Developmental Regularity Of Sheep CAPN1 And CAST Gene MRNA Expression And Their Effect On Meat Quality

The calpain protease system is one of the important endogenous proteolytic enzymes for evaluating the meat qualities and has closely correlation with other characteristics such as flavor and tenderness. It cons is ts in cytoplasm and needs certain Ca2+ to activate. The developmental changes of u-calpain (CAPN1) and calpastain (CAST) gene mRNA level in sheep muscle and their effect on meat tenderness(shear force,water loss rate, marbling and pH)was studied and provided genetic theory foundation for further study calpain protease system to improve meat quality.Male Tan sheep (n=34), Mon-golia sheep (n=31) and small-tailed Han sheep (n=34) at 80 to 200 days old were selected and slaughtered to investigate the shear force,water loss rate, marbling and pH of Longissimus dorsal muscle. Then Longissimus dorsal muscle of three individuals of each breed at different ages were also sampled randomly for determining the developmental changes of CAPN1 and CAST gene mRNA expression by semi-quantitative RT-PCR.The results showed as follows: (1) CAPN1 gene mRNA level and ratio of CAST gene: CAPN gene mRNA level were gradually increased with sheep growth while CAST gene mRNA level was gradually decreased with sheep growth. The CAST gene and CAPN1 gene mRNA level at different ages was significant difference ( p<0.05) and the two genes mRNA level at different breeds was no difference ( p>0.05).(2) shear force increased continuously with sheep growth while marbling and water loss rate were decreased with sheep growth. But the sheep Longissimus dorsal muscle of meat color exhibited'rise-rise-decline'developmental changes from 80th day to the 200th day. The pH of Tan sheep and small tailed Han sheep exhibited'rise-decline-rise'developmental changes from 80th day to the 200th day. But pH of Mon-golia sheep was decrease with growth. The sheep meat quality trait index: water loss rate, meat color, marbling and pH were significant difference at same ages among breeds and at same breeds among ages. The shear force was no significant among ages. But the shear force was significant among breeds. (3) In a whole, the shear force and water loss rate was extremely negative correlation(r =-0.535, p= 0.001), the shear force and pH was negative correlation(r =-0.214,p= 0.035).But the shear force and lightness of meat color was extremely positive correlation(r =0.272, p= 0.007)。Water loss rate and lightness of meat color was extremely negative correlation (r=-0.291, p= 0.004). But water loss rate and marbling was extremely positive correlation(r =0.359, p= 0.000)。But, water loss rate and PH was negative correlation(r =0.201, p= 0.047). (4) In the whole, the CAPN1 gene mRNA level and shear force was negative correlation (r = -0.355, p=0.034) while CAST gene mRNA level and shear force were positive correlation(r =0.372, p= 0.026); But the ratio of CAST gene: CAPN1 gene mRNA level was extremely positive correlation(r = 0.436, p= 0.008) with shear force. CAST gene mRNA level with water loss rate and marbling were also extremely negative relationship(r =-0.427, p = 0.009), (r =-0.548, p = 0.001), respectively. There was positive correlation(r =0.351, p = 0.036) between the CAPN1 gene mRNA level and marbling. But, no such differences were observed in water loss rate and CAPN1 gene mRNA level; Ratio of the two gene with water loss rate and marbling were also extremely negative correlation(r =?0.495, p= 0.002), (r =-0.475, p= 0.003), respectively. CAPN1 gene mRNA level and lightness of meat color was negative correlated (r = -0.389, p=0.019).But CAST gene mRNA level and the ratio of two gene mRNA level was no correlation ( p>0.05) with lightness of meat color. CAPN1, CAST gene mRNA level and the ratio of two gene mRNA level was no correlation (p>0.05) with pH.From the result above, conclusion can be achieved: The developmental changes CAPN1 gene was decreased with sheep growth, but CAST gene mRNA level was gradually increasing with sheep growth. CAPN1 gene mRNA level of Mon-golia sheep was the highest among breeds, CAST gene mRNA level of Mon- golia sheep was the lowest among breeds.There were almost same developmental regularity of Tan sheep, Mon-golia sheep and small-tailed Han sheep meat quality traits. The meat tenderness, juiciness, lightness of meat color and flavor of Mon-golia sheep were the best among three breeds while meat tenderness and flavor of Tan sheep were the worst. Lightness of meat color of Tan sheep was the lowest among three breeds. Marbling, water loss rate and pH may be had a positive effect on meat tenderness. But lighter of meat color of sheep Longissimus dorsal muscle was negative effect on meat tenderness.CAPN1 gene may be have a positive regulatory effect on sheep meat tenderness, lighter of meat color and marbling after slaughtered 3 d. CAST gene and the ratio of CAST gene: CAPN1 gene may be have a negative regulatory effect on meat tenderness, juicing and marbling. Furthermore, the ratio of CAST gene: CAPN1 gene may be had the highest regulatory effect on meat tenderness and juicing.