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Evolutionary analysis of influenza C virus M genes
1Department of Bacteriology, Yamagata University School of Medicine, Japan.
Abstract:
The previous study of the 25 hemagglutinin-esterase (HE) glycoprotein genes of influenza C viruses identified four discrete lineages represented by C/Yamagata/26/81, C/Aichi/1/81, C/Aomori/74 and C/Mississippi/80, respectively. Here we compared the M gene sequence among the 24 viruses isolated between 1964 and 1991. A phylogenetic analysis showed that these genes have evolved into three distinct lineages. Lineage I included most of viruses with the HE genes of C/Yamagata/26/81-related lineage. The predominant members of lineage II were viruses having the HE genes of either C/Aichi/1/81- or C/Mississippi/80-related lineage. Lineage III contained only C/Aomori/74. Phylogenetic positions of several strains (C/Yamagata/64, C/Kanagawa/1/76, C/Miyagi/77 and C/Nara/1/85) were different between the M and HE gene trees, suggesting that they are reassortants. Furthermore, phylogenetic relationships between C/Mississippi/80-like and C/Aichi/1/81-like viruses were much closer for the M gene than the HE gene, raising the possibility that these two virus groups are genetically related by a reassortment event. Nucleotide changes in the M genes occurred at about 7% positions with a uniform distribution throughout the molecules. However, the predicted amino acid sequence of the matrix protein (M1) was conserved almost completely among the isolates analyzed. The amino acid sequence of the second protein (CM2) encoded by M gene was also highly conserved, but was more divergent than the M1 protein sequence, suggesting that the two M gene products are evolving differently in response to selective pressures or structural and functional constraints.
Insights
Influenza C virus M genes evolved into three lineages, distinct from HE gene lineages. Some viruses show reassortment, suggesting genetic exchange between influenza C virus groups.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Previous studies identified four hemagglutinin-esterase (HE) glycoprotein gene lineages in influenza C viruses.
- Influenza C viruses possess segmented genomes, allowing for genetic reassortment.
Purpose of the Study:
- To compare the M gene sequence evolution of influenza C viruses.
- To investigate potential reassortment events between different influenza C virus lineages.
Main Methods:
- Phylogenetic analysis of M gene sequences from 24 influenza C virus isolates (1964-1991).
- Comparison of M gene phylogeny with previously established HE gene phylogenies.
- Analysis of nucleotide and amino acid sequence conservation in M gene products (M1 and CM2 proteins).
Main Results:
- M gene sequences clustered into three distinct phylogenetic lineages, differing from the four HE gene lineages.
- Several influenza C virus strains exhibited different phylogenetic positions based on M and HE genes, indicating reassortment.
- Closer M gene relationships between C/Mississippi/80-like and C/Aichi/1/81-like viruses suggest a reassortment event.
- While nucleotide sequences showed variation, the M1 and CM2 protein sequences were highly conserved, with CM2 being more divergent.
Conclusions:
- The M gene has evolved into distinct lineages within influenza C viruses.
- Reassortment events likely contribute to the genetic diversity of influenza C viruses.
- Differential evolutionary pressures may act on the M1 and CM2 proteins encoded by the M gene.