Acipenser iridovirus-European encodes a replication factor C (RFC) sub-unit

Area of Science:

• Virology
• Genomics
• Molecular Biology

Background:

• The Acipenser iridovirus-European (AcIV-E) remains poorly characterized, with its complete genome and classification yet to be determined.
• Understanding the genetic makeup of AcIV-E is crucial for its classification within the Iridoviridae family and for comprehending its impact on sturgeon populations.

Purpose of the Study:

• To obtain the first full-length Major capsid protein (MCP) gene sequence for AcIV-E.
• To identify and characterize additional open reading frames (ORFs) adjacent to the MCP gene.
• To investigate the genetic diversity and co-infection patterns of AcIV-E lineages in European sturgeon.

Main Methods:

• Sequencing of the full-length Major capsid protein (MCP) gene and adjacent ORFs in AcIV-E.
• BLAST searches against public databases to identify homologous genes and proteins.
• Phylogenetic analysis of the replication factor C (RFC) gene sequences from various AcIV-E isolates.
• Comparative genomics to infer genome size and replication mechanisms.

Main Results:

• The first full-length Major capsid protein (MCP) gene sequence for AcIV-E was successfully obtained.
• Two additional ORFs were identified: ORF α with no database matches and ORF β identified as a replication factor C (RFC) subunit.
• The presence of an RFC gene in AcIV-E suggests a larger genome size and a replication mechanism involving clamp loaders.
• Sequence analysis of the RFC gene revealed two distinct clusters, confirming the co-circulation of at least two AcIV-E lineages, often co-infecting European sturgeon.

Conclusions:

• The identification of an RFC gene in AcIV-E provides significant insights into its potential genome size and replication strategy.
• Genetic evidence strongly supports the existence and co-circulation of at least two distinct AcIV-E lineages.
• These findings highlight the complexity of AcIV-E infections in cultured European sturgeon and the need for further genomic investigation.