吉富罗非鱼FAS基因的克隆及再投喂和饲料脂肪水平对其表达的影响

Molecular cloning of fatty acid synthase from gift tilapia (Oreochromis niloticus):response of its expression to refeeding and different lipid levels in diet

分离、克隆了吉富罗非鱼脂肪酸合成酶(fatty acid synthase,FAS)基因的部分cDNA片段,共557bp,编码185个氨基酸,序列分析表明吉富罗非鱼FAS与其他物种的相似性为62%～82%。为了研究饲料中脂肪对吉富罗非鱼FAS活性和表达的影响,设置3组含不同脂肪含量的等氮饲料组(3.71%组、7.67%组和16.55%组),饲养90d,禁食48h,测定吉富罗非鱼肝脏中FAS的生物活性,使用实时荧光定量PCR分别测定了饲喂3.71%组、7.67%组和16.55%组饲料的吉富罗非鱼肝脏和肌肉中FASmRNA的表达丰度以及再投喂后6、12、24、48h肝脏中FASmRNA的表达丰度。结果显示,饲料脂肪水平对肝脏中FAS活性无显著影响(P>0.05);肝脏中FASmRNA的表达丰度显著高于肌肉(P<0.05),肝脏和肌肉中FASmRNA的表达丰度随着饲料中脂肪水平增加而显著下降(P<0.05);再次投喂后6～48h,各个组的肝脏中FASmRNA表达丰度显著下降(P<0.05)。结果说明,吉富罗非鱼肝脏中FASmRNA的表达丰度高于肌肉,饲料脂肪水平能够抑制FASmRNA表达,脂肪水平越高抑制作用越明显,再投饲后6～48h,FAS基因的表达受到抑制。

The fatty acid synthase（FAS）was cloned from liver of gift tilapia（Oreochromis niloticus）.The obtained partial cDNA was 557 bp,which encoded 185 amino acids.Compared with other species FAS,the gift tilapia FAS shared 62%-82% identities.To study the FAS activity and gene expression affected by different dietary lipid levels,three groups of different dietary lipid levels（3.71% group,7.67% group and 16.55% group） were set up with the same nitrogen content.After feeding for 90 days,the fish fasted for 48 hours and then the liver FAS activity and FAS mRNA expression level in liver and muscle were studied;Further,the FAS mRNA expression level in liver was examined after refeeding with different lipid level dietary,at 6,12,24,48 hours.Results showed that FAS activity in liver had no significant change with different dietary lipid levels（P〉0.05）.The expression level of FAS mRNA in liver was significantly higher than that in muscle（P〈0.05）.However,the expression level of FAS mRNA in both tissues of liver and muscle was significantly declined with the raising of the dietary lipid level（P〈0.05）.After refeeding for 6 to 48 hours,the expression level of liver FAS mRNA was significantly declined in each group（P〈0.05）.Those results indicated that the expression level of liver FAS mRNA was significantly higher than that in muscle.The dietary lipid level could inhibit the expression level of FAS mRNA,and the tendency is：the higher lipid level,the more obvious inhibition.After refeeding for 6 to 48 hours,the expression of FAS gene was impeded.