Comparative genome analyses of deuterostomes: Metabolism and base composities of tunicates, fish and mammals genomes

The hypothesis that the metabolic rate could affect the base composition of genomes, i.e. the GC content, was tested along the phylogenetic line of deuterostomes, in the classes of tunicates, fish and mammals, by different approaches dictated by available data. Significant differences were found between the GC content of the completely sequenced genomes of C.intestinalis and C.savignyi. Interestingly, the increment was higher in C.savignyi in coding and non-coding regions, and mainly at the third codon positions (7% GC3). Methylation process and substitution rate were checked if responsible of the observed differences. The frequencies of CpG, CpA and TpG were no different between the two tunicates, and (even if tunicates showed a substitution rate 50% faster than that of vertebrates) the base composition was not directly affected. Multivariate analysis on codon usages showed that: i) in both species selection acts on codon usage, shaping translationally preferred codons between highly and lowly expressed genes; and ii) gene expression level affects the GC content of the two tunicate genomes. Data on the metabolic rate and the average genomic GC content were available for more than 200 teleostean species. Analyzing data according to the habitats, significant differences were found, with polar fish characterized by the highest metabolic rate and by a high GC content. A significant correlation was found between the two variables. Finally, intra-genome analyses of functional classes in more than ten mammalian genomes, confirmed the link between metabolism and GC content. In each mammalian genome, indeed, the average GC3 level was higher in genes involved in "metabolic processes". The same genome organization was not found in amphibians and reptiles, characterized by lower metabolic rates than mammals. The various approaches converged towards a coherent picture, highlighting the importance of metabolic rate as a factor shaping the base composition of genome

The elusive mitochondrial genomes of Apicomplexa: where are we now?

Mitochondria are vital organelles of eukaryotic cells, participating in key metabolic pathways such as cellular respiration, thermogenesis, maintenance of cellular redox potential, calcium homeostasis, cell signaling, and cell death. The phylum Apicomplexa is entirely composed of obligate intracellular parasites, causing a plethora of severe diseases in humans, wild and domestic animals. These pathogens include the causative agents of malaria, cryptosporidiosis, neosporosis, East Coast fever and toxoplasmosis, among others. The mitochondria in Apicomplexa has been put forward as a promising source of undiscovered drug targets, and it has been validated as the target of atovaquone, a drug currently used in the clinic to counter malaria. Apicomplexans present a single tubular mitochondria that varies widely both in structure and in genomic content across the phylum. The organelle is characterized by massive gene migrations to the nucleus, sequence rearrangements and drastic functional reductions in some species. Recent third generation sequencing studies have reignited an interest for elucidating the extensive diversity displayed by the mitochondrial genomes of apicomplexans and their intriguing genomic features. The underlying mechanisms of gene transcription and translation are also ill-understood. In this review, we present the state of the art on mitochondrial genome structure, composition and organization in the apicomplexan phylum revisiting topological and biochemical information gathered through classical techniques. We contextualize this in light of the genomic insight gained by second and, more recently, third generation sequencing technologies. We discuss the mitochondrial genomic and mechanistic features found in evolutionarily related alveolates, and discuss the common and distinct origins of the apicomplexan mitochondria peculiarities

How Fast Is the Sessile Ciona?

Genomewide analyses of distances between orthologous gene pairs from the ascidian species Ciona intestinalis and Ciona savignyi were compared with those of vertebrates. Combining this data with a detailed and careful use of vertebrate fossil records, we estimated the time of divergence between the two ascidians nearly 180 My. This estimation was obtained after correcting for the different substitution rates found comparing several groups of chordates; indeed we determine here that on average Ciona species evolve 50% faster than vertebrates

The footprint of metabolism in the organization of mammalian genomes

<p>Abstract</p> <p>Background</p> <p>At present five evolutionary hypotheses have been proposed to explain the great variability of the genomic GC content among and within genomes: the mutational bias, the biased gene conversion, the DNA breakpoints distribution, the thermal stability and the metabolic rate. Several studies carried out on bacteria and teleostean fish pointed towards the critical role played by the environment on the metabolic rate in shaping the base composition of genomes. In mammals the debate is still open, and evidences have been produced in favor of each evolutionary hypothesis. Human genes were assigned to three large functional categories (as well as to the corresponding functional classes) according to the KOG database: (i) information storage and processing, (ii) cellular processes and signaling, and (iii) metabolism. The classification was extended to the organisms so far analyzed performing a reciprocal Blastp and selecting the best reciprocal hit. The base composition was calculated for each sequence of the whole CDS dataset.</p> <p>Results</p> <p>The GC3 level of the above functional categories was increasing from (i) to (iii). This specific compositional pattern was found, as footprint, in all mammalian genomes, but not in frog and lizard ones. Comparative analysis of human versus both frog and lizard functional categories showed that genes involved in the metabolic processes underwent the highest GC3 increment. Analyzing the KOG functional classes of genes, again a well defined intra-genomic pattern was found in all mammals. Not only genes of metabolic pathways, but also genes involved in chromatin structure and dynamics, transcription, signal transduction mechanisms and cytoskeleton, showed an average GC3 level higher than that of the whole genome. In the case of the human genome, the genes of the aforementioned functional categories showed a high probability to be associated with the chromosomal bands.</p> <p>Conclusions</p> <p>In the light of different evolutionary hypotheses proposed so far, and contributing with different potential to the genome compositional heterogeneity of mammalian genomes, the one based on the metabolic rate seems to play not a minor role. Keeping in mind similar results reported in bacteria and in teleosts, the specific compositional patterns observed in mammals highlight metabolic rate as unifying factor that fits over a wide range of living organisms.</p

Genome Sequence of the Native Apiculate Wine Yeast Hanseniaspora vineae T02/19AF

The use of novel yeast strains for winemaking improves quality and provides variety including subtle characteristic differences in fine wines. Here we report the first genome of a yeast strain native to Uruguay, Hanseniaspora vineae T02/19AF, which has been shown to positively contribute to aroma and wine quality.Fil: Giorello, Facundo M.. Universidad de la República; UruguayFil: Berná, Luisa. Instituto Pasteur de Montevideo; UruguayFil: Greif, Gonzalo. Instituto Pasteur de Montevideo; UruguayFil: Camesasca, Laura. Inst. de Investigaciones Biológicas Clemente Estable; UruguayFil: Salzman, Valentina. Instituto Pasteur de Montevideo; Uruguay. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Medina, Karina. Universidad de la Republica. Facultad de Química; UruguayFil: Robello, Carlos. Instituto Pasteur de Montevideo; UruguayFil: Gaggero, Carina. Inst. de Investigaciones Biológicas Clemente Estable; UruguayFil: Aguilar, Pablo S.. Instituto Pasteur de Montevideo; UruguayFil: Carrau, Francisco. Sección Enología; Urugua

Biology of the <em>Trypanosoma cruzi</em> Genome

The genome of Trypanosoma cruzi was first made available in 2005, and the intrinsic genome complexity of this parasite has hindered high-quality genome assembly and annotation. Recent technological developments in long read sequencing allowed to circumvent this problem, showing very interesting features in the genome architecture of T. cruzi, allowing to accurately estimate gene copy numbers, abundance and distribution of repetitive sequences (including satellites and retroelements), and the complexity of multigene families implied in host-parasite interactions. The genome of T. cruzi is composed of a “core compartment” and a “disruptive compartment” which exhibit opposite GC content and gene composition, with high differences on their regulatory regions. The novel tandem and dispersed repetitive sequences identified, in addition to recombination events, allows to conclude that genome plasticity is a key survival strategy during its complex life cycle

Reevaluation of the Toxoplasma gondii and Neospora caninum genomes reveals misassembly, karyotype differences, and chromosomal rearrangements

Neospora caninum primarily infects cattle, causing abortions, with an estimated impact of a billion dollars on the worldwide economy annually. However, the study of its biology has been unheeded by the established paradigm that it is virtually identical to its close relative, the widely studied human pathogen Toxoplasma gondii. By revisiting the genome sequence, assembly, and annotation using third-generation sequencing technologies, here we show that the N. caninum genome was originally incorrectly assembled under the presumption of synteny with T. gondii. We show that major chromosomal rearrangements have occurred between these species. Importantly, we show that chromosomes originally named Chr VIIb and VIII are indeed fused, reducing the karyotype of both N. caninum and T. gondii to 13 chromosomes. We reannotate the N. caninum genome, revealing more than 500 new genes. We sequence and annotate the nonphotosynthetic plastid and mitochondrial genomes and show that although apicoplast genomes are virtually identical, high levels of gene fragmentation and reshuffling exist between species and strains. Our results correct assembly artifacts that are currently widely distributed in the genome database of N. caninum and T. gondii and, more importantly, highlight the mitochondria as a previously oversighted source of variability and pave the way for a change in the paradigm of synteny, encouraging rethinking the genome as basis of the comparative unique biology of these pathogens.INIA: FSSA_X_2014_1_10602

New insights into phenotype and genotype relationships in Neospora caninum

The successful isolation of four new Neospora caninum strains from different regions and with different backgrounds (obtained from an abortion storm or congenitally infected and asymptomatic calves) allowed us previously to characterize natural isolates, finding differences in phenotype and microsatellites. Given the variability observed, we wondered in this work whether these differences had consequences in virulence, invasion and vertical transmission using cell cultures and murine neosporosis models. In addition, we performed the genomic analysis and SNP comparative studies of the NcURU isolates. The results obtained in this work allowed us to establish that NcURU isolates are of low virulence and have unique phenotypic characteristics. Likewise, sequencing their genomes has allowed us to delve into the genetic singularities underlying these phenotypes, as well as the common mutated genes. This work opens a new perspective for diagnostic purposes and formulating possible vaccines based on attenuated strains

Comparative genomics of drug‑resistant strains of Mycobacterium tuberculosis in Ecuador

Background: Tuberculosis is a serious infectious disease affecting millions of people. In spite of efforts to reduce the disease, increasing antibiotic resistance has contributed to persist in the top 10 causes of death worldwide. In fact, the increased cases of multi (MDR) and extreme drug resistance (XDR) worldwide remains the main challenge for tuberculosis control. Whole genome sequencing is a powerful tool for predicting drug resistance‑related variants, studying lineages, tracking transmission, and defining outbreaks. This study presents the identification and characterization of resistant clinical isolates of Mycobacterium tuberculosis including a phylogenetic and molecular resistance profile study by sequencing the complete genome of 24 strains from different provinces of Ecuador. Results: Genomic sequencing was used to identify the variants causing resistance. A total of 15/21 isolates were identified as MDR, 4/21 as pre‑XDR and 2/21 as XDR, with three isolates discarded due to low quality; the main sub‑lineage was LAM (61.9%) and Haarlem (19%) but clades X, T and S were identified. Of the six pre‑XDR and XDR strains, it is noteworthy that five come from females; four come from the LAM sub‑lineage and two correspond to the X‑class sub‑lineage. A core genome of 3,750 genes, distributed in 295 subsystems, was determined. Among these, 64 proteins related to virulence and implicated in the pathogenicity of M. tuberculosis and 66 possible pharmacological targets stand out. Most variants result in nonsynonymous amino acid changes and the most frequent genotypes were identified as conferring resistance to rifampicin, isoniazid, ethambutol, para‑aminosalicylic acid and streptomycin. However, an increase in the resistance to fluoroquinolones was detected. Conclusion: This work shows for the first time the variability of circulating resistant strains between men and women in Ecuador, highlighting the usefulness of genomic sequencing for the identification of emerging resistance. In this regard, we found an increase in fluoroquinolone resistance. Further sampling effort is needed to determine the total variability and associations with the metadata obtained to generate better health policies

Maxicircle architecture and evolutionary insights into Trypanosoma cruzi complex

We sequenced maxicircles from T. cruzi strains representative of the species evolutionary diversity by using long-read sequencing, which allowed us to uncollapse their repetitive regions, finding that their real lengths range from 35 to 50 kb. T. cruzi maxicircles have a common architecture composed of four regions: coding region (CR), AT-rich region, short (SR) and long repeats (LR). Distribution of genes, both in order and in strand orientation are conserved, being the main differences the presence of deletions affecting genes coding for NADH dehydrogenase subunits, reinforcing biochemical findings that indicate that complex I is not functional in T. cruzi. Moreover, the presence of complete minicircles into maxicircles of some strains lead us to think about the origin of minicircles. Finally, a careful phylogenetic analysis was conducted using coding regions of maxicircles from up to 29 strains, and 1108 single copy nuclear genes from all of the DTUs, clearly establishing that taxonomically T. cruzi is a complex of species composed by group 1 that contains clades A (TcI), B (TcIII) and D (TcIV), and group 2 (1 and 2 do not coincide with groups I and II described decades ago) containing clade C (TcII), being all hybrid strains of the BC type. Three variants of maxicircles exist in T. cruzi: a, b and c, in correspondence with clades A, B, and C from mitochondrial phylogenies. While A and C carry maxicircles a and c respectively, both clades B and D carry b maxicircle variant; hybrid strains also carry the b- variant. We then propose a new nomenclature that is self-descriptive and makes use of both the phylogenetic relationships and the maxicircle variants present in T. cruzi