Classical Genome Organization of IBV-Ark DPI. The genome of Ark DPI is 27,620 nt long, excluding poly (A) tract. Middle: ten genes and its ORFs. Ribosomal frameshift and position of transcriptional regulatory sequences (TRS) of each gene is indicated. Top: putative domains of ORF1a/1b polyprotein: nsp-non-structural protein, Ac-acidic domain, X-unknown domain X, PL1- papain like proteinase1, PL2-papain like proteinase 2; Y-unknown domain Y; HD-hydrophobic domain, 3CL-3C-like proteinase, G-Growth factor like protein, RdRp-RNA dependent RNA polymerase, Hel-helicase, ExoN-exoribonuclease, Ne-nidoviral uridylate-specific endoribonuclease, MT- 2'-O-ribose methyltransferase. Bottom: details of spike protein; SP-signal peptide, RRSRR/S- spike protein cleavage site between 544 and 545aa, TM-transmembrane domain of spike protein.