Our Dunphy research team has made progress in the study of viral diversity in the polar regions

Recently, the State Key Laboratory of Virology and the National Virus Resource Database/Wuhan Institute of Virology, Chinese Academy of Sciences/School of Life Sciences, Wuhan University/College of Life Sciences, Xinjiang University/ A joint team from the Department of Biochemistry at Boston University School of Medicine made important progress
in retrospective studies of metagenomic data from Antarctic animal faeces and Arctic permafrost from 2012 to 2014.
Diverse viromes in polar regions: A retrospective study of metagenomic data from Antarctic animal feces and Arctic frozen soil in 2012–2014" was published online in
Virologica Sinica.

The Antarctic and Arctic are the coldest places on Earth, and the polar environment contains a variety of microorganisms, including viruses, which are important components of
the polar ecosystem.
However, animal and environmental samples from the polar regions are difficult to obtain, resulting in limited understanding of the virus in the polar regions
.
To better understand polar viruses, retrospective analysis was performed using metagenomic sequencing data from Antarctic animal faeces and Arctic permafrost collected in 2012-2014 (Figure 1).

Figure 1 Schematic diagram of the North and South Poles sample collection points

In antarctic animal feces, the virus sequences identified involved 14 DNA viridae (dsDNA viruses: Autographiviridae, Myoviridae、Podoviridae、Siphoviridae、Herelleviridae、 Lavidaviridae, Mimiviridae, Phycodnaviridae and Totiviridae; ssDNA：Anelloviridae、Circoviridae、Microviridae、 Inoviridae and Parvoviridae) and 9 RNA viridae (dsRNA Viruses: Birnaviridae, Cystoviridae and Partitiviridae; ssRNA viruses: Dicistroviridae, Marnaviridae, Nodaviridae, Picornaviridae, Tombusviridae and Metaviridae
。 In addition, unclassified virus-related sequences were sent (Figure 2).

Figure 2 Viral communities and sequence characteristics of different families of viruses in animal feces in Antarctica

Virus-related sequences have been found in Arctic permafrost, including 14 DNA viridae (dsDNA viruses: Alloherpesviridae, Demerecviridae、Iridoviridae、Mimiviridae、Myoviridae、 Phycodnaviridae、Podoviridae、Siphoviridae、Caulimoviridae； ssDNA viruses: Circoviridae, Parvoviridae, Genomoviridae, Inoviridae, Microviridae) and 2 RNA viridae (dsRNA viruses: Partitiviridae； ssRNA virus: Metaviridae), and with Caudovirales, Nucleocytoviricota, and Caudovirales Ribviria related viruses but not clearly classified family taxonomic properties and many unclassified virus sequences (Figure 3).

Figure 3 Sequence characteristics of viral communities and phages of different families in Arctic soils

Although Antarctica and the Arctic are geographically isolated from each other, viral sequences may also share evolutionary relevance
with known viruses of different origins around the world.
Comparing and analyzing virus-related sequences with virus sequences in IMG/VR databases, it was found that the virus sequences in Antarctic animal feces samples were mainly related to viruses in aquatic environments (32.
25%), followed by humans (11.
44%), viruses in terrestrial environments ( 11%), plants (8.
38%), etc
.
The similarity of virus sequences in Arctic soil to known viruses of different habitat sources on Earth is roughly similar to that of Antarctica (Figure 4A), suggesting that although the Antarctic and Arctic are geographically distant and isolated, polar viruses have genetic homology with viruses in other habitats around the world
.
Predictions of viral protein function found that viral protein homologs clustered together to form 27 functional clusters with more than 3 nodes, further indicating a functional association between viral taxa in Antarctic fecal samples and Arctic soil samples (Figure 4B).

。

Figure 4 Genetic correlation and functional homology analysis
of viral communities in polar regions.

In this study, a phylogenetic analysis of new viral sequences related to the Microviridae, Parvoviridae and Larvidaviridae families was performed.
Whole genome sequences
of two CRESS DNA viruses closely related to the Circoviridae family were also obtained.

Figure 5 Phylogenetic analysis of viral sequences found in Antarctic animal feces and Arctic soils

These results reveal the high diversity, complexity and novelty of polar virus communities, and further discuss the changes in Arctic and Arctic virus taxa in Arctic soil, Arctic freshwater and Antarctic soil and their genetic similarity and functional correlation
through comparative analysis of published data.
These findings improve our understanding of polar viruses and demonstrate the importance of follow-up in-depth investigations of animal and environmental samples from the Antarctic and Arctic, revealing the important role
of these viruses in global viral populations.

Wang Jun, senior engineer of the National Virus Resource Database, Wuhan Institute of Virology, Chinese Academy of Sciences, and Xiao Jian, Ph.
D.
, Wuhan Institute of Virology, Chinese Academy of Sciences, are the co-first authors of the paper.
Deng Fei, researcher of Wuhan Institute of Virology, Chinese Academy of Sciences/Shen Shu, young researcher of Wuhan Institute of Virology, Chinese Academy of Sciences/Professor Peng Fang, School of Life Sciences, Wuhan University, are the co-corresponding authors
of this paper.
The research was supported by the Key Deployment Program of the Chinese Academy of Sciences (KJZD-SW-L11), the International Partnership Program of the International Cooperation Bureau of the Chinese Academy of Sciences (153B42KYSB20200013), and the Chinese Academy of Sciences (Category B).
XDB42000000), National Natural Science Foundation of China (Grant No.
: 31900154), China Polar Science Strategic Research Foundation (IC201706) and other funds
.

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