饲料中添加酵母提取物对凡纳滨对虾免疫相关基因表达及抗菌机能的影响

Effects of dietary yeast extract supplementation on the immune-related gene expressions and vibrio-resistant ability in Litopenaeus vannamei

为了评估饲料中添加酵母提取物对凡纳滨对虾免疫灵敏性和平衡性的相关基因表达的影响,以鱼粉含量为24.5%的基础饲料(对照组)及在基础饲料中添加2.5%酵母提取物的实验饲料,分别饲喂凡纳滨对虾56 d,检测两种饲料投喂的对虾在急性感染溶藻弧菌前后鳃组织Toll受体、IM D和溶菌酶mRNA表达量变化及感染后的对虾死亡情况。结果表明:摄食添加酵母提取物饲料的凡纳滨对虾鳃组织中Toll受体mRNA和溶菌酶mRNA表达量均显著高于对照组对虾(P<0.05),IMD mRNA表达量与对照组无显著性差异(P>0.05)。急性感染溶藻弧菌后,两组对虾鳃组织Toll受体、IMD和溶菌酶mRNA表达量随感染进程均出现显著变化,Toll受体、IMD和溶菌酶mRNA表达量峰值出现的时间分别为24、42和36 h,且摄食添加酵母提取物组对虾各基因的表达量峰值分别为对照组峰值的201.06%、481.46%和276.77%,均显著高于对照组对虾(P<0.05)。摄食添加酵母提取物饲料组对虾鳃组织中Toll受体和IM D mRNA表达量在感染溶藻弧菌后12和24 h分别出现显著上调,而对照组对虾鳃组织中Toll受体和IMD mRNA表达量分别在感染弧菌后24和42 h才出现显著上调。两组对虾经溶藻弧菌人工急性感染后72 h内的累积死亡率无显著差异(P>0.05)。实验表明,饲料中添加酵母提取物上调了溶藻弧菌感染前凡纳滨对虾Toll受体和溶菌酶mRNA的表达量,提早了溶藻弧菌感染后对虾Toll受体和IMD mRNA表达量上调时间,且增加了对虾Toll受体、IM D和溶菌酶mRNA表达量的峰值,在一定程度上提高了凡纳滨对虾免疫相关基因表达的灵敏性。

The basal diet containing 24.5 % fish meal as control, and experiment diet （ YE group） with 2.5 % yeast extract in basal diet, were fed to the white shrimp Litopenaeus vannamei respectively for 56 d, then the mRNA expression levels of Toll receptor, IMD and lysozyme in gills and Vibrio-resistance of the both shrimp were detected for assessing the effect of dietary yeast extract on sensitivity and balance of immunerelated gene expression of shrimp. The results showed that：The shrimp fed the experiment diet displayed significantly increased mRNA expressions of Toll receptor and lysozyme in gills compared with the shrimp fed the control diet（P 〈 0.05 ）. There was no significant difference in IMD mRNA expression level in gills between YE group and the control（ P 〉 0.05 ）. The relative mRNA expression levels of Toll receptor, IMD and lysozyme of the two groups changed significantly after Vibrio alginolyticus challenge,and the peak of the gene expressions appeared at 24,42 and 36 h respectively in both groups. The peaks of the gene expression of Toll receptor, IMD and lysozyme in YE group were 201.06% ,481.46% and 276.77% of those in the control, and significantly higher than those in the control （ P 〈 0.05 ）. The mRNA expression levels of Toll receptor and IMD in YE group significantly up-regulated at 12 and 24 h respectively while at 24 and 42 h respectively in the control after Vibrio challenge. There was no significant difference in 72 h cumulative mortality after V. alginolyticus infection between the two groups. It is therefore suggested that yeast extract added in diet significantly up-regulated the relative mRNA expression levels of Toll receptor and lysozyme in gills of L. vannamei before V. alginolyticus challenge,led to significant up-regulations of the relative mRNA expression levels of Toll receptor and IMD early and increased the peaks of the relative mRNA expression levels of Toll receptor, IMD and lysozyme in gills of the shrimp after V. alginolyticus challenge. This result implied that dietary yeast extract improved the sensitivity of the immune related genes expression of the shrimp to some extent.