Abstract
BackgroundHeterosis is an important biological phenomenon that has been extensively utilized in agricultural breeding. However, negative heterosis is also pervasively observed in nature, which can cause unfavorable impacts on production performance. Compared with systematic studies of positive heterosis, the phenomenon of negative heterosis has been largely ignored in genetic studies and breeding programs, and the genetic mechanism of this phenomenon has not been thoroughly elucidated to date. Here, we used chickens, the most common agricultural animals worldwide, to determine the genetic and molecular mechanisms of negative heterosis.ResultsWe performed reciprocal crossing experiments with two distinct chicken lines and found that the body weight presented widely negative heterosis in the early growth of chickens. Negative heterosis of carcass traits was more common than positive heterosis, especially breast muscle mass, which was over − 40% in reciprocal progenies. Genome-wide gene expression pattern analyses of breast muscle tissues revealed that nonadditivity, including dominance and overdominace, was the major gene inheritance pattern. Nonadditive genes, including a substantial number of genes encoding ATPase and NADH dehydrogenase, accounted for more than 68% of differentially expressed genes in reciprocal crosses (4257 of 5587 and 3617 of 5243, respectively). Moreover, nonadditive genes were significantly associated with the biological process of oxidative phosphorylation, which is the major metabolic pathway for energy release and animal growth and development. The detection of ATP content and ATPase activity for purebred and crossbred progenies further confirmed that chickens with lower muscle yield had lower ATP concentrations but higher hydrolysis activity, which supported the important role of oxidative phosphorylation in negative heterosis for growth traits in chickens.ConclusionsThese findings revealed that nonadditive genes and their related oxidative phosphorylation were the major genetic and molecular factors in the negative heterosis of growth in chickens, which would be beneficial to future breeding strategies.
Highlights
Heterosis is an important biological phenomenon that has been extensively utilized in agricultural breeding
As shown in the dynamic growth of parental lines and reciprocal crosses, the body weights of females and males in CR and RC from 2 to 8 weeks of age were lower than the average of CC and RR (Fig. 1a, b and Table S1), reciprocal crosses exhibited slightly positive heterosis for the length of shank and sternum at 6 and 8 weeks of age (Table S5)
We characterized the transcriptome profiles of breast muscle in reciprocal crosses and the parental lines to reveal the potential mechanisms of negative heterosis for growth traits in chickens
Summary
Heterosis is an important biological phenomenon that has been extensively utilized in agricultural breeding. Numerous studies have attempted to explain the genetic mechanism of heterosis, and three classic quantitative genetic hypotheses have been proposed: dominance [3, 4], overdominance [1, 5], and epistasis [6, 7]. These three models were mainly theoretical and could not provide a full explanation for the molecular basis and physiological causes of heterosis [8, 9]. Hedgecock et al [14] conducted transcriptomic analysis in Crassostrea gigas and found that nonadditive genes and their related protein metabolism played important roles in growth heterosis
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