Collagens XII and XIV: Two collagen types both associated with bovine muscle and intramuscular lipid metabolism

In continental Europe, intramuscular fat (IMF) content in beef is low but plays a key role in determining flavor. IMF expands inside the extracellular matrix (ECM) of intramuscular connective tissue. This ECM contains among others, collagens XII and XIV, two minor collagens probably involved in muscle metabolism. So, our purpose was to determine if there was an association between the contents in collagens XII and XIV and muscle metabolism. Rectus abdominis (RA, oxidative) and Semitendinosus (ST, oxido-glycolytic) muscles were sampled from steers of two genotypes with high (Angus [Ang], n=10) or low (Limousine [Lim], n=10) intramuscular fat level. Collagens XII and XIV relative abundance was evaluated by Western blot analysis. The characteristic parameters of metabolism were previously measured. Ang muscles contained more collagen XIV than Lim muscles (p<0.001). RA muscle contained more collagen XII than ST muscle (p<0.01). Across the two breeds and muscles, collagen XII was positively correlated with A- and H-fatty acid binding protein (FABP) contents (+0.43 and +0.53, respectively, p<0.05) and activities of three oxidative enzymes (cytochrome-c oxidase: +0.41, isocitrate dehydrogenase [ICDH]: +0.40, citrate synthase [CS]: +0.32) (p<0.05) and collagen XIV was positively correlated with triacylglycerol content (+0.35, p<0.35), A- and H-FABP protein contents (+0.35 and +0.38, respectively, p<0.05) and ICDH (+0.34, p<0.05) and negatively with activities of two enzymes of glycolytic metabolism (phosphofructokinase: -0.31 and lactate dehydrogenase: -0.42, p<0.05). After removing the genotype and muscle effects, only collagen XII remained correlated with A- and H-FABP and CS activity (+0.30, +0.34 and +0.46, respectively, p<0.0505). H-FABP is expressed in various tissues but predominantly in cardiac and oxidative skeletal muscles, whereas A-FABP is exclusively expressed within adipocytes. From these results, we can conclude that collagen XII and XIV are both associated with bovine muscle fiber and intramuscular lipid metabolism, but probably by different mechanisms. As a matter of fact, collagens XII is associated with intramuscular fat differentiation (from its correlation with A-FABP content) and oxidative metabolism (from its correlation with H-FABP content and CS activities) regardless of breed and muscle, whereas type XIV collagen is associated with the same parameters plus enzymes of glycolytic metabolism that discriminate breeds

Genomic regions associated with the nitrogen limitation response revealed in a global wheat core collection

Modern wheat (Triticum aestivum L.) varieties in Western Europe have mainly been bred, and selected in conditions where high levels of nitrogen-rich fertilizer are applied. However, high input crop management has greatly increased the risk of nitrates leaching into groundwater with negative impacts on the environment. To investigate wheat nitrogen tolerance characteristics that could be adapted to low input crop management, we supplied 196 accessions of a wheat core collection of old and modern cultivars with high or moderate amounts of nitrogen fertilizer in an experimental network consisting of three sites and 2 years. The main breeding traits were assessed including grain yield and grain protein content. The response to nitrogen level was estimated for grain yield and grain number per m(2) using both the difference and the ratio between performance at the two input levels and the slope of joint regression. A large variability was observed for all the traits studied and the response to nitrogen level. Whole genome association mapping was carried out using 899 molecular markers taking into account the five ancestral group structure of the collection. We identified 54 main regions involving almost all chromosomes that influence yield and its components, plant height, heading date and grain protein concentration. Twenty-three regions, including several genes, spread over 16 chromosomes were involved in the response to nitrogen level. These chromosomal regions may be good candidates to be used in breeding programs to improve the performance of wheat varieties at moderate nitrogen input levels