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Novel Freshwater Cyanophages Provide New Insights into Evolutionary Relationships between Freshwater and Marine Cyanophages.

ABSTRACT: Cyanobacteria and cyanophages are present widely in both freshwater and marine environments. However, freshwater cyanophages remain unknown largely due to the small numbers of cyanophage isolates despite their ecological and environmental significance. In this study, we present the characterization of two novel lytic freshwater cyanophages isolated from a tropical inland lake in Singapore, namely, cyanopodovirus S-SRP01 and cyanomyovirus S-SRM01, infecting two different strains of Synechococcus spp. Functional annotation of S-SRP01 and S-SRM01 genomes revealed a high degree of homology with marine cyanophages. Phylogenetic trees of concatenated genes and whole-genome alignment provided further evidence that S-SRP01 is close evolutionarily to marine cyanopodoviruses, while S-SRM01 is evolutionarily close to marine cyanomyoviruses. Few genetic similarities between freshwater and marine cyanophages have been identified in previous studies. The isolation of S-SRP01 and S-SRM01 expand current knowledge on freshwater cyanophages infecting Synechococcus spp. Their high degree of gene sharing provides new insights into the evolutionary relationships between freshwater and marine cyanophages. This relatedness is further supported by the discovery of similar phenomenon from other freshwater viral metagenomes. IMPORTANCE This study expands the current knowledge on freshwater cyanophage isolates and cyanophage genetic diversity, indicating that freshwater and marine cyanophages infecting Synechococcus spp. may share close genetic similarity and evolutionary relationships.

SUBMITTER: Zhang D

PROVIDER: S-EPMC8557907 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundAcross the tree of life there are numerous evolutionary transitions between different habitats (i.e., aquatic and terrestrial or marine and freshwater). Many of these dramatic evolutionary shifts parallel developmental shifts that require physiological, anatomical and behavioral changes for survival and reproduction. Diadromy (scheduled movement between marine and freshwater) has been characterized as a behavior that acts as an evolutionary intermediate state between marine and freshwater environments, implying that diadromous lineages are evolutionarily transient. This hypothesis comes with assumptions regarding the rates of evolutionary transitions in and out of diadromy as well as rates of speciation and extinction in diadromous fishes.ResultsBased on a published phylogeny of 7822 species of ray-finned fishes, state speciation and extinction models of evolutionary transition between marine, freshwater, and diadromous species suggest transition rates out of diadromy are 5-100 times higher that transition between marine and freshwater or into diadromy. Additionally, high speciation and low extinction rates separate diadromous fishes from marine and freshwater species. As a result, net diversification (net diversification = speciation - extinction) is about 7-40 times higher in diadromous fishes compared to freshwater and marine respectively. Together the transition, speciation, and extinction rates suggest diadromy is the least stable of the three states.ConclusionEvolutionary transitions to diadromy are rare in fishes. However, once established, diversification rates in diadromous lineages are high compared to both marine and freshwater species. Diadromous lineages tend to be more transient than marine or freshwater lineages and are found to give rise to marine and freshwater specialists in addition to diadromous descendants. Although diadromy is not a necessary evolutionary intermediate between marine and freshwater, these results support the interpretation of diadromy as an important, occasionally intermediate state, that contributes to biodiversity in fishes in all environments. This evolutionary instability of diadromous lineages is counteracted by their relatively high diversification rates. These findings highlight the importance of integrating the dynamics of diversification and major evolutionary transitions for understanding macroevolutionary patterns.

Project description:Genome sequencing is a powerful tool to understand species evolutionary history, uncover genes under selection, which could be informative of local adaptation, and infer measures of genetic diversity, inbreeding and mutational load that could be used to inform conservation efforts. Gorillas, critically endangered primates, have received considerable attention and with the recently sequenced Bwindi mountain gorilla population, genomic data is now available from all gorilla subspecies and both mountain gorilla populations. Here, we reanalysed this rich dataset with a focus on evolutionary history, local adaptation and genomic parameters relevant for conservation. We estimate a recent split between western and eastern gorillas of 150,000-180,000 years ago, with gene flow around 20,000 years ago, primarily between the Cross River and Grauer's gorilla subspecies. This gene flow event likely obscures evolutionary relationships within eastern gorillas: after excluding putatively introgressed genomic regions, we uncover a sister relationship between Virunga mountain gorillas and Grauer's gorillas to the exclusion of Bwindi mountain gorillas. This makes mountain gorillas paraphyletic. Eastern gorillas are less genetically diverse and more inbred than western gorillas, yet we detected lower genetic load in the eastern species. Analyses of indels fit remarkably well with differences in genetic diversity across gorilla taxa as recovered with nucleotide diversity measures. We also identified genes under selection and unique gene variants specific for each gorilla subspecies, encoding, among others, traits involved in immunity, diet, muscular development, hair morphology and behavior. The presence of this functional variation suggests that the subspecies may be locally adapted. In conclusion, using extensive genomic resources we provide a comprehensive overview of gorilla genomic diversity, including a so-far understudied Bwindi mountain gorilla population, identify putative genes involved in local adaptation, and detect population-specific gene flow across gorilla species.

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Novel Freshwater Cyanophages Provide New Insights into Evolutionary Relationships between Freshwater and Marine Cyanophages.

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