Molecular Evolution of RNA-Dependent RNA Polymerase Region in Norovirus Genogroup I

Norovirus is the leading viral agent of gastroenteritis in humans. RNA-dependent RNA polymerase (RdRp) is essential in the replication of norovirus RNA. Here, we present a comprehensive evolutionary analysis of the norovirus GI RdRp gene. Our results show that the norovirus GI RdRp gene can be divided into three groups, and that the most recent common ancestor was 1484. The overall evolutionary rate of GI RdRp is 1.821 x 10(-3) substitutions/site/year. Most of the amino acids of the GI RdRp gene were under negative selection, and only a few positively selected sites were recognized. Amino acid substitutions in the GI RdRp gene accumulated slowly over time. GI.P1, GI.P3 and GI.P6 owned the higher evolutionary rates. GI.P11 and GI.P13 had the faster accumulation rate of amino acid substitutions. GI.P2, GI.P3, GI.P4, GI.P6 and GI.P13 presented a strong linear evolution. These results reveal that the norovirus GI RdRp gene evolves conservatively, and that the molecular evolutionary characteristics of each P-genotype are diverse. Sequencing in RdRp and VP1 of norovirus should be advocated in the surveillance system to explore the effect of RdRp on norovirus activity.

Automated summary

Norovirus is the major viral cause of gastroenteritis in humans. The GI RdRp gene of norovirus can be categorized into three groups, with a common ancestor dating back to 1484. The overall evolutionary rate of GI RdRp is 1.821 x 10(-3) substitutions/site/year. Most amino acids in the GI RdRp gene are under negative selection, with only a few sites showing positive selection. Accumulation of amino acid substitutions in the GI RdRp gene is a slow process. Different P-genotypes exhibit diverse molecular evolutionary characteristics. Sequencing of RdRp and VP1 should be encouraged in the surveillance system to understand the role of RdRp in norovirus activity.