TY - JOUR
T1 - Functional Genomic Analyses Reveal an Open Pan-genome for the Chloroviruses and a Potential for Genetic Innovation in New Isolates
AU - Rodrigues, Rodrigo A.L.
AU - Queiroz, Victória F.
AU - Ghosh, Jayadri
AU - Dunigan, David D.
AU - van Etten, James L.
N1 - Funding Information:
This work was funded in part by the National Science Foundation under grant no. 1736030 (J.L.V.E.), the University of Nebraska—Lincoln Agricultural Research Division and Office of Research and Economic Development (D.D.D.), and the University of Nebraska Collaborative Initiative Seed Grant Program (D.D.D.). R.A.L.R. and V.F.Q. were CNPq and/or CAPES stipend recipients of the Post-graduation Program in Microbiology/UFMG.
Funding Information:
This work was funded in part by the National Science Foundation under grant no. 1736030 (J.L.V.E.), the University of Nebraska?Lincoln Agricultural Research Division and Office of Research and Economic Development (D.D.D.), and the University of Nebraska Collaborative Initiative Seed Grant Program (D.D.D.). R.A.L.R. and V.F.Q. were CNPq and/or CAPES stipend recipients of the Post-graduation Program in Microbiology/UFMG.
Publisher Copyright:
Copyright © 2022 American Society for Microbiology. All Rights Reserved.
PY - 2022/1
Y1 - 2022/1
N2 - Chloroviruses (family Phycodnaviridae) are large double-stranded DNA (dsDNA) viruses that infect unicellular green algae present in inland waters. These viruses have been isolated using three main chlorella-like green algal host cells, traditionally called NC64A, SAG, and Pbi, revealing extensive genetic diversity. In this study, we performed a functional genomic analysis on 36 chloroviruses that infected the three different hosts. Phylogenetic reconstruction based on the DNA polymerase B family gene clustered the chloroviruses into three distinct clades. The viral pan-genome consists of 1,345 clusters of orthologous groups of genes (COGs), with 126 COGs conserved in all viruses. Totals of 368, 268, and 265 COGs are found exclusively in viruses that infect NC64A, SAG, and Pbi algal hosts, respectively. Two-thirds of the COGs have no known function, constituting the “dark pan-genome” of chloroviruses, and further studies focusing on these genes may identify important novelties. The proportions of functionally characterized COGs composing the pan-genome and the core-genome are similar, but those related to transcription and RNA processing, protein metabolism, and virion morphogenesis are at least 4-fold more represented in the core genome. Bipartite network construction evidencing the COG sharing among host-specific viruses identified 270 COGs shared by at least one virus from each of the different host groups. Finally, our results reveal an open pan-genome for chloroviruses and a well-established core genome, indicating that the isolation of new chloroviruses can be a valuable source of genetic discovery.
AB - Chloroviruses (family Phycodnaviridae) are large double-stranded DNA (dsDNA) viruses that infect unicellular green algae present in inland waters. These viruses have been isolated using three main chlorella-like green algal host cells, traditionally called NC64A, SAG, and Pbi, revealing extensive genetic diversity. In this study, we performed a functional genomic analysis on 36 chloroviruses that infected the three different hosts. Phylogenetic reconstruction based on the DNA polymerase B family gene clustered the chloroviruses into three distinct clades. The viral pan-genome consists of 1,345 clusters of orthologous groups of genes (COGs), with 126 COGs conserved in all viruses. Totals of 368, 268, and 265 COGs are found exclusively in viruses that infect NC64A, SAG, and Pbi algal hosts, respectively. Two-thirds of the COGs have no known function, constituting the “dark pan-genome” of chloroviruses, and further studies focusing on these genes may identify important novelties. The proportions of functionally characterized COGs composing the pan-genome and the core-genome are similar, but those related to transcription and RNA processing, protein metabolism, and virion morphogenesis are at least 4-fold more represented in the core genome. Bipartite network construction evidencing the COG sharing among host-specific viruses identified 270 COGs shared by at least one virus from each of the different host groups. Finally, our results reveal an open pan-genome for chloroviruses and a well-established core genome, indicating that the isolation of new chloroviruses can be a valuable source of genetic discovery.
KW - Chloroviruses
KW - Evolution
KW - Genomics
KW - Pan-genome
KW - Phycodnaviridae
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UR - http://www.scopus.com/inward/citedby.url?scp=85123871426&partnerID=8YFLogxK
U2 - 10.1128/JVI.01367-21
DO - 10.1128/JVI.01367-21
M3 - Article
C2 - 34669449
AN - SCOPUS:85123871426
SN - 0022-538X
VL - 96
JO - Journal of virology
JF - Journal of virology
IS - 2
M1 - e01367-21
ER -