Oink oink! Scientists are happy to report that they've finished mapping the pig genome, a feat that could help the agricultural industry breed better bacon and provide crucial insights into biomedicine and pig evolution.
A team of international researchers sequenced the genome of the domesticated pig, Sus scrofa domesticus, and compared it to the DNA sequences of 10 wild boars hailing from Asia and Europe. They also compared the pig genome to genomes from humans, mice, dogs, horses and cows.
The results were published in the journals Nature and the Proceedings of the National Academy of Sciences on Wednesday.
"This new analysis helps us understand the genetic mechanisms that enable high-quality pork production, feed efficiency and resistance to disease," Sonny Ramaswany, the director of the U.S. Department of Agriculture's National Institute of Food and Agriculture, said in a statement Wednesday. "This knowledge can ultimately help producers breed high-quality swine, lower production costs and improve sustainability."
One interesting tidbit is that pigs have more genes related to smell than humans, mice or dogs -- which is not surprising when you think of truffle-hunting pigs. One would think that with such a perceptive nose, the pig would be a picky eater. But the genetic analysis also found that pigs have significantly fewer taste receptors for bitter flavors, which may be why they can eat things that we would find disgusting.
"Understanding the genes that shape the characteristics of pigs can point to how and why they were domesticated by humans," Archibald said. "Perhaps it was their ability to eat stuff that is unpalatable to us humans."
Scientists found 112 places in the pig genome where a porcine protein contains an element that is linked to diseases in humans. They found protein aberrations linked to dyslexia, Parkinson's disease, Alzheimer's disease, and obesity, just to name a few.
The researchers were also trying to map the pig genome's endogenous retroviruses, or ERVs. These are genetic traces left behind after a retrovirus like HIV infects a host and integrates itself into the genomes of cells.
Pigs turn out to have fewer ERVs than people. But unlike the ERVs found in humans, some pig ERVs can still reproduce and spread. This could pose a potential risk to transplant recipients that receive genetically modified pig organs. Growing human organs in pigs has been floated as a possible solution to the shortage of desperately needed organs.
On the evolution front, scientists found that the European and Asian wild boars have genetically diverged enough since they separated 1 million years ago to such an extent that they are basically subspecies now. Researchers have also zeroed in on three genetic regions that are thought to play a role in one of the biggest differences between domestic and wild pigs: the tame pigs' have a much longer back, which has more vertebrae.
"This study demonstrates the benefits of basic genomic research on agricultural animals and their closest living relatives," University of Illinois president and animal sciences professor emeritus Bob Easter said in a statement Wednesday. "This work has important implications for agriculture, contributes to our understanding of evolution and will aid in human medicine.”
SOURCES: Groenen et al. “Analyses of pig genomes provide insight into porcine demography and evolution.” Nature 491: 393-398; Rubin et al. “Strong signatures of selection in the domestic pig genome.” Proceedings of the National Academy of Sciences published online 14 November 2012.