Horizontal functional gene transfer from bacteria to fishes

Genetic characterization, structural analysis, and detection of positive selection in small heat shock proteins of Cypriniformes and Clupeiformes

In the current investigation, a total of 42 full-length, non-redundant small heat shock proteins (sHsp) were detected in Cyprinus carpio, Labeo rohita, Danio rerio, Salmo salar, Oncorhynchus mykiss, and Clupea harengus. The sHsp genes were classified into three groups based on phylogenetic analysis. All the sHsps were shown to have higher aliphatic index values, which is an indication that these proteins are more thermally stable. The hydrophilic nature of sHsps was deduced from the fact that all fish species had negative GRAVY scores. In all of the representative fish species, sHsp genes were assigned to distinct chromosomes in an inconsistent and unequal manner. Segmental duplications are the main events that have contributed to the expansion of the sHsp genes in all species. We were also able to determine the selective pressure that was placed on particular codons and discovered several significant coding sites within the coding region of sHsps. Eventually, diversifying positive selection was found to be connected with evolutionary changes in sHsp proteins, which showed that gene evolution controlled the fish adaption event in response to environmental conditions. Clarification of the links between sHsps and environmental stress in fish will be achieved through rigorous genomic comparison, which will also yield substantial new insights.

Hybrids and horizontal transfer: introgression allows adaptive allele discovery

Evolution has devised countless remarkable solutions to diverse challenges. Understanding the mechanistic basis of these solutions provides insights into how biological systems can be subtly tweaked without maladaptive consequences. The knowledge gained from illuminating these mechanisms is equally important to our understanding of fundamental evolutionary mechanisms as it is to our hopes of developing truly rational plant breeding and synthetic biology. In particular, modern population genomic approaches are proving very powerful in the detection of candidate alleles for mediating consequential adaptations that can be tested functionally. Especially striking are signals gained from contexts involving genetic transfers between populations, closely related species, or indeed between kingdoms. Here we discuss two major classes of these scenarios, adaptive introgression and horizontal gene flow, illustrating discoveries made across kingdoms.

γ-Carboxymuconolactone decarboxylase: a novel cell cycle-related basal body protein in the early branching eukaryote Trichomonas vaginalis

BACKGROUND

γ-Carboxymuconolactone decarboxylase (CMD) participates in the β-ketoadipate pathway, which catalyzes aromatic compounds to produce acetyl- or succinyl-CoA, in prokaryotes and yeast. Our previous study demonstrated that expression of a CMD homologue that contains two signatures (dualCMD) is negatively regulated by iron in Trichomonas vaginalis. However, we were not able to identify the components of the β-ketoadipate pathway in the parasite's genome. These observations prompted us to investigate the biological functions of this novel CMD homologue in T. vaginalis.

METHODS

The specific anti-TvCMD1 antibody was generated, and the expression of TvCMD1 in T. vaginalis cultured under iron-rich and iron-deficient were evaluated. Phylogenetic, metabolomic and substrate induction (protocatechuate and benzoate) analysis were conducted to clarify the function of dualCMD in trichomonad cells. Subcellular localization of TvCMD1 was observed by confocal microscopy. The cell cycle-related role of TvCMD1 was assessed by treating cells with G2/M inhibitor nocodazole.

RESULTS

We confirmed that T. vaginalis is not able to catabolize the aromatic compounds benzoate and protocatechuate, which are known substrates of the β-ketoadipate pathway. Using immunofluorescence microscopy, we found that TvCMD1 is spatially associated with the basal body, a part of the cytoskeletal organizing center in T. vaginalis. TvCMD1 accumulated upon treatment with the G2/M inhibitor nocodazole. Additionally, TvCMD1 was expressed and transported to/from the basal body during cytokinesis, suggesting that TvCMD1 plays a role in cell division.

CONCLUSION

We demonstrated that TvCMD1 is unlikely to participate in the β-ketoadipate pathway and demonstrated that it is a novel basal body-localizing (associated) protein. This model sheds light on the importance of genes that are acquired laterally in the coevolution of ancient protists, which surprisingly functions in cell cycle regulation of T. vaginalis.

Antibiotic resistance genes (ARGs) in duck and fish production ponds with integrated or non-integrated mode

Antibiotic resistance genes (ARGs) are emerging micropollutants with environmental persistence. Aquaculture environments are considered as potential reservoirs for ARGs pollution and horizontal gene transfer (HGT). This study analyzed water and sediment from eight culture ponds (integrated culture: duck-fish pond; monoculture: duck pond and fish pond) and a control pond (without any aquaculture activity) in Zhongshan, South China. Seventeen types of ARGs were detected in all ponds, which conferring resistance to four classes of antibiotics including tetracycline (tetA, tetB, tetC, tetE, tetG, tetL, tetA-P, tetM, tetO, tetS, tetW and tetX), AmpC beta-lactamase products (EBC and FOX), sulfonamide (sul1 and sul2) and erythromycin (ermA), with class 1 integron (intI1) as motility gene. The total concentrations of detected ARGs in culture pond water were much higher than control (about 1.6-4.0 times). Integrated culture showed lowest absolute abundance of ∑ARGs in water (3.686 × 10⁷ copies mL^-1) and the highest in sediment (4.574 × 10⁸ copies g^-1). Monoculture ponds showed higher relative abundance of ∑ARGs both in water (fish pond: 0.5149) and sediment (duck pond: 0.4919). As the main contributor to the ARGs abundance and significant correlations with ∑tet, ∑ARGs and intI1 (P < 0.01), tetA was suggested to be a potential indicator for the abundance of tetracycline resistance genes in these classes of aquaculture modes in the Pearl River Delta. This study provides a case for the ARGs abundance in aquaculture and as a reference for the upcoming health risk assessment in aquatic environment.

Nothing in Evolution Makes Sense Except in the Light of Genomics: Read-Write Genome Evolution as an Active Biological Process

The 21st century genomics-based analysis of evolutionary variation reveals a number of novel features impossible to predict when Dobzhansky and other evolutionary biologists formulated the neo-Darwinian Modern Synthesis in the middle of the last century. These include three distinct realms of cell evolution; symbiogenetic fusions forming eukaryotic cells with multiple genome compartments; horizontal organelle, virus and DNA transfers; functional organization of proteins as systems of interacting domains subject to rapid evolution by exon shuffling and exonization; distributed genome networks integrated by mobile repetitive regulatory signals; and regulation of multicellular development by non-coding lncRNAs containing repetitive sequence components. Rather than single gene traits, all phenotypes involve coordinated activity by multiple interacting cell molecules. Genomes contain abundant and functional repetitive components in addition to the unique coding sequences envisaged in the early days of molecular biology. Combinatorial coding, plus the biochemical abilities cells possess to rearrange DNA molecules, constitute a powerful toolbox for adaptive genome rewriting. That is, cells possess "Read-Write Genomes" they alter by numerous biochemical processes capable of rapidly restructuring cellular DNA molecules. Rather than viewing genome evolution as a series of accidental modifications, we can now study it as a complex biological process of active self-modification.

Horizontal gene transfer events reshape the global landscape of arm race between viruses and homo sapiens

Horizontal gene transfer (HGT) drives the evolution of recipient organism particularly if it provides a novel function which enhances the fitness or its adaption to the environment. Virus-host co-evolution is attractive for studying co-evolutionary processes, since viruses strictly replicate inside of the host cells and thus their evolution is inexorably tangled with host biology. HGT, as a mechanism of co-evolution between human and viruses, has been widely documented, however, the roles HGT play during the interaction between human and viruses are still in their infancy. In this study, we performed a comprehensive analysis on the genes horizontally transferred between viruses and their corresponding human hosts. Our study suggests that the HGT genes in human are predominantly enriched in immune related GO terms while viral HGT genes are tend to be encoded by viruses which promote the invasion of immune system of hosts. Based on our results, it gives us a hint about the evolution trajectory of HGT events. Overall, our study suggests that the HGT between human and viruses are highly relevant to immune interaction and probably reshaped the arm race between hosts and viruses.

Detection of Prokaryotic Genes in the Amphimedon queenslandica Genome

Horizontal gene transfer (HGT) is common between prokaryotes and phagotrophic eukaryotes. In metazoans, the scale and significance of HGT remains largely unexplored but is usually linked to a close association with parasites and endosymbionts. Marine sponges (Porifera), which host many microorganisms in their tissues and lack an isolated germ line, are potential carriers of genes transferred from prokaryotes. In this study, we identified a number of potential horizontally transferred genes within the genome of the sponge, Amphimedon queenslandica. We further identified homologs of some of these genes in other sponges. The transferred genes, most of which possess catalytic activity for carbohydrate or protein metabolism, have assimilated host genome characteristics and are actively expressed. The diversity of functions contributed by the horizontally transferred genes is likely an important factor in the adaptation and evolution of A. queenslandica. These findings highlight the potential importance of HGT on the success of sponges in diverse ecological niches.