Fig. 7: Relative allelic expression (RAE) and fractional occupancies of alleles in hybrids and polyploids with respect to parental expression divergence.

A RAE in hybrids and polyploids under the limited cross-regulation (\(\rho=2\)). X-axis demonstrates the expression differentiation between parental species in terms of their fractional occupancies \({\log }_{2}({f}_{{{\rm{A}}}}/{f}_{{{\rm{B}}}})\), \(y\)-axis indicates the relative allelic ratios of orthologous (parental) alleles A_hyb and B_hyb in a hybrid, normalized by their genomic dosage \({\log }_{2}({f}_{{{\rm{H}}}}^{{{\rm{A}}}}/{f}_{{{\rm{H}}}}^{{{\rm{B}}}})\) (note that A-derived binding sites have twice higher absolute numbers in AA species than in AB hybrid and identical to AAB triploid). Coefficients a of regression slopes are estimated upon the assumption of a linear fit of each curve for diploid AB (red), triploid AAB (black) and triploid ABB (blue). B Comparison of fractional occupancies of alleles in hybrids (\({f}_{{{\rm{H}}}}^{{{\rm{A}}}}\) and \({f}_{{{\rm{H}}}}^{{{\rm{B}}}}\), respectively) relative to occupancies of their homologous alleles in parents (\({f}_{{{\rm{A}}}}\) and \({f}_{{{\rm{B}}}}\), respectively). X-axis shows the \({\log }_{2}({{f}_{{{\rm{H}}}}^{{{\rm{A}}}}/f}_{{{\rm{A}}}})\) ratio of A_hyb allele’s occupancy in hybrid relative to that in parental species A, \(y\)-axis shows the \({\log }_{2}({{f}_{{{\rm{H}}}}^{{{\rm{B}}}}/f}_{{{\rm{B}}}})\) ratio of B_hyb allele’s occupancy in hybrid relative to that in parental species B. Line colours and styles are identical to the panel A. Note: Square and diamond symbols along the lines provide the link between panels A and B by showing two reference values of \({\log }_{2}({{f}}_{{{\rm{A}}}}/{{f}}_{{{\rm{B}}}})\) expression divergence between parental species; square: \({\log }_{2}({{f}}_{{{\rm{A}}}}/{{f}}_{{{\rm{B}}}})=-1\) and diamond: \({\log }_{2}({{f}}_{{{\rm{A}}}}/{{f}}_{{{\rm{B}}}})=1\).