Muscle Characteristics Comparison And Cloning, Expression Of CAST Gene Between Crisped Grass Carp And Common Grass Carp

Exp.1 Muscle characteristics comparison between crisped grass carp and common grass carpThe differences in physical and chemical characteristics and textural mechanical properties in muscles between 9 grass carps (body weight of 1295.7±37.2g) and 9 crisped grass carps (body weight of 706.8±6.5g) were investigated in the present study. The results indicated that the content of protein in crisped grass carp muscle was higher, while the contents of crude lipid and ferrum were lower than those in grass carp (P<0.05), and there were no significant difference in muscle moisture, crude ash, calcium and chromium contents in both groups. Crisped grass carp had higher pH value, muscle fiber density and collagen content in muscle than those of grass carp (P<0.05). Compared with grass carp, muscle drip loss of crisped grass carp at 2h, 4h, was significantly lower (P<0.05), but not at 8h. The hardness and chewiness of crisped grass carp muscle were higher than those of grass carp in textural mechanical properties (P<0.05). Among meat quality indexes analyzed above, muscle fiber density, pH value and collagen contents played important role to improve the meat quality within a certain range; the contents of lipid showed a negative correlation with muscle hardness (P<0.05), and muscle fiber density showed a negative correlation with muscle drip loss (P<0.05). Combining principal component method, results above showed that contents of lipid and collagen, muscle fiber density and pH value of muscle were important indexes affecting flesh quality of grass carp. Exp.2 Cloning and expression of CAST gene in muscle of crisped grass carp and common grass carpCalpastatin (CAST) is a specific, endogenous inhibitor of the calcium-dependent neutral proteases, calpains, plays a role in muscle growth and meat quality. To skeletal muscles of grass carp (Ctenopharyngodon idellus) as the experimental material, the partial sequences of calpastatin gene was amplified by RT-PCR with degenerate primers designed according to the nucleotide sequence of CAST gene of zebrafish (danio rerio), rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (salmo salar). The calpastatin sequence was 562 bp in length and contained 126 amino acids. The comparison of the deduced amino acids sequence of grass carp CAST cloned with those of zebrafish showed that the amino acid homology was highest (75%) and phylogenetic evolutionary genetic relationship was closest, and CAST were expressed in many tissue of grass carp, including intestines, heart, gills, liver, spleen and brain. The sequencing of cloned sequences of known might be designed specific primers, using fluorescent quantitative PCR method to determine expression of CAST mRNA in muscles of common grass carp and crisped grass carp, and its result showed that CAST mRNA in muscles of crisped grass carp was significantly higher than those of grass carp (P<0.05).