Effects and regulatory pathway of proopinmelanocortin on feeding habit domestication in mandarin fish

Proopiomelanocortin (POMC) is a hormone precursor, and has been reported to participate in domestication. However, its effects on feeding habit domestication in fish are poorly understood. Mandarin fish (Siniperca chuatsi) feeds solely on live prey fish since first-feeding. In the present study, the high expression of pomc in mandarin fish, both the pomc siRNA and MC4R inhibitor treatments increased the success rate of domestication from live prey fish to dead prey fish and food intake of dead prey fish, suggesting the role of pomc on the special feeding habit of live prey fish in mandarin fish. In addition, one c-fos binding site was identified in the region that from -1053 bp to -931 bp upstream of the transcription start site of pomc, and this region exhibited positive promoter activity. The mandarin fish brain cells treated with c-fos siRNA displayed suppressed pomc mRNA expression, indicating that c-fos positively regulated pomc expression. Furthermore, the mRNA expression of c-fos was higher in the mandarin fish which were more difficult to domesticate. The results of ChIP assay and inhibitor treatment confirmed that the activation of c-fos gene by histone H3K4me3 was catalyzed by Setd1b in mandarin fish. Three open peaks were found at the upstream regulatory region of setd1b by ATAC-seq, and the mRNA expression of setd1b was higher in the mandarin fish which were more difficult to domesticate. These results indicated that Setd1b could methylate histone H3K4 to activate the c-fos transcription, maintaining the high expression of pomc, which might contribute to the special feeding habit of mandarin fish.

Whole-genome resequencing and bisulfite sequencing provide new insights into the feeding habit domestication in mandarin fish (Siniperca chuatsi)

Mandarin fish (Siniperca chuatsi) is one of the most economically important fish in China. However, it has the peculiar feeding habit that it feeds solely on live prey fish since first-feeding, while refuses dead prey fish or artificial diets. After the specific training procedure, partial individuals could accept dead prey fish and artificial diets. The genetic basis of individual difference in artificial diet feeding habit is still unknown. In the present study, the resequencing was performed between 10 individuals which could be domesticated to accept artificial diets and 10 individuals which could not. Through the selective sweep analysis based on heterozygosity (Hp) and population differentiation coefficient (Fst), 57 candidate windows were identified as the putative selected regions for feeding habit domestication of mandarin fish, involved in 149 genes. These genes were related to memory, vision and olfaction function, which could be potential targets of molecular marker assistant breeding of artificial diet feeding trait. Beside of the DNA sequence, we also explored the potential role of DNA methylation in feeding habit domestication in mandarin fish. Whole-genome bisulfite sequencing was performed between the individuals which could be domesticated to accept artificial diets and those could not. 5,976 differentially methylated regions were identified, referring to 3,522 genes, such as the genes involved in cAMP signaling pathway. The DNA methylation changes of these genes might contribute to the adaption of artificial diets in mandarin fish. In conclusion, the putative selected regions and the differentially methylated regions were identified in the whole genome, providing new insights into the feeding habit domestication from live prey fish to artificial diets in mandarin fish. And the involved genes were identified as the candidate genes for molecular breeding of artificial diet utilization in mandarin fish.