r results show that the pig oral repertoire of taste/nutrient receptors consists of at least 28 receptor genes with significant transcription measured for 27. When compared to humans and rodents, the porcine gene sequences encoding sensors for carbohydrates, amino acids and fatty acids were highly conserved whilst the bitter taste gene family showed high divergence. We identified 15 porcine Tas2rs of which 13 are orthologous to human sequences. The single nucleotide polymorphism sequence analysis using 79 pig genomes, representing 14 different breeds/populations, revealed that the Tas2r subset had higher variability than for non-bitter taste genes. In addition, our results show that the difference in nutrient receptor genes between Asian and European breeds accounts for only a small part of the variability, which is in contrast with previous findings involving genome wide data. Conclusions: We have defined twenty-eight oral nutrient sensing related genes for the pig. The homology with the human repertoire is high for the porcine non-bitter taste gene repertoire and low PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19801058 for the porcine Tas2r repertoire. Our data suggests that bitter taste is 
a plastic trait, possibly associated with the ability of pigs to adapt to diverse environments and that may be subject to balancing selection. Keywords: Pig, Nutrition, GPCR, Taste receptor, Bitter, T1R, T2R, SNPs, Population genomics Correspondence: [email protected]; [email protected] Equal contributors 1 Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, 08193 Bellaterra, Spain 3 Centre for Nutrition and Food Sciences, The University of Queensland, St. Lucia 4067, Australia Full list of author information is available at the end of the article 2014 da Silva et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver applies to the data made available in this article, unless otherwise stated. da Silva et al. BMC Genomics 2014, 15:1057 http://www.biomedcentral.com/1471-2164/15/1057 Page 2 of 16 Background The pig, Sus scrofa, appeared in South East Asia ~4.2 million years ago , colonizing a wide range of habitats thereafter including Europe and North Africa. European and Asian wild boars are estimated to have diverged ~1.2 M. The wild boar is among the first of the domesticated livestock species, an event that occurred approximately 8,000-10,000 BC both in Europe and in Asia in independent events. Today, thanks to the intense modern breeding and selection programmes, the pig is one of the most economically important domestic species worldwide providing a relatively cheap source of dietary protein for humans. The species Sus scrofa is highly variable at both the DNA and phenotypic levels and there are 200-300 pig breeds currently DHMEQ supplier recognized. Consequently, the study of pig diversity from different ecosystems and breeds including wild and domestic populations may uncover phenotype-genotype relationships of high evolutionary and adaptive physiology relevance. In particular, dietary adaptation through taste sensory mechanisms is emerging as a major evolutionary selection pressure. Taste receptors and their genes are known to monitor the presence of dietary compounds in the oral cavity. With the exception of the salty and sour tastes,