Studies On Improvement Of Meat Quality And Related Candidate Genes In Aquatic Animals

As the high-yield and high speed growth in aquaculture industry, the meat quality ofaquatic animals dramatically dropped down. To solve this contradiction,firstly, nutritionalregulation and feed additive formulation method were used to improve the meat quality ofaquatic animals, fish fillet ratio, protein content, and delicious amino acid content wereincreased; fat content, fatty acid composition and proportion were changed, especiallyPUFA content was increased; the main flavor substance IMP content was enhancedsignificantly; the color, taste, and flavor of aquatic animals were all improved in differentdegrees. Secondly, RT-PCR and RACE methods were used to clone the IMP and IMFmetabolism related AMPD1gene and LPL gene, genes structure and function werecharacterized; Real Time PCR method was used to study the mRNA expression indifferent tissues and developmental stages; combined with IMP content by HPLC, IMFcontent by Soxlet extraction, and enzyme activities; relationships among gene expression,enzyme activity, and flavor substances content were established; the metabolicmechanisms of IMP and IMF were explained primarily at molecular level. The mainresults are as follows:In tilapia, fish fillet ratio of experimental group was higher by2.65%than control;the amounts of muscle total amino acids, EAA, and flavor amino acids were all higherthan control, flavor amino acids content was increased by1.41-1.7%; PUFA content ofexperimental group was significantly higher than control, total EPA+DHA were increasedsignificantly, EPA content was increased2times,∑n-3/∑n-6was also higher than control;IMP content of experiment group was increased5-10times than control. In Litopenaeusvannamei, EAA content of experimental group was not improved significantly thancontrol, but flavor amino acids content, including Asp, Glu, and Gly, was increasedsignificantly; PUFA content of experimental group was significantly higher than control, total EPA+DHA were increased significantly,∑n-3/∑n-6was no obvious changes; IMPcontent of experiment group was increased3times than control. Sensory analysis showedthat the shape, color, muscle texture, density, fresh, and odor of experimental animals wereimproved in various degrees than control.Two IMP and IMF metabolism related genes were cloned from Japanese flounder.AMPD1gene was cloned from muscle of flounder (Genebank accession number:JF323023), the full-length cDNA was of2526bp, open reading frame (ORF) was2211bpin length, encoding736AA; LPL gene was cloned from liver of flounder (Genebankaccession number: HQ850701), the full-length cDNA was of2003bp, ORF was1645bp inlength, encoding514AA. Nine tissues were separated from flounder, RT-PCR showed thatthe AMPD1gene was specifically expressed in muscle, whereas not detected in resttissues; LPL gene was ubiquitously expressed in various tissues, highest expressed in theabdominal mesentery tissue, liver, and kidney, and lower in other tissues. AMPD1geneexpression level in muscle of adult fish (750±40g) was significantly higher than juvenile's(7.5±2g)(p<0.05); IMP content in muscle of adult fish (3.35±0.21mg/g) was also higherthan juvenile's(1.08±0.04mg/g)(p<0.05), revealing the important regulatory role ofAMPD1gene in the formation of IMP metabolism. LPL gene expression level and enzymeactivities of both adult and juvenile flounder were lower in muscle than that in liver; LPLgene expression level and IMF content in muscle of juvenile and adult fish showed nosignificant difference; revealing LPL might not be the only major gene for IMFmetabolism in fish muscle, implicating the more function of LPL for participating theregulation of lipids metabolism in fish liver.