Fig. 3

Structure of bat PSGs. a The exon structure of a typical bat PSG mRNA, composed of a leader sequence (black), an IgV-like domain exon (blue) and an IgC-like domain exon (black), is shown. 5′-UTR and 3′-UTR are shown in green. The start codon, the stop codon and the polyadenylation signals are shown in red. The stop codon in Mlu_PSG1 is located at the end of the A domain exon. In other bat PSGs the stop codon is also in the A domain exons at varying positions (not shown). b Nucleotide sequences of the IgC-like domains of one representative PSG each from M. lucifugus and P. parnellii were aligned with the sequences of IgC-like domains of CEACAM1 from M. lucifugus (A1, B and A2). The relationship of the sequences is depicted as a rooted dendrogram which was calculated using the MEGA5 software. The statistical support for each node is expressed as bootstrap values. The bar below the phylogenetic tree shows the scale for the number of substitutions per site. c Comparison of the domain organization of microbat PSGs with PSGs in primates, rodents and horse. IgV-like domains are depicted in red and IgC-like domains in blue