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Type Species |
(EsV-1) |
Ectocarpus siliculosus virus 1 (EsV-1) viruses infect the free-swimming, zoospore stage of filamentous brown algal hosts. The virus genome presumably becomes integrated into the host genome and is inherited in a Mendelian manner. Virus particles are only formed in prospective gametangia or sporangia cells of the host. The viral genomes are circular dsDNAs.
List of Species Demarcation Criteria in the Genus
Six species of viruses are delineated based in part on host specificity. Field isolates of at least six genera of the Phaeophycae contain 120 to 150 nm in diameter polyhedral virus-like particles. The particles contain dsDNA genomes that vary in size from 150 to 350 kb, although major capsid protein (CP) gene and DNA polymerase sequence data indicate that they are closely related. Virus expression is variable; particles are rarely observed in vegetative cells but are common in unilocular sporangia (FsV) or both unilocular and plurilocular sporangia (EsV). Some of the viruses have a narrow host range (FsV) whereas others such as Feldmannia irregularis virus (FiV) and EsV infect members of more than one genus.
Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names and assigned abbreviations ( ) are:
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Ectocarpus fasciculatus virus a |
(EfV-a) |
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Ectocarpus siliculosus virus 1 |
(EsV-1) |
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Ectocarpus siliculosus virus a |
(EsV-a) |
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Feldmannia irregularis virus a |
(FiV-a) |
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Feldmannia species virus |
(FsV) |
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Feldmannia species virus a |
(FsV-a) |
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Hincksia hinckiae virus a |
(HhV-a) |
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Myriotrichia clavaeformis virus a |
(McV-a) |
Tentative Species in the Genus
None reported.
List of Unassigned Viruses in the Family
None reported.
Phylogenetic Relationships within the Family
Analysis of the DNA polymerase gene from selected members of the family Phycodnaviridae indicate that the viruses are more closely related to each other than to other dsDNA viruses and they form a distinct phyletic group suggesting that they share a common ancestor (Fig. 2). However, the viruses fall into four clades, which correlete with their hosts. For example, the nucleotide sequence from the chlorovirus PBCV-1 is 77% identical to both Paramecium bursaria Chlorella virus NY2A (PBCV-NY2A) and Paramecium bursaria Chlorella virus A1 (PBCV-A1), while CVA-1 and NY-2A are 64% identical. Among prasinoviruses, the proportion of identical nucleotides for all pairwise combinations ranged from 78 to 99%. The two prymnesioviruses Chrysochromulina brevifilum virus PW1 (CbV-PW1) and Chrysochromulina brevifilum virus PW3 (CbV-PW3) are 98% identical. Overall, sequence identities among the DNA polymerase gene fragments of all prasinoviruses and prymnesioviruses, and three chloroviruses ranged from 49 to 99%. Furthermore, the members of the family Phycodnaviridae share higher sequence similarity to each other than to members of other families.
Many large polyhedral virus-like particles have been observed in electron micrographs of eukaryotic algae. However, for the most part these particles have not been characterized. Particles isolated from three of these algae are reported to contain large dsDNA genomes of unknown structure.
Chloro: from Greek chloro, meaning “green”.
dna: sigla for deoxyribonucleic acid.
Phaeo: from Greek phaeo, meaning “brown”.
Phyco: from Greek phycos, meaning “plant”.
Prasinov: from Latin prasino, meaning “green”.
Prymnesio: from Greek prymne, meaning “stern of a ship”.
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