Screening And Identification Of Candidate Proteins For Meat Quality Traits Of Yak

Yak(Bos grunniens) is mainly distributed in the Qinghai-Tibet Plateau and its adjacent areas. The traditional feeding system and unique environment were proposed to contribute to the various aspects of meat quality. The developed mechanism of meat quality is not yet understood in yak. In order to unravel genetic mechanisms of meat quality, Q-PCR, GC-TOF-MS and i TRAQ were employed to analyze the difference of muscle fiber composion, metabolic and protein markers between the longissimus dorsi muscle of yak and cattle. These studies provide a broad and novel vision of future research at the molecular breeding of yak.1. Compared to cattle, meat of yak had higher PH45 min, a* value, water holding capacity and lower intramuscular fat content and tenderness. Q-PCR was used to analyze the expression of muscle fiber type molecular biomarker(My HC I、My HC IIA、My HC IIX and My HC IIB). The content of types I(oxidative fiber type) was higher in longissimus dorsi muscle of yak compared to that of cattle, while type IIB content was lower. Expression of My HC I had positive correlation with PH45 min, a* value and water holding capacity, and had negative correlation with L* value. Expression of My HC IIA was positive correlated with intramuscular fat content. We concluded that muscle fiber composition can explain in parts the difference of meat quality in yak and cattle.2. Meat quality development is known to depend on post-mortem metabolism. This research adopts GC-TOF-MS techniques to screen the metabolic markers of meat quality traits in longissimus dorsi muscle of yak and cattle. A total of 17 metabolites exhibited differential expression between two groups. Glucose-6-phosphate, 2-hydroxybutanoic acid, myristic acid, linolenic acid, oleic acid, beta-mannosylglycerate, maltose, uridine, fructose, aspartic acid and glutaric acid were up-regulated in the longissimus dorsi muscle of yak, while xanthosine, digitoxose, gluconic acid, nicotinic acid, Ribonic acid, gamma-lactone and beta-glutamic acid were down-regulated. The differential metabolites were mainly involved in glycolysis, nicotinate and nicotinamide metabolism and biosynthesis of unsaturated fatty acids. The content of glucose-6-phosphate was correlated with PH45 min and nicotinic acid was correlated with intramuscular fat content. These results indicated that metabolic intensity of glucose and lipids were different in longissimus dorsi muscle of yak and cattle. Glucose-6-phosphate and nicotinic acid can be used as the metabolic markers for PH45 min and intramuscular fat content, respectively.3. 2-DE and i TRAQ were employed to analyze proteome of longissimus dorsi muscle of yak and cattle. A total of 458 proteins were identified in longissimus dorsi muscle of yak. Most of the proteins were classified as isoelectric point ranged from 4-10. Fifty seven proteins involved in tricarboxylic acid cycle, tryptophan metabolism and fatty acid metabolism were up-regulated in the longissimus dorsi muscle of yak, another 46 proteins involved in glycolysis, pyruvate metabolism and purine metabolism were up-regulated in the longissimus dorsi muscle of cattle. There were 12 proteins correlated with meat quality traits. CAPN1, HSPB6, CRYAB, IDH2, HADH, SOD1 and LDHB were correlated with meat tenderness, PGM1 and ATP5A1 were correlated with PH45 min value, NDUFS2、MDH1 and SOD1 were correlated with intramuscular fat content.