Metaxa : a software tool for automated detection and discrimination among ribosomal small subunit (12S/16S/18S) sequences of archaea, bacteria, eukaryotes, mitochondria, and chloroplasts in metagenomes and environmental sequencing datasets

Peer reviewedPostprin

Current trends in chloroplast genome research

Chloroplast is an important cellular organelle of autotrophs which has an independent, circular, doublestranded DNA molecule termed as chloroplast genome. The chloroplast DNA (cpDNA) contains essential genes for its maintenance and operation. Several components of the photosystems andproteins involved in biosynthetic pathways are also encoded by the chloroplast genome. Exploring the genetic repository of this organelle is vital due to its conserved nature, small size, persistent gene organization and promising ability for transgenic expression. Therefore, cpDNA sequence information has been instrumental in phylogenetic studies and molecular taxonomy of plants. Chloroplast genome sequencing efforts have being initiated with conventional cloning and chain-termination sequencing technologies. Dedicated databases such as CGDB and GOBASE among others have been established as more and more complete cpDNA sequences are being reported. Presently, elegant molecular biologytechniques including shotgun sequencing, rolling circle amplification (RCA), Amplification, Sequencing and Annotation of Plasteome (ASAP) and Next generation sequencing are being used to accelerate data output. Owing to many fold increase in submission of cpDNA sequences in nucleotide databases, challenges of in-depth data analysis stimulated the emergence of devoted annotation, assembling and phylogenetic software. Recently, reported bioinformatics software for chloroplast genome studiescomprise of DOGMA for annotation, SCAN-SE, ARAGON and PREP suit for RNA analyses and CG viewer for circular map construction/comparative analysis. Faster algorithms for gene-order based phylogenetic reconstruction and bootstrap analysis have attracted the attention of research community. Current trends in sequencing strategies and bioinformatics with reference to chloroplast genomes hold great potential to illuminate more hidden corners of this ancient cell organelle

REDIdb: the RNA editing database

The RNA Editing Database (REDIdb) is an interactive, web-based database created and designed with the aim to allocate RNA editing events such as substitutions, insertions and deletions occurring in a wide range of organisms. The database contains both fully and partially sequenced DNA molecules for which editing information is available either by experimental inspection (in vitro) or by computational detection (in silico). Each record of REDIdb is organized in a specific flat-file containing a description of the main characteristics of the entry, a feature table with the editing events and related details and a sequence zone with both the genomic sequence and the corresponding edited transcript. REDIdb is a relational database in which the browsing and identification of editing sites has been simplified by means of two facilities to either graphically display genomic or cDNA sequences or to show the corresponding alignment. In both cases, all editing sites are highlighted in colour and their relative positions are detailed by mousing over. New editing positions can be directly submitted to REDIdb after a user-specific registration to obtain authorized secure access. This first version of REDIdb database stores 9964 editing events and can be freely queried at

Mitome: dynamic and interactive database for comparative mitochondrial genomics in metazoan animals

Mitome is a specialized mitochondrial genome database designed for easy comparative analysis of various features of metazoan mitochondrial genomes such as base frequency, A+T skew, codon usage and gene arrangement pattern. A particular function of the database is the automatic reconstruction of phylogenetic relationships among metazoans selected by a user from a taxonomic tree menu based on nucleotide sequences, amino acid sequences or gene arrangement patterns. Mitome also enables us (i) to easily find the taxonomic positions of organisms of which complete mitochondrial genome sequences are publicly available; (ii) to acquire various metazoan mitochondrial genome characteristics through a graphical genome browser; (iii) to search for homology patterns in mitochondrial gene arrangements; (iv) to download nucleotide or amino acid sequences not only of an entire mitochondrial genome but also of each component; and (v) to find interesting references easily through links with PubMed. In order to provide users with a dynamic, responsive, interactive and faster web database, Mitome is constructed using two recently highlighted techniques, Ajax (Asynchronous JavaScript and XML) and Web Services. Mitome has the potential to become very useful in the fields of molecular phylogenetics and evolution and comparative organelle genomics. The database is available at: http://www.mitome.info

Database for bacterial group II introns

The Database for Bacterial Group II Introns (http://webapps2.ucalgary.ca/~groupii/index.html#) provides a catalogue of full-length, non-redundant group II introns present in bacterial DNA sequences in GenBank. The website is divided into three sections. The first section provides general information on group II intron properties, structures and classification. The second and main section lists information for individual introns, including insertion sites, DNA sequences, intron-encoded protein sequences and RNA secondary structure models. The final section provides tools for identification and analysis of intron sequences. These include a step-by-step guide to identify introns in genomic sequences, a local BLAST tool to identify closest intron relatives to a query sequence, and a boundary-finding tool that predicts 5′ and 3′ intron–exon junctions in an input DNA sequence. Finally, selected intron data can be downloaded in FASTA format. It is hoped that this database will be a useful resource not only to group II intron and RNA researchers, but also to microbiologists who encounter these unexpected introns in genomic sequences

The Rhodomonas salina mitochondrial genome: bacteria-like operons, compact gene arrangement and complex repeat region

To gain insight into the mitochondrial genome structure and gene content of a putatively ancestral group of eukaryotes, the cryptophytes, we sequenced the complete mitochondrial DNA of Rhodomonas salina. The 48 063 bp circular-mapping molecule codes for 2 rRNAs, 27 tRNAs and 40 proteins including 23 components of oxidative phosphorylation, 15 ribosomal proteins and two subunits of tat translocase. One potential protein (ORF161) is without assigned function. Only two introns occur in the genome; both are present within cox1 belong to group II and contain RT open reading frames. Primitive genome features include bacteria-like rRNAs and tRNAs, ribosomal protein genes organized in large clusters resembling bacterial operons and the presence of the otherwise rare genes such as rps1 and tatA. The highly compact gene organization contrasts with the presence of a 4.7 kb long, repeat-containing intergenic region. Repeat motifs ∼40–700 bp long occur up to 31 times, forming a complex repeat structure. Tandem repeats are the major arrangement but the region also includes a large, ∼3 kb, inverted repeat and several potentially stable ∼40–80 bp long hairpin structures. We provide evidence that the large repeat region is involved in replication and transcription initiation, predict a promoter motif that occurs in three locations and discuss two likely scenarios of how this highly structured repeat region might have evolved

ChloroMitoSSRDB 2.00: More genomes, more repeats, unifying SSRs search patterns and on-the-fly repeat detection

© The Author(s) 2015. Published by Oxford University Press. Organelle genomes evolve rapidly as compared with nuclear genomes and have been widely used for developing microsatellites or simple sequence repeats (SSRs) markers for delineating phylogenomics. In our previous reports, we have established the largest repository of organelle SSRs, ChloroMitoSSRDB, which provides access to 2161 organelle genomes (1982 mitochondrial and 179 chloroplast genomes) with a total of 5838 perfect chloroplast SSRs, 37 297 imperfect chloroplast SSRs, 5898 perfect mitochondrial SSRs and 50 355 imperfect mitochondrial SSRs across organelle genomes. In the present research, we have updated ChloroMitoSSRDB by systematically analyzing and adding additional 191 chloroplast and 2102 mitochondrial genomes. With the recent update, ChloroMitoSSRDB 2.00 provides access to a total of 4454 organelle genomes displaying a total of 40 653 IMEx Perfect SSRs (11 802 Chloroplast Perfect SSRs and 28 851 Mitochondria Perfect SSRs), 275 981 IMEx Imperfect SSRs (78 972 Chloroplast Imperfect SSRs and 197 009 Mitochondria Imperfect SSRs), 35 250 MISA (MIcroSAtellite identification tool) Perfect SSRs and 3211 MISA Compound SSRs and associated information such as location of the repeats (coding and non-coding), size of repeat, motif and length polymorphism, and primer pairs. Additionally, we have integrated and made available several in silico SSRs mining tools through a unified web-portal for in silico repeat mining for assembled organelle genomes and from next generation sequencing reads. ChloroMitoSSRDB 2.00 allows the end user to perform multiple SSRs searches and easy browsing through the SSRs using two repeat algorithms and provide primer pair information for identified SSRs for evolutionary genomics

The complete chloroplast DNA sequence of the green alga Oltmannsiellopsis viridis reveals a distinctive quadripartite architecture in the chloroplast genome of early diverging ulvophytes

BACKGROUND: The phylum Chlorophyta contains the majority of the green algae and is divided into four classes. The basal position of the Prasinophyceae has been well documented, but the divergence order of the Ulvophyceae, Trebouxiophyceae and Chlorophyceae is currently debated. The four complete chloroplast DNA (cpDNA) sequences presently available for representatives of these classes have revealed extensive variability in overall structure, gene content, intron composition and gene order. The chloroplast genome of Pseudendoclonium (Ulvophyceae), in particular, is characterized by an atypical quadripartite architecture that deviates from the ancestral type by a large inverted repeat (IR) featuring an inverted rRNA operon and a small single-copy (SSC) region containing 14 genes normally found in the large single-copy (LSC) region. To gain insights into the nature of the events that led to the reorganization of the chloroplast genome in the Ulvophyceae, we have determined the complete cpDNA sequence of Oltmannsiellopsis viridis, a representative of a distinct, early diverging lineage. RESULTS: The 151,933 bp IR-containing genome of Oltmannsiellopsis differs considerably from Pseudendoclonium and other chlorophyte cpDNAs in intron content and gene order, but shares close similarities with its ulvophyte homologue at the levels of quadripartite architecture, gene content and gene density. Oltmannsiellopsis cpDNA encodes 105 genes, contains five group I introns, and features many short dispersed repeats. As in Pseudendoclonium cpDNA, the rRNA genes in the IR are transcribed toward the single copy region featuring the genes typically found in the ancestral LSC region, and the opposite single copy region harbours genes characteristic of both the ancestral SSC and LSC regions. The 52 genes that were transferred from the ancestral LSC to SSC region include 12 of those observed in Pseudendoclonium cpDNA. Surprisingly, the overall gene organization of Oltmannsiellopsis cpDNA more closely resembles that of Chlorella (Trebouxiophyceae) cpDNA. CONCLUSION: The chloroplast genome of the last common ancestor of Oltmannsiellopsis and Pseudendoclonium contained a minimum of 108 genes, carried only a few group I introns, and featured a distinctive quadripartite architecture. Numerous changes were experienced by the chloroplast genome in the lineages leading to Oltmannsiellopsis and Pseudendoclonium. Our comparative analyses of chlorophyte cpDNAs support the notion that the Ulvophyceae is sister to the Chlorophyceae

Transcriptomics and molecular evolutionary rate analysis of the bladderwort (Utricularia), a carnivorous plant with a minimal genome

<p>Abstract</p> <p>Background</p> <p>The carnivorous plant <it>Utricularia gibba </it>(bladderwort) is remarkable in having a minute genome, which at ca. 80 megabases is approximately half that of <it>Arabidopsis</it>. Bladderworts show an incredible diversity of forms surrounding a defined theme: tiny, bladder-like suction traps on terrestrial, epiphytic, or aquatic plants with a diversity of unusual vegetative forms. <it>Utricularia </it>plants, which are rootless, are also anomalous in physiological features (respiration and carbon distribution), and highly enhanced molecular evolutionary rates in chloroplast, mitochondrial and nuclear ribosomal sequences. Despite great interest in the genus, no genomic resources exist for <it>Utricularia</it>, and the substitution rate increase has received limited study.</p> <p>Results</p> <p>Here we describe the sequencing and analysis of the <it>Utricularia gibba </it>transcriptome. Three different organs were surveyed, the traps, the vegetative shoot bodies, and the inflorescence stems. We also examined the bladderwort transcriptome under diverse stress conditions. We detail aspects of functional classification, tissue similarity, nitrogen and phosphorus metabolism, respiration, DNA repair, and detoxification of reactive oxygen species (ROS). Long contigs of plastid and mitochondrial genomes, as well as sequences for 100 individual nuclear genes, were compared with those of other plants to better establish information on molecular evolutionary rates.</p> <p>Conclusion</p> <p>The <it>Utricularia </it>transcriptome provides a detailed genomic window into processes occurring in a carnivorous plant. It contains a deep representation of the complex metabolic pathways that characterize a putative minimal plant genome, permitting its use as a source of genomic information to explore the structural, functional, and evolutionary diversity of the genus. Vegetative shoots and traps are the most similar organs by functional classification of their transcriptome, the traps expressing hydrolytic enzymes for prey digestion that were previously thought to be encoded by bacteria. Supporting physiological data, global gene expression analysis shows that traps significantly over-express genes involved in respiration and that phosphate uptake might occur mainly in traps, whereas nitrogen uptake could in part take place in vegetative parts. Expression of DNA repair and ROS detoxification enzymes may be indicative of a response to increased respiration. Finally, evidence from the bladderwort transcriptome, direct measurement of ROS <it>in situ</it>, and cross-species comparisons of organellar genomes and multiple nuclear genes supports the hypothesis that increased nucleotide substitution rates throughout the plant may be due to the mutagenic action of amplified ROS production.</p