Abstract
Anguillid herpesvirus 1 (AngHV-1) is a pathogen of eels and a member of the genus Cyprinivirus in the family Alloherpesviridae. We have compared the biological and genomic features of different AngHV-1 strains, focusing on their growth kinetics in vitro and genetic content, diversity, and recombination. Comparisons based on three core genes conserved among alloherpesviruses revealed that AngHV-1 exhibits a slower rate of change and less positive selection than other cypriniviruses. We propose that this may be linked to major differences in host species and corresponding epidemiological circumstances. Efforts to derive evolutionary rate estimates for cypriniviruses under various theoretical models were ultimately unrewarding. We highlight the potential value of future collaborative efforts towards generating short-term evolutionary rate estimates based on known sequence sampling dates. Finally, we revealed that there is significantly less genetic diversity in core gene sequences within cyprinivirus species clades compared to species in the family Herpesviridae. This suggests that cyprinivirus species may have undergone much more vigorous purifying selection post species clade divergence. We discuss whether this may be linked to biological and anthropogenic factors or to sampling bias, and we propose that the comparison of short-term evolutionary rates between species may provide further insights into these differences.
Highlights
The order Herpesvirales is composed of the three families Herpesviridae, Malacoherpesviridae and Alloherpesviridae [1,2,3,4]
Further analysis of three core genes revealed potential differences in evolutionary attributes between Anguillid herpesvirus 1 (AngHV-1) and other cypriniviruses, and the feasibility of using node calibration to derive absolute estimates of cyprinivirus evolutionary rates was explored. Further comparison of these three core gene sequences and that of a fourth core gene encoding uracil DNA glycosylase, indicated that species clades within the genus Cyprinivirus are less diverse than most well-characterized members of the family Herpesviridae
Both trees indicated that AngHV-1 has accumulated less change in these core genes since divergence from its most recent common ancestor (MRCA) with other cypriniviruses and that CyHV-2 has accumulated more changes
Summary
The order Herpesvirales is composed of the three families Herpesviridae, Malacoherpesviridae and Alloherpesviridae [1,2,3,4]. Prime examples of such genes include genes described as encoding the DNA polymerase catalytic subunit (hereafter called DNA polymerase), the helicase–primase helicase subunit (hereafter called helicase) and the terminase These represent some of the most conserved Alloherpesviridae core genes among members of the Cyprinivirus genus [9,10] and were the main focus of the present study. Further analysis of three core genes revealed potential differences in evolutionary attributes between AngHV-1 and other cypriniviruses, and the feasibility of using node calibration to derive absolute estimates of cyprinivirus evolutionary rates was explored Further comparison of these three core gene sequences and that of a fourth core gene encoding uracil DNA glycosylase (the latter being less well conserved between cypriniviruses), indicated that species clades within the genus Cyprinivirus are less diverse than most well-characterized members of the family Herpesviridae
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