The Genetic Signatures of Domestication in Pigs and Chickens

Understanding the Evolutionary Changes Shaped by Human Intervention

The domestication of wild animals into livestock has been a cornerstone of human civilization, providing essential resources such as food, clothing, and labor. A recent study¹ by Hiroshima University has delved into the genetic changes that have occurred in pigs and chickens as a result of this domestication process, revealing how their genes have adapted to express different traits compared to their wild ancestors, the wild boars, and red jungle-fowl.

The Path to Domestication: From Wild Ancestors to Modern Livestock

The journey from wild boars and red jungle-fowl to domesticated pigs and chickens involves significant genetic alterations. These changes have led to physical and physiological traits that are beneficial for agricultural purposes, such as faster growth rates, improved meat quality, and enhanced viral resistance. However, these modifications have also resulted in weaker bones and other health issues.

Professor Hidemasa Bono, from Hiroshima University’s Laboratory of Genome Informatics, explains:

“Through domestication, these animals have been selectively bred for specific traits useful to humans. This process has significantly altered their behavior, morphology, and physiological functions. Understanding these changes is crucial for addressing health issues in domesticated animals and improving their reproductive capacity.”

Genetic Analysis: Uncovering the Secrets of Domestication

The research team conducted a comparative study using data from publicly available databases, examining gene expression in pairs of pigs and wild boars, as well as pairs of chickens and red jungle-fowl. They focused on 240 genes in pigs and 206 in chickens, discovering that 10 genes were up-regulated in domesticated animals, meaning they were expressed more compared to their wild ancestors. Conversely, seven genes were up-regulated in wild boars and red jungle-fowl.

A total of 46 pairs of pig and wild boar data and 59 pairs of chicken and red junglefowl data were obtained from public databases. By integrating and analyzing these data, comparative analyses of pig-wild boar and chicken-red jungle-fowl were conducted. Furthermore, genes with common expression changes between domesticated animals (pigs and chickens) and their wild ancestors (wild boars and red junglefowl) were identified. (Courtesy of Motoki Uno/Hiroshima University)

Motoki Uno, a graduate student in the Laboratory of Genome Informatics, highlights the findings:

“Domesticated animals exhibited higher expression of genes related to viral resistance and bone weakness, whereas their wild ancestors showed higher expression of genes associated with stress response and energy metabolism.”

The Impact of Environment on Gene Expression

The study reveals that the different living conditions of domesticated animals and their wild counterparts have significantly influenced gene expression. Domesticated animals, often kept in high-density, confined spaces, are more susceptible to viral infections, necessitating a stronger immune response. In contrast, wild boars and red jungle-fowl face more natural stressors, such as predators and food scarcity, leading to higher expression of genes related to stress response and energy metabolism. Uno says,

“Our analysis showed that genes commonly up-regulated in pigs and chickens are involved in immune response, olfactory learning, epigenetic regulation, cell division, and the extracellular matrix. On the other hand, genes up-regulated in wild boar and red jungle-fowl are related to stress response, cell proliferation, cardiovascular function, neural regulation, and energy metabolism.”

Future Implications for Livestock Breeding

These insights provide a valuable understanding of the genetic basis of domestication and identify potential candidate genes for improving livestock breeding. The study underscores the importance of developing sustainable breeding practices that balance productivity with animal health and welfare. Bono states,

“Moving forward, we aim to contribute to sustainable breeding through the improvement of analytical methods and the integration of various biological data.”

This research, funded by the Center of Innovation for Bio-Digital Transformation and the Japan Science and Technology Agency, sets the stage for future advancements in the field of genomics and animal breeding.

By continuing to explore the genetic foundations of domestication, scientists hope to enhance the health and productivity of livestock, ultimately benefiting both animals and humans. The study from Hiroshima University highlights the intricate genetic changes that domestication has brought about in pigs and chickens. By understanding these changes, researchers can better address the health issues that have arisen from selective breeding and pave the way for more sustainable and productive livestock farming practices.

1. Uno, M., & Bono, H. (2024). Transcriptional signatures of domestication revealed through meta-analysis of pig, chicken, wild boar, and red junglefowl gene expression data. Animals: An Open Access Journal from MDPI, 14(13), 1998. https://doi.org/10.3390/ani14131998