Association analysis of single nucleotide polymorphisms in DGAT1, TG and FABP4 genes and intramuscular fat in crossbred Bos taurus cattle.

Previous studies have indicated that single nucleotide polymorphisms (SNPs) in the diacylglycerol-O-acyltransferase1 (DGAT1), thyroglobulin (TG) and adipose fatty acid binding protein (FABP4) genes are associated with intramuscular fat (IMF) levels or marbling scores in beef. The objectives were to estimate the frequency of SNPs in these candidate genes in purebred Irish cattle (n=459) and to determine if individual SNPs are associated with IMF values of longissimus thoracis et lumborum (LTL) and semimembranosus (SM) muscle of crossbred animals (n=138). Results indicated no significant association between the SNPs and IMF, despite the power of this study being sufficient to detect an association with SNPs in the DGAT1 and FABP4 genes. The results confirm the lack of an association found by many other studies and suggest that these SNPs are not influential on the divergent IMF levels in the crossbred population tested.

Lack of an association between single nucleotide polymorphisms in the bovine leptin gene and intramuscular fat in Bos taurus cattle.

Leptin contributes to the regulation of adiposity and metabolism, and single nucleotide polymorphisms (SNPs) in the leptin gene have been associated with intramuscular fat (IMF) levels in beef. Our objectives were to estimate the frequency of four SNPs in the leptin gene in nine purebred cattle (n=430), to test for linkage disequilibrium and infer haplotypes, and to determine if individual genotypes or estimated haplotypes were associated with IMF values in crossbred cattle (n=244). The four SNP loci were found to be in linkage disequilibrium and thus, the frequencies of each of the 16 possible haplotypes were inferred by maximum likelihood. No significant association between any individual SNP and haplotype was found with the divergent IMF values. Our results suggest that these SNPs are not influential on the divergent IMF levels in the crossbred population tested.

Understanding meat quality through the application of genomic and proteomic approaches.

During the past few decades, advances in molecular genetics have led to the identification of multiple genes or genetic markers associated with genes that affect traits of interest in livestock, including single genes of large effect and QTL (genomic regions that affect quantitative traits). Transcriptomics enables analysis of the complete set of RNA transcripts produced by the genome at a given time and provides a dynamic link between the genome, the proteome and the cellular phenotype. Through a functional genomics approach to understanding the molecular basis of meat quality, we can gain further insight into the complex interplay of gene expression events involved in the development of meat quality. Proteomics permits visualisation of the protein content of the cell under varying conditions, combining powerful separation techniques with highly sensitive analytical mass spectrometry. To date, both the human and bovine genome projects have advanced our understanding of gene expression and helped elucidate the function of large portions of the genome. Advantages from this research have permeated through to a broader spectrum of research including that of meat science. Meat quality is manifested through a complexity of events in the muscle and their interactions with many environmental stimuli in both the live animal and during the post-mortem period. A lot of progress has been made in our understanding of the biological processes that contribute to the delivery of consistent quality meat. Through the application of tools of genomics and proteomics we are gaining a deeper insight into these processes and their interaction with environmental factors. Knowledge gained from these approaches can be beneficial in defining and optimising management systems for quality, providing assurance of meat quality and in tailoring quality to suit market needs.

Real-time PCR analysis of carbon catabolite repression of cellobiose dehydrogenase gene transcription in Trametes versicolor.

Cellobiose dehydrogenase production in Trametes versicolor is repressed when additional carbon sources, such as glucose, maltose, galactose, arabinose, and xylose, are added to the fungal cultures growing on cellulose. Real-time quantitative reverse transcription-polymerase chain reaction has been used to demonstrate that the addition of galactose, arabinose, and xylose results in 19-, 92-, and 114-fold reductions, respectively, in cdh transcript levels 96 h post-addition. Glucose exhibits the greatest repressive effect, resulting in a 3400-fold decrease in cdh transcript levels.

Carbon repression of cellobiose dehydrogenase production in the white rot fungus Trametes versicolor is mediated at the level of gene transcription.

Cellobiose dehydrogenase (CDH) production in Trametes versicolor is induced in the presence of cellulose, but decreases when additional carbon sources such as glucose and maltose are added to the fungal cultures. Using T. versicolor-specific cdh primers in a reverse transcription-polymerase chain reaction-based approach, it appears that this repression in CDH production is being mediated at the level of gene transcription. When a 1.6-kb upstream region of the T. versicolor cdh gene was cloned and sequenced, a number of putative CreA-like binding sites were observed. We propose that these sites may be involved in mediating this repressive effect, based on their similarity to the consensus [5'-SYGGRGG-3'] site for binding of the CreA and Cre1 repressor proteins.