developmental stages, normal and abortive seeds, and leaves of different colors. The applicability of the candidate reference genes was validated through detection of the expression levels of three target genes normalized by different reference genes. Dove tree (Davidia) is a relic species and has some unique traits in its reproductive organs. The molecular mechanisms underlying the development of these organs have attracted increasing attention. RT-qPCR is a powerful tool for gene expression pattern detection, which is critical for studies on gene function or regulation. However, information regarding suitable reference genes, which ensures reliable RT-qPCR results, is absent in dove tree. Based on our previously obtained Davidia transcriptome data, 15 reference genes, including eight traditional and seven novel reference genes, were selected for this study. Using geNorm, NormFinder and BestKeeper software, the stability and applicability of these candidate reference genes were assessed with regard to different aspects including bract development, seed abortion and leaf color. The candidate reference genes were ranked by the software programs, and the most suitable and unsuitable genes for different situations were determined. In addition, the expression levels of three Davidia genes of interest involved in bract development, seed abortion and leaf color, respectively, were normalized with high-ranking and low-ranking reference genes. The comparison results demonstrated that the selection of “good” or “bad” reference genes led to differing conclusions.

BIOBOARD

Asia-Pacific — New bid to stamp out bowel cancer. Asia-Pacific — New way to breach blood-brain barrier when treating brain cancer. Asia-Pacific — New antibiotic to fight deadly superbug in large intestine. Asia-Pacific — Revealing the secrets of rogue clones which cause Lupus disease. Asia-Pacific — Stout camphor tree genome sequence completed. Rest of the World — Newly established Center for Neurodegenerative Diseases in Hong Kong. Rest of the World — New approach to sepsis therapy.

Analyses of four new Caulobacter Phicbkviruses indicate independent lineages.

Bacteriophages with genomes larger than 200 kbp are considered giant phages, and the giant Phicbkviruses are the most frequently isolated Caulobacter crescentus phages. In this study, we compare six bacteriophage genomes that differ from the genomes of the majority of Phicbkviruses. Four of these genomes are much larger than those of the rest of the Phicbkviruses, with genome sizes that are more than 250 kbp. A comparison of 16 Phicbkvirus genomes identified a 'core genome' of 69 genes that is present in all of these Phicbkvirus genomes, as well as shared accessory genes and genes that are unique for each phage. Most of the core genes are clustered into the regions coding for structural proteins or those involved in DNA replication. A phylogenetic analysis indicated that these 16 CaulobacterPhicbkvirus genomes are related, but they represent four distinct branches of the Phicbkvirus genomic tree with distantly related branches sharing little nucleotide homology. In contrast, pairwise comparisons within each branch of the phylogenetic tree showed that more than 80 % of the entire genome is shared among phages within a group. This conservation of the genomes within each branch indicates that horizontal gene transfer events between the groups are rare. Therefore, the Phicbkvirus genus consists of at least four different phylogenetic branches that are evolving independently from one another. One of these branches contains a 27-gene inversion relative to the other three branches. Also, an analysis of the tRNA genes showed that they are relatively mobile within the Phicbkvirus genus.

Complete mitochondrial genome sequence of the food fermentation fungus, Aspergillus luchuensis

Aspergillus luchuensis is a filamentous fungus used for food and alcohol fermentation in many Asian countries. Here, we reported the complete mitochondrial genome sequence of A. luchuensis isolated from fermented soybean brick, called as Meju, in Korea. Its mitochondrial genome was successfully assembled from raw reads sequenced using MiSeq by Velvet and GapCloser. Total length of the mitochondrial genome is 31,228 bp and encoded 44 genes (16 protein-coding genes, two rRNAs, and 26 tRNAs). Nucleotide sequence of coding region takes over 25.6%, and overall GC content is 26.4%. Phylogenetic tree of mitochondrial genomes presented A. luchuensis and Aspergillus kawachii are clustered in one clade. This mitochondrial genome can be used for further analyses of Aspergillus mitochondrial comparative genomics to improve understanding of diverse Aspergillus species.

Eucalyptus grandis THIOREDOXINS, DIVERSITY AND GENE EXPRESSION

ABSTRACT Tree genomes have been sequenced in recent years providing a source of basic information on multigenic family characterization. Comparative genomics based on those complete genome sequences available in public database is an important tool providing useful information to progress on functional gene characterization. In this work, we focus on gene encoding for Thioredoxins (Trxs) in Eucalyptus grandis genome, which are oxidoreductase enzymes, involved in significant biochemical processes, above all the maintenance of cellular homeostasis. Here we investigate the diversity, structure and expression of these genes in eucalyptus. For this purpose, bioinformatics tools were employed, using public platforms data, to identify coding sequences and validate gene expression. Specific softwares were employed to characterize gene structure and expression. RT-PCR assays were carried out to specifically verify the expression of 4 cytoplasmic thioredoxin genes, observed in silico from leaf, phloem, xylem and apical meristem tissues. Twenty-two Trxs with characteristic and canonic active sites were identified, confirming the presence of all types of the three main groups already defined as plastidial (m, f, x, y, z) cytoplasmatic (h) and mitochondrial (o). However, differences in the number of genes per group were observed when compared with other tree genomes. The expression of these thioredoxin genes compared to some homologous genes presented divergent expression patterns compared to Arabidopis thaliana suggesting a functional specificity in eucalyptus, such as in the case of Eucgr.F01604 gene encoding an h1 cytoplasmic Trx, which presents a strong expression in conductor tissues.

Stout camphor tree genome fills gaps in understanding of flowering plant genome evolution

We present reference-quality genome assembly and annotation for the stout camphor tree (Cinnamomum kanehirae (Laurales, Lauraceae)), the first sequenced member of the Magnoliidae comprising four orders (Laurales, Magnoliales, Canellales and Piperales) and over 9,000 species. Phylogenomic analysis of 13 representative seed plant genomes indicates that magnoliid and eudicot lineages share more recent common ancestry than monocots. Two whole-genome duplication events were inferred within the magnoliid lineage: one before divergence of Laurales and Magnoliales and the other within the Lauraceae. Small-scale segmental duplications and tandem duplications also contributed to innovation in the evolutionary history of Cinnamomum. For example, expansion of the terpenoid synthase gene subfamilies within the Laurales spawned the diversity of Cinnamomum monoterpenes and sesquiterpenes.

Genomic technologies for Hevea breeding.

The commercial production of high quality natural rubber (NR) solely depends on Hevea brasiliensis Muell. Arg, (Para rubber tree) and accounts for >98% of total production worldwide. NR with its unique properties is an essential commodity for the automobile industry and its synthetic counterparts are in no way substitute to it. The rubber tree genome is very complex and plays an important role in delivering the unique properties of Hevea. But a lack of knowledge on the molecular mechanisms of rubber biosynthesis, disease resistance, etc., in elite clones of rubber still persists. Marker-assisted selection and transgenic techniques were proved to be advantageous in improving the breeding efficiency for latex yield, disease resistance, etc. The suppression subtractive hybridization (SSH), in the form of subtracted cDNA libraries and microarrays, can assist in searching the functions of expressed genes (candidate gene approach). Expressed sequence tags (ESTs) related to various metabolic aspects are well utilized to create EST banks that broadly represent the genes expressed in one tissue, such as latex cells, that assists in the study of gene function and regulation. Transcriptome analysis and gene mapping have been accomplished in Hevea at various stages. However, a selection criterion to delineate high yielding genotypes at the juvenile stage has not been accomplished so far. This is the main pit fall for rubber breeding apart from stock-scion interactions leading to yield differences among a clonally multiplied population. At least four draft genome sequences have been published on Hevea rubber, and all give different genome size and contig lengths-a comprehensive and acceptable genomic map remains unfulfilled. The progress made in molecular markers, latex biosynthesis genes, transcriptome analysis, chloroplast and mitochondrial DNA diversity, paternity identification through Breeding without Breeding (BwB), stimulated latex production and its molecular intricacies, molecular biology of tapping panel dryness, genomics for changed climates and genome mapping are discussed in this review. These information can be utilized to improvise the molecular breeding programs of Hevea in future.