The subgenomes can show variable evolution considering initial and parental genome size after allotetraploidization. Asymmetric evolution of genomes has been observed in most animals and plants, where the dominance of one subgenome is relatively more effective by conducting reciprocal roles; normally one dominant genome is responsible for fundamental function, whereas the rest one is relaxed from selection for developing novel function. We have found that the symmetric subgenomes in goldfish in our previous study. This brings about a very intriguing question how symmetric subgenomes balance their function? Because it is harder to sustain the symmetric subgenomes due to competition of the subgenomes might exist. We found a valuable model in vertebrates, which has shared one allotetraploidization event, the Cyprinus shows asymmetrical evolution, while the Carassius genus and S. grahami exhibit a symmetrical evolution pattern similar to the Ca. auratus. How does this symmetry control the diversification stability and gene expression balance during rediploidization? The symmetric evolution of Ca. auratus may be closely related to the expression shifts of homologous gene pairs during embryonic development. Our previous epigenetic work indicated that 3D structure of chromatin alteration might be of importance during rediploidization. We found that shifts of homologous gene pairs are accompanied by changes in A/B compartment and modifications in TAD and loop structures. The results indicate that changes in 3D structure of chromatin play a key role in homologous gene pairs expression shifting during embryonic development in Ca. auratus. This study suggests that a balanced genome may play a subtle role in the diversity and genetic stability of species that share one allotetraploidization event.
 

Symmetric,allotetraploidization