SARS-CoV2 virus is believed to be originated from a closely related bat Coronavirus RaTG13 lineage and uses its key entry-point residues in S1 protein to attach with human ACE2 receptor. SARS-CoV2 could enter human from bat with its poorly developed entry-point residues much before its known appearance with slower mutation rate or recently with efficiently developed entry-point residues with higher mutation rate or through an intermediate host. Temporal analysis of SARS-CoV2 genome shows that its nucleotide substitution rate is as low as 27nt/year with an evolutionary rate of 9×10 −4 /site/year, which is well within the range of other RNA virus (10 −4 to 10 −6 /site/year). TMRCA of SARS-CoV2 from bat RaTG13 lineage appears to be in between 9 and 14 years. Evolution of a critical entry-point residue Y493Q needs two substitutions with an intermediate virus carrying Y493H (Y>H>Q) but has not been identified in known twenty-nine bat CoV virus. Genetic codon analysis indicates that SARS-CoV2 evolution during propagation in human disobeys neutral evolution as nonsynonymous mutations surpass synonymous mutations with the increase of ω (d n /d s ). Taken together, genetic data suggests that SARS-CoV2 is originated long time back before its appearance in human in 2019. Increase of ω signifies that SARs-CoV2 evolution is approaching towards diversifying selection from purifying selection predictably for its infection power to evade multiple human organs. Graphical abstract Image, graphical abstract .
【저자키워드】 COVID-19, Evolution, SARS-CoV2, Mutation, Divergent selection, 【초록키워드】 Infection, virus, RaTG13, Lineage, CoV, RNA virus, Critical, genetic data, Analysis, Evolutionary rate, Neutral, Image, Abstract, residue, Substitution, human ACE2 receptor, S1 protein, organs, nucleotide substitution, Host, synonymous, SARS-CoV2 genome, nonsynonymous mutation, appear, indicate, increase, evade, Temporal, 【제목키워드】 Invasion, favor, organ,