Fig. 3

Characteristics of MHCI and TAPBP genes in duck. Duck and chicken had five and two MHCI genes respectively. “*B4” and “*B21” represent different chicken MHC haplotypes. Lung and plasma tissues of control and infected ducks at 12 h, 24 h, and 48 h post inoculation were collected (n = 5). a Comparison of duck MHCIα proteins to chicken ones. Conserved residues interacting with CD8A or antigen peptide are highlighted in gray and green, respectively. There is a potential inference that two motifs may interact with the NK cell receptor [28], and these two motifs are shown in the orange rectangle. b Opening size of the peptide-binding pocket of duck MHCIα proteins and chicken BF2 proteins. c Electrostatic potential of duck MHCIα proteins. Area circled by white dotted lines is the peptide-binding pocket. d Lipophilic potential of duck MHCIα proteins. Pocket B is circled by white dotted lines. e Peptide recognition spectrum of duck MHCIα and chicken BF2 proteins. Short peptides (ranging from 8–10 aa) were randomly extracted from HA protein sequence and were docked into the binding groove of MHCIα proteins. Dots represented peptides could be bound by MHCIα. f Sequence alignment and domain of duck and chicken TAPBP protein. g Predicted interacting model between duck MHCI and TAPBP. h Expression heatmap of duck TAPBP gene. C1~C7 represent the numbers of 7 ducks. Detailed sample information is in Additional file 3: Data S6. i Transcripts of duck TAPBP gene