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Abstract
Heterosis, a phenomenon characterized by the superior performance of hybrid individuals relative to their parents, has been widely utilized in livestock and crop breeding, while the underlying genetic basis remains elusive in chickens. Here, we performed a reciprocal crossing experiment with broiler and layer chickens and conducted RNA sequencing on liver tissues for reciprocal crosses and their parental lines to identify inheritance patterns of gene expression. Our results showed that heterosis of the abdominal fat percentage was 69.28%–154.71% in reciprocal crosses. Over-dominant genes of reciprocal crosses were significantly enriched in three biological pathways, namely, butanoate metabolism, the synthesis and degradation of ketone bodies, and valine, leucine, and isoleucine degradation. Among these shared over-dominant genes, we found that a lipid-related gene, HMGCL, was enriched in these pathways. Furthermore, we validated this gene as over-dominant using qRT-PCR. Although no shared significant pathway was detected in the high-parent dominant genes of reciprocal crosses, high-parent dominant gene expression was the major gene inheritance pattern in reciprocal crosses and we could not exclude the effect of high-parent dominant genes. These findings suggest that non-additive genes play important roles in the heterosis of important traits in chickens and have important implications regarding our understanding of heterosis.
Highlights
Heterosis or, more narrowly, hybrid vigor refers to the phenomenon in which progenies exhibit greater biomass, speed of development, or fertility than their parents [1]
Given that the pathways of butanoate metabolism, synthesis and degradation of ketone bodies, and valine, leucine, and isoleucine degradation were significantly enriched in over-dominant genes for both the CR and RC groups, we focused on genes exhibiting over-dominance in the CR and RC
Genome-wide transcript profiles of livers were applied to gain a global view of gene expression in the reciprocal crosses and parental lines to reveal the genetic basis of heterosis for abdominal fat percentage (AFP) in chickens
Summary
More narrowly, hybrid vigor refers to the phenomenon in which progenies exhibit greater biomass, speed of development, or fertility than their parents [1]. Plant and animal breeders exploit heterosis by mating two different pure-bred lines with certain desirable traits, and have driven unprecedented improvements in performance or viability in crops and livestock [2,3]. Heterosis does not always imply superiority, as it depends on the trait’s biological significance and production preference. Several studies demonstrated that maize and wheat exhibiting heterosis for height had weaker lodging resistance than shorter individuals [4,5]. It is well understood that a greater cocoon shell thickness affects the hatching of silkworms [6,7].
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