Figure 9

Coding potential statistics for bat coronavirus 1A/1B/HKU8 ORF3 and the overlapping ORFX. (1) Map of the ORF3 region of BtCoV 1A [GenBank: EU420138], showing the proposed new coding sequence, ORFX, overlapping ORF3 in the +1 reading frame. (2-5) Coding potential statistics based on an alignment of BtCoV 1A, 1B and HKU8 (see Figure 10 for accession numbers). (2-4) Positions of stop codons in each of the three forward reading frames. Note the conserved absence of stop codons in the +1 frame within the ORFX region. (5) MLOGD statistics for ORF3 relative to a non-coding null model. (6) MLOGD statistics for ORFX (see Figure 3 for details). The predominantly positive scores indicate that ORFX is likely to be a coding sequence, but is subject to significantly weaker purifying selection than ORF3. The negative scores at the 3' end of ORFX indicate that the C-terminal region of the putative product is not subject to strong functional constraints.