Fig. 4: Allelic gene activation during embryogenesis of hybrid animals.

a Expression heatmap of zygotic-only expressed genes from the 112-cell to late-neurula stage from both directional crosses. The genes were divided into four groups according to the expression preference. The purple, green, pink and orange groups contained C. robusta-, maternal-, C. savignyi- and paternal-dominant genes, respectively. b Gene expression preference quadrant for zygotic-only expressed genes from 112-cell to late-neurula stage. The quadrant is divided into four parts. X axis indicates the log₂ transformed expression ratio between genes from C. robusta and the allelic genes from C. savignyi in reverse cross embryos. Y axis indicates the log₂ transformed expression ratio between genes from C. robusta and the allelic genes from C. savignyi in forward cross embryos. Therefore, the first and third quadrants indicate genes with C. robusta- or C. savignyi-dominant expression, respectively, whereas the second and fourth quadrants indicate genes with maternal- or paternal-dominant expression, respectively. c Comparison of the distribution of a predicted cis-regulatory element and H3K27ac and Pol II occupancy by CUT&Tag at early neurula stage of titin gene from C. robusta and C. savignyi. The gene model and the predicted cis-regulatory element of titin were labeled. d Promoter activity test of titin. The promoters were cloned from C. robusta and C. savignyi, respectively. The swapped plasmids were cloned with exchange of motif regions. The plasmids were microinjected into C. savignyi embryos, and the GFP signals were observed from the early neurula to late tailbud stage. Scale bar: 50 μm. The experiment was independently performed at least three times. Source data are provided as a Source Data file.