RESUMO

Factors that increase reproductive variance among individuals act to reduce effective population size (Ne), which accelerates the loss of genetic diversity and decreases the efficacy of purifying selection. These factors include sexual cannibalism, offspring investment and mating system. Pre-copulatory sexual cannibalism, where the female consumes the male prior to mating, exacerbates this effect. We performed comparative transcriptomics in two spider species, the cannibalistic Trechaleoides biocellata and the non-cannibalistic T. keyserlingi, to generate genomic evidence to support these predictions. First, we estimated heterozygosity and found that genetic diversity is relatively lower in the cannibalistic species. Second, we calculated dN/dS ratios as a measure of purifying selection; a higher dN/dS ratio indicated relaxed purifying selection in the cannibalistic species. These results are consistent with the hypothesis that sexual cannibalism impacts operational sex ratio and demographic processes, which interact with evolutionary forces to shape the genetic structure of populations. However, other factors such as the mating system and life-history traits contribute to shaping Ne. Comparative analyses across multiple contrasting species pairs would be required to disentangle these effects. Our study highlights that extreme behaviours such as pre-copulatory cannibalism may have profound eco-evolutionary effects.

Assuntos

RESUMO

Lipoxygenases (LOXs) are enzymes that catalyze the addition of an oxygen molecule to unsaturated fatty acids, thus forming hydroperoxides. In plants, these enzymes are encoded by a multigene family found in several organs with varying activity patterns, by which they are classified as LOX9 or LOX13. They are involved in several physiological functions, such as growth, fruit development, and plant defense. Despite several studies on genes of the LOX family in plants, most studies are restricted to a single species or a few closely related species. This study aimed to analyze the diversity, evolution, and expression of LOX genes in angiosperm species. We identified 247 LOX genes among 23 species of angiosperms and basal plants. Phylogenetic analyses identified clades supporting LOX13 and two main clades for LOX9: LOX9_A and LOX9_B. Eudicot species such as Tarenaya hassleriana, Capsella rubella, and Arabidopsis thaliana did not present LOX9_B genes; however, LOX9_B was present in all monocots used in this study. We identified that there were potential new subcellular localization patterns and conserved residues of oxidation for LOX9 and LOX13 yet unexplored. In summary, our study provides a basis for the further functional and evolutionary study of lipoxygenases in angiosperms.

RESUMO

The human Respiratory Syncytial Virus (hRSV) is the main causative agent of acute respiratory infections (ARI), such as pneumonia and bronchiolitis. One of the factors that lead to success in viral replication is the interaction of the M2-2 protein with the ribosomal complex. This interaction is responsible for the phase change of viral activity, acting as an inhibitor or inducer of viral replication, according to the concentration of mRNA. Based on the importance of M2-2 gene and protein have to viral physiology, we performed here evaluations of genetic diversity, phylogenetic reconstructions, phylodynamics, and selection test. Our results suggested an alternative way of classifying this virus in clades A and B, based on a new phylogenetic marker, the M2-2 gene. Therefore, our study is the first one to investigate the dynamics of the evolutionary diversification process of hRSV from the perspective of the M2-2 viral gene. In our study was also identified that the M2-2 gene is under the effect of purifying selection originated by population genetic bottlenecks. Therefore, the M2-2 gene demonstrated an interesting potential to be applied in evolutionary studies involving hRSV, recovering phylogenetic signals and traits of natural selection under the evolution of this virus.

Assuntos

RESUMO

"Junk DNA" is a popular yet controversial concept that states that organisms carry in their genomes DNA that has no positive impact on their fitness. Nonetheless, biochemical functions have been identified for an increasing fraction of DNA elements traditionally seen as "Junk DNA". These findings have been interpreted as fundamentally undermining the "Junk DNA" concept. Here, we reinforce previous arguments that this interpretation relies on an inadequate concept of biological function that does not consider the selected effect of a given genomic structure, which is central to the "Junk DNA" concept. Next, we suggest that another (though ignored) confounding factor is that the discussion about biological functions includes two different dimensions: a horizontal, ecological dimension that reflects how a given genomic element affects fitness in a specific time, and a vertical, temporal dimension that reflects how a given genomic element persisted along time. We suggest that "Junk DNA" should be used exclusively relative to the horizontal dimension, while for the vertical dimension, we propose a new term, "Spam DNA", that reflects the fact that a given genomic element may persist in the genome even if not selected for on their origin. Importantly, these concepts are complementary. An element can be both "Spam DNA" and "Junk DNA", and "Spam DNA" can also be recruited to perform evolved biological functions, as illustrated in processes of exaptation or constructive neutral evolution.

Assuntos

RESUMO

BACKGROUND: The 'Zacatuche', 'Teporingo', or Volcano rabbit (Romerolagus diazi) belongs to the family Leporidae, is an endemic species restricted to the Central part of the Trans-Mexican Volcanic Belt, and is considered 'endangered' by the IUCN Red List of Threatened Species. METHODS AND RESULTS: This study reports, for the first time, the complete mitochondrial genome of R. diazi and examined the phylogenetic position of R. diazi among other closely related co-familiar species using mitochondrial protein-coding genes (PCGs). The mitogenome of R. diazi was assembled from short Illumina 150 bp pair-end reads with a coverage of 189x. The AT-rich mitochondrial genome of R. diazi is 17,400 bp in length and is comprised of 13 PCGs, two ribosomal RNA genes, and 22 transfer RNA genes. The gene order observed in the mitochondrial genome of R. diazi is identical to that reported for other leporids. Phylogenetic analyses based on PCGs support the basal position of Romerolagus within the Leporidae, at least when compared to the genera Oryctolagus and Lepus. Nonetheless, additional mitochondrial genomes from species belonging to the genera Bunolagus, Sylvilagus, and Pronolagus, among others, are needed before a more robust conclusion about the derived vs basal placement of Romerolagus within the family Leporidae can be reached based on mitochondrial PCGs. CONCLUSIONS: This is the first genomic resource developed for R. diazi and it represents a tool to improve our understanding about the ecology and evolutionary biology of this iconic and endangered species.

Assuntos

RESUMO

Severe bottlenecks significantly diminish the amount of genetic diversity and the speed at which it accumulates (i.e., evolutionary rate). They further compromise the efficiency of natural selection to eliminate deleterious variants, which may reach fixation in the surviving populations. Consequently, expanding and adapting to new environments may pose a significant challenge when strong bottlenecks result in genetic pauperization. Herein, we surveyed the patterns of nucleotide diversity, molecular adaptation and genetic load across 177 gene-loci in a circum-Mediterranean conifer (Pinus pinea L.) that represents one of the most extreme cases of genetic pauperization in widespread outbreeding taxa. We found very little genetic variation in both hypervariable nuclear microsatellites (SSRs) and gene-loci, which translated into genetic diversity estimates one order of magnitude lower than those previously reported for pines. Such values were consistent with a strong population decline that began some ~1 Ma. Comparisons with the related and parapatric maritime pine (Pinus pinaster Ait.) revealed reduced rates of adaptive evolution (α and ωa ) and a significant accumulation of genetic load. It is unlikely that these are the result from differences in mutation rate or linkage disequilibrium between the two species; instead they are the presumable outcome of contrasting demographic histories affecting both the speed at which these taxa accumulate genetic diversity, and the global efficacy of selection. Future studies, and programs for conservation and management, should thus start testing for the effects of genetic load on fitness, and integrating such effects into predictive models.

Assuntos

RESUMO

Among members of the Bacillales order, there are several species capable of forming a structure called an endospore. Endospores enable bacteria to survive under unfavourable growth conditions and germinate when environmental conditions are favourable again. Spore-coat proteins are found in a multilayered proteinaceous structure encasing the spore core and the cortex. They are involved in coat assembly, cortex synthesis and germination. Here, we aimed to determine the diversity and evolutionary processes that have influenced spore-coat genes in various spore-forming species of Bacillales using an in silico approach. For this, we used sequence similarity searching algorithms to determine the diversity of coat genes across 161 genomes of Bacillales. The results suggest that among Bacillales, there is a well-conserved core genome, composed mainly by morphogenetic coat proteins and spore-coat proteins involved in germination. However, some spore-coat proteins are taxa-specific. The best-conserved genes among different species may promote adaptation to changeable environmental conditions. Because most of the Bacillus species harbour complete or almost complete sets of spore-coat genes, we focused on this genus in greater depth. Phylogenetic reconstruction revealed eight monophyletic groups in the Bacillus genus, of which three are newly discovered. We estimated the selection pressures acting over spore-coat genes in these monophyletic groups using classical and modern approaches and detected horizontal gene transfer (HGT) events, which have been further confirmed by scanning the genomes to find traces of insertion sequences. Although most of the genes are under purifying selection, there are several cases with individual sites evolving under positive selection. Finally, the HGT results confirm that sporulation is an ancestral feature in Bacillus.

Assuntos

RESUMO

Terpenoids are a diverse class of metabolites that impact plant metabolism in response to environmental cues. They are synthesized either via a predominantly cytosolic (MVA) pathway or a plastidic pathway (MEP). In Arabidopsis, several enzymes from the MVA and MEP pathways are encoded by gene families, excluding MVK and DXR, which are single-copy genes. In this study, we assess the diversity, evolution and expression of DXR and MVK genes in selected angiosperms and Coffea arabica in particular. Evolutionary analysis revealed that DXR and MVK underwent purifying selection, but the selection effect for DXR was stronger than it was for MVK. Digital gene expression (DGE) profile analysis of six species revealed that expression levels of MVK in flowers and roots were high, whereas for DXR peak values were observed in leaves. In C. arabica, both genes were highly expressed in flowers, and CaDXR was upregulated in response to methyl jasmonate. C. arabica DGE data were validated by assessing gene expression in selected organs, and by plants treated with hexanoic acid (Hx) using RT-qPCR. MVK expression was upregulated in roots treated with Hx. CaDXR was downregulated in leaves by Hx treatment in a genotype-specific manner, indicating a differential response to priming.

RESUMO

The WFDC1 gene is frequently down-regulated or lost in prostate cancer, and the encoded protein, ps20, has been implicated in epithelial cell behaviour and angiogenesis. However, ps20 remains largely uncharacterised with respect to its structure and interacting partners. This study characterised the evolution, functionality and structural characteristics of WFDC1/ps20 using phylogenetic reconstruction and other computational approaches. Bayesian phylogenetic analyses suggested that ps20 appeared in a common ancestor of deuterostomes-protostomes. The rate of evolutionary change within the coding regions of vertebrate WFDC1 genes and the synteny conservation in mammals differed from that of other vertebrate clades, indicating a possible functional diversity of ps20 homologues. A gene set enrichment analysis of the genes around WFDC1 (conserved synteny) showed functional relationships between the WFDC1, CDH13, CRISPLD2, IRF8 and TFPI2 genes. The molecular evolution of ps20 has been driven by purifying selection, particularly in the segments corresponding to exons 3 and 4, which encode the most conserved regions of the protein. A co-evolution analysis showed that residues within these regions co-vary with each other during the evolution of ps20. These results show that the regions corresponding to exons 3 and 4 are ps20-specific structure-function modules. Homology modelling of the exon 2-encoded polypeptide and subsequent dynamics calculus using a Gaussian network model showed that residues with high conformational flexibility are part of a loop region involved in protein-protein recognition, given the similarity with other serine protease inhibitors. Residues C96, R94, L105, and C66 are critical for the integrity and functionality of this ps20 region.

Assuntos

RESUMO

To be able to survive, Helicobacter pylori must adhere to the gastric epithelial cells of its human host. For this purpose, the bacterium employs an array of adhesins, for example, AlpA. The adhesin AlpA has been proposed as a major adhesin because of its critical role in human stomach colonization. Therefore, understanding how AlpA evolved could be important for the development of new diagnostic strategies. However, the genetic variation and microevolutionary patterns of alpA have not been described in Colombia. The study aim was to describe the variation patterns and microevolutionary process of alpA in Colombian clinical isolates of H. pylori. The existing polymorphisms, which are deviations from the neutral model of molecular evolution, and the genetic differentiation of the alpA gene from Colombian clinical isolates of H. pylori were determined. The analysis shows that gene conversion and purifying selection have shaped the evolution of three different variants of alpA in Colombia.

RESUMO

BACKGROUND: Whole-genome duplication (WGD) events have shaped the genomes of eukaryotic organisms. Relaxed selection after duplication along with inherent functional constraints are thought to determine the fate of the paralogs and, ultimately, the evolution of gene function. Here, we investigated the rate of protein evolution (as measured by dN/dS ratios) before and after the WGD in the hemiascomycete yeasts, and the way in which changes in such rates relate to molecular and biological function. RESULTS: For most groups of orthologous genes (81%) we observed a change in the rates of evolution after genome duplication. Genes with atypically-low dN/dS ratio before the WGD were prone to increase their rates of evolution after duplication. Importantly, the paralogs were often different in their rates of evolution after the WGD (50% cases), however, this was more consistent with an asymmetric deceleration in the protein-evolution rates, rather than an asymmetric increase of the initial rates. Functional-category analysis showed that regulatory proteins such as protein kinases and transcription factors were enriched in genes that increase their rates of evolution after the WGD. While changes in the rate of protein-sequence evolution were associated to protein abundance, content of disordered regions, and contribution to fitness, these features were an attribute of specific functional classes. CONCLUSIONS: Our results indicate that strong purifying selection in ancestral pre-duplication sequences is a strong predictor of increased rates after the duplication in yeasts and that asymmetry in evolution rate is established during the deceleration phase. In addition, changes in the rates at which paralogous sequences evolve before and after WGD are different for specific protein functions; increased rates of protein evolution after duplication occur preferentially in specific protein functions.

Assuntos

RESUMO

Cichlid fishes are an ideal model system for studying biological diversification because they provide textbook examples of rapid speciation. To date, there has been little focus on the role of gene regulation during cichlid speciation. However, in recent years, gene regulation has been recognized as a powerful force linking diversification in gene function to speciation. Here, we investigated the potential role of miRNA regulation in the diversification of six cichlid species of the Midas cichlid lineage (Amphilophus spp.) inhabiting the Nicaraguan crater lakes. Using several genomic resources, we inferred 236 Midas miRNA genes that were used to predict the miRNA target sites on 8,232 Midas 3'-UTRs. Using population genomic calculations of SNP diversity, we found the miRNA genes to be more conserved than protein coding genes. In contrast to what has been observed in other cichlid fish, but similar to what has been typically found in other groups, we observed genomic signatures of purifying selection on the miRNA targets by comparing these sites with the less conserved nontarget portion of the 3'-UTRs. However, in one species pair that has putatively speciated sympatrically in crater Lake Apoyo, we recovered a different pattern of relaxed purifying selection and high genetic divergence at miRNA targets. Our results suggest that sequence evolution at miRNA binding sites could be a critical genomic mechanism contributing to the rapid phenotypic evolution of Midas cichlids.

Assuntos

RESUMO

Sigma factors are an essential part of bacterial gene regulation and have been extensively studied as far as their molecular mechanisms and protein structure are concerned. However, their molecular evolution, especially for the alternative sigma factors, is poorly understood. Here, we analyze the evolutionary forces that have shaped the rpoH sigma factors within the alphaproteobacteria. We found that an ancient duplication gave rise to two major groups of rpoH sigma factors and that after this event horizontal gene transfer (HGT) occurred in rpoH 1 group. We also noted that purifying selection has differentially affected distinct parts of the gene; singularly, the gene segment that encodes the region 4.2, which interacts with the -35 motif of the RpoH-dependent genes, has been under relaxed purifying selection. Furthermore, these two major groups are clearly differentiated from one another regarding their promoter selectivity, as rpoH 1 is under the transcriptional control of σ(70) and σ(32), whereas rpoH 2 is under the transcriptional control of σ(24). Our results suggest a scenario in which HGT, gene loss, variable purifying selection and clear promoter specialization occurred after the ancestral duplication event. More generally, our study offers insights into the molecular evolution of alternative sigma factors and highlights the importance of analyzing not only the coding regions but also the promoter regions.

RESUMO

Sporothrix schenckii sensu lato causes subcutaneous mycosis. In this article we analysed its phylogeny and genetic diversity using calmodulin DNA sequences deposited in GenBank database. Population genetics indices were calculated, plus phylogenetic and haplotype network trees were built. Five clades with high values of posterior probability, 47 haplotypes and high diversity in the complex were found. Analysis of partial calmodulin sequences alignment revealed conserved and polymorphic regions that could be used as reference for taxonomic identification. The use of population genetics analysis allowed understanding the phylogenetic proximity of S. schenckii s. str. and S. brasiliensis; scarce genetic flow among them with low migration index and high ancestry coefficient was found. Similarly, S. globosa, S. mexicana and S. pallida sequences showed highly differentiated species with no genetic exchange. The phylogenetic tree suggests that S. mexicana shared a common ancestor with S. pallida; while S. globosa and S. brasiliensis are more related to S. schenckii s. str. and showed less haplotype diversity and restrictions in geographic distribution. In the haplotype network tree S. schenckii s. str. species displayed worldwide distribution without dispersion centres; while S. brasiliensis and S. globosa, exhibited Brazil and Euro-Asia as dispersion centres, respectively. Our data suggest that S. schenckii complex has been submitted to a divergent evolution process, probably due to the pressure of the environment and of the host. In contrast, S. brasiliensis could have been submitted to purifying selection or expansion process.

Assuntos