Title: Codon pattern reveals SARS-CoV-2 to be a monomorphic strain that emerged through recombination of replicase and envelope alleles of bat and pangolin origin
Abstract: Viruses are dependent on the host tRNA pool, and an optimum codon usage pattern (CUP) is a driving force in its evolution. Systematic analysis of CUP of replicase (rdrp), spike, envelope (E), membrane glycoprotein (M), and nucleocapsid (N) encoding genes of SARS-CoV-2 from reported diverse lineages to suggest one-time host jump of a SARS-CoV-2 isolate into the human host. In contrast to human isolates, a high degree of variation in CUP of these genes suggests that bats, pangolins, and dogs are natural reservoirs of diverse strains. At the same time, our analysis suggests that dogs are not a source of SARS-CoV-2. Interestingly, CUP of rdrp displays conservation with two bat SARS isolates RaTG13 and RmYN02. CUP of the SARS-CoV-2 E gene is also conserved with bat and pangolin isolates with variations for a few amino acids. This suggests role allele replacement in these two genes involving SARS strains of least two hosts. At the same time, a relatively conserved CUP pattern in replicase and envelope across hosts suggests them it to be an ideal target in antiviral development for SARS-CoV-2.