Host Range and Coding Potential of Eukaryotic Giant Viruses

Abstract

Giant viruses are a group of eukaryotic double-stranded DNA viruses with large virion and genome size that challenged the traditional view of virus. Newly isolated strains and sequenced genomes in the last two decades have substantially advanced our knowledge of their host diversity, gene functions, and evolutionary history. Giant viruses are now known to infect hosts from all major supergroups in the eukaryotic tree of life, which predominantly comprises microbial organisms. The seven well-recognized viral clades (taxonomic families) have drastically different host range. Mimiviridae and Phycodnaviridae, both with notable intrafamilial genome variation and high abundance in environmental samples, have members that infect the most diverse eukaryotic lineages. Laboratory experiments and comparative genomics have shed light on the unprecedented functional potential of giant viruses, encoding proteins for genetic information flow, energy metabolism, synthesis of biomolecules, membrane transport, and sensing that allow for sophisticated control of intracellular conditions and cell-environment interactions. Evolutionary genomics can illuminate how current and past hosts shape viral gene repertoires, although it becomes more obscure with divergent sequences and deep phylogenies. Continued works to characterize giant viruses from marine and other environments will further contribute to our understanding of their host range, coding potential, and virus-host coevolution.

Discovery of Viral Myosin Genes With Complex Evolutionary History Within Plankton

“…However, this scenario cannot readily explain the monophyletic grouping of the virmyosins, as this scenario needs to additionally assume independent horizontal acquisitions of myosin genes by distantly related ancestral viruses from the same or closely related eukaryotes (e.g., ancestral SAR). Such acquisitions seem implausible because host changes are likely rampant events for Imitervirales given the wide host ranges of the known viruses in this group ( Sun et al, 2020 ). The third possibility is that a myosin gene transfer occurred once in a viral lineage of Imitervirales from its host.…”

Discovery of viral myosin genes with complex evolutionary history within plankton

“…However, this scenario cannot readily explain the monophyletic grouping of the virmyosins, as this scenario needs to additionally assume independent horizontal acquisitions of myosin genes by distantly related ancestral viruses from the same or closely related eukaryotes (e.g., ancestral Stramenopiles). Such acquisitions seem implausible because host changes are likely rampant events for Imitervirales given the wide host ranges of the known viruses in this group (Sun et al, 2020). The third possibility is that a myosin gene transfer occurred once in a viral lineage of Imitervirales from its host.…”

ViralRecall—A Flexible Command-Line Tool for the Detection of Giant Virus Signatures in ‘Omic Data

“…This group includes the largest viruses known, both in terms of physical dimensions and genome length [2]. Some members within the NCLDV group include those that infect metazoans and have been studied extensively, such as the Poxviridae, Iridoviridae, and Asfarviridae, while other families of NCLDVs, such as the Phycodnaviridae, Mimiviridae, Marseilleviridae, and Pithoviridae, have been discovered relatively recently and are known to infect protist lineages [3][4][5][6]. NCLDV genomes encode notably diverse functions that include many genes which are otherwise found only in cellular lineages, such as those involved in sphingolipid biosynthesis [7], amino acid metabolism [8], fermentation [9], glycolysis and the tricarboxylic acid (TCA) cycle [10], structuring of the eukaryotic cytoskeleton [11], and translation [12][13][14].…”