| The flesh quality of fish is affected by many factors.In addition to congenital factors such as species and genetic factors,the breeding environment is one of the main factors affecting meat quality.As an important environmental factor,temperature plays an critical role in the growth and physiological activities of fish.However,whether temperature will affect fish muscle quality and its undelying mechanism is unclear.In this study,the zebrafish(Danio rerio)was used as the research object.A 7-week breeding experiment was carried out with three temperature groups(18 ℃,28 ℃,34 ℃)in triplicate.The present research aimed to explore the effects of temperature on zebrafish muscle nutritional composition,tissue structure,collagen content and possible molecular mechanisms,by analyzing growth performance,body composition and muscle nutritional composition(amino and fatty acids),tissue structure,collagen content and transcriptome changes at different temperatures.Our data would provide a theoretical basis for improving fish meat quality through environmental regulation in aquaculture.The main results are as follows:1.Effects of temperature on growth and muscle nutritional composition of zebrafishFor the growth,the terminal body length and weight were significantly affected by temperature.Terminal body length and weigh of fish in 28 ℃ group were significantly higher than those in 18 ℃ group(p < 0.05).For the whole-body biochemical composition,compared with 28 ℃ group,the water content of 18 ℃ and 34 ℃ groups had no significant difference,while the crude protein and ash content of 18 ℃ groups decreased significantly(p < 0.05).Temperature also significantly affected zebrafish muscle amino acid composition and the content of EAA,NEAA,FAA and TAA(p <0.05).In general,the content of most amino acids in the muscle of 18 ℃ and 34 ℃groups were lower than those of 28 ℃ group(p < 0.05).The contents of Tyr,Ala,Met,Leu,Arg,His and Gly in 34 ℃ group were significantly lower than those in 28 ℃ group(p < 0.05),while only the Pro,Met,Leu and His contents in 18 ℃ group were significantly lower than those in 28 ℃ group(p < 0.05).Meanwhile,EAA,NEAA,FAA and TAA in 34 ℃ group were significantly lower than those in 28 ℃ group(p <0.05),and the contents of NEAA and TAA in 18 ℃ group were significantly lower than those in 28 ℃ group(p < 0.05).Temperature also has a limited effect on muscle fatty acid composition.The content of total saturated fatty acid(SFA)in 18 ℃ and 34 ℃groups was significantly higher than that in 28 ℃ group(p < 0.05).The C16:0 content of 34 ℃ group was significantly higher than that of 28 ℃ group(p < 0.05);and the C18:0 and C18:1T content of 18 ℃ and 34 ℃ groups were significantly higher than those of 28 ℃ group(p < 0.05).2.Effects of temperature on muscle tissue structure and collagen content of zebrafishHistomorphological analysis showed that,compared with 28 ℃,both 18 ℃ and 34 ℃lead to the increase of the average diameter of muscle fibers and decrease of the density of muscle fibers(p < 0.05).By picrosirius red staining analysis,it was found that muscle tissue collagen content was significantly increased in 18 ℃ group(p < 0.05).Furthermore,it was found that the protein expression level of collagen I in the muscle of 18 ℃ group was significantly higher than that of 28 ℃ group and 34 ℃ group by western blot(p < 0.05).These results indicate that temperature significantly affects zebrafish muscle tissue structure and collagen content.3.Effects of temperature on the expression profile of muscle quality-related regulatory genes of zebrafishTo explore the possible mechanism of temperature influencing zebrafish muscle quality,transcriptome sequencing of muscle tissues in different temperature treatment groups was carried out.The DEGs number,GO components and KEGG pathway enrichment among different temperature treatment groups were analyzed.The results showed that the DEGs number increased with the increase of temperature difference.For 18 ℃ vs 28 ℃ group,the enriched KEGG pathways mainly included oxidative phosphorylation,biosynthesis of amino acids,and arginine and proline metabolism;For28 ℃ vs 34 ℃ group,the enriched pathways mainly included aminoacyl-t RNA biosynthesis,RNA transport,and proteasome;For 18 ℃ vs 34 ℃ group,the enriched pathways were mainly involved in ribosome biogenesis in eukaryotes,aminoacyl-t RNA biosynthesis,protein processing in endoplasmic reticulum,RNA transport,and arginine and proline metabolism.Furthermore,the expression patterns of DEGs involved in muscle quality were determined by q RT-PCR,and the results were consistent with transcriptome data.For muscle growth and development related genes,with the increasing of temperature,myf6 expression levels increased significantly,while mef2 cb and myog expression levels decreased significantly(p < 0.05).For arginine and proline metabolism,the expression levels of arg2 decreased significantly with the increasing of temperature,opposite to the expression trend of gatm.The expression levels of pycr1 b in 18 ℃ group was lower than that in 28 ℃ and 34 ℃ groups(p < 0.05).For collagen synthesis genes,the expression levels of the most of collagen genes(col1a1a,col1a2,col2a1 b,etc.)significant decreased with the increasing of temperature(p <0.05).For genes related to collagen metabolism,the expression levels of MMPs(mmp2,mmp9,mmp14 a,mmp14b,mmp15a),TIMP2(timp2a,timp2b)and TGF-β1(tgfb1a,tgfb1b)decreased significantly with the increasing of temperature(p < 0.05);The expression levels of CTGF(ctgfa,ctgfb)decreased significantly in 34 ℃ group(p <0.05);While,the expression levels of SERPINH1(serpinh1a,serpinh1b)increased with the increasing of temperature(p < 0.05).For the protein processing in endoplasmic reticulum pathway,the expression levels of PDIs(p4hb,pdia4),heat shock protein genes(hsp70,hsp40),and sec24 a generally were up-regulated with the increasing of temperature(p < 0.05),opposite to the expression trend of man1b1 b and edem3(p <0.05).These results suggested that temperature may affect muscle quality by regulating the expression of those genes related to muscle growth and development,amino acid metabolism,collagen metabolism and protein processing. |
PDF Full Text Request