溶藻弧菌感染后凡纳滨对虾鳃组织免疫相关基因的表达

分别给凡纳滨对虾(Litopenaeus vannamei)注射生理盐水、3×10⁶ CFU/mL(低浓度组)和9×10⁶CFU/mL(高浓度组)溶藻弧菌(Vibrio alginolyticus)菌液, 采用荧光定量PCR技术, 检测不同处理后凡纳滨对虾鳃组织中Toll受体、IMD和溶菌酶基因表达量随时间的变化。结果表明, 处理42 h内, 注射生理盐水组对虾的Toll受体和IMD mRNA表达量无显著变化,溶菌酶mRNA表达量在注射36h后显著升高。急性感染溶藻弧菌后,凡纳滨对虾鳃组织中Toll受体、IMD和溶菌酶mRNA的表达量峰值分别出现在感染后24、42和36 h; 溶藻弧菌的感染剂量不影响上述基因表达峰值的出现时间, 但显著影响上述基因的表达峰值(P<0.05), 各基因表达量峰值由大到小均依次为高浓度组、低浓度组、生理盐水组。急性感染初期, 对虾鳃组织中Toll受体mRNA表达量呈现显著下调, 而IMD和溶菌酶mRNA表达量在感染初期不存在显著下调现象。与感染前各基因的表达量相比, 高浓度溶藻弧菌感染组Toll受体mRNA表达量在2 h时显著下调, 低浓度溶藻弧菌感染组Toll受体mRNA表达量在3 h显著下调(P<0.05); 高浓度组IMD和溶菌酶mRNA表达量分别在36 h和12 h时开始有显著上调, 而低浓度组IMD和溶菌酶mRNA表达量则分别在42 h和24 h才有显著上调(P<0.05)。表明溶藻弧菌感染对凡纳滨对虾鳃组织中Toll受体、IMD和溶菌酶mRNA表达量有显著影响, 各基因的表达量与感染进程及溶藻弧菌剂量存在一定的相关性。

Expressions of Toll receptor, IMD and lysozyme mRNA in the gills of the white shrimp (Litopenaeus vannamei) after acute challenge with Vibrio alginolyticus

The relative expression levels of Tollreceptor, immune deficiency (IMD) and lysozyme mRNAs were measured in the gillsof the white shrimp (Litopenaeus vannamei),which were injected with normal saline and differentconcentrations of bacterial suspension (lowconcentration group: 3×10⁶CFU/mL; high concentrationgroup: 9×10⁶CFU/mL) of Vibrio alginolyticus,respectively. The mRNAs were detected quantitatively with real-time PCRtechnology at different times after challenge. Theresults indicated that the relative expression levels of the Tollreceptor and IMD of the shrimp injected with saline did not significantlychange. However, the relative expression levels oflysozyme mRNA significantly increased at 36 h after saline-injection.The peaks of the relative expression of the Toll receptor, IMD and lysozymemRNAs in gills of the shrimps appeared at 24, 42 and 36 h respectivelyafter V. alginolyticus challenge .Thevibrio dosage did not affect the timing of the peak of the gene expressions.However, Vibrio dosage significantly changed sizes of the peaks of geneexpressions (P<0.05). The peaks ofthe gene expression were in the order of high concentration group, the lowconcentration group and the saline-injected group. In the early stage of V. alginolyticus challenge, theexpression level of the Toll receptor, but not IMD and lysozyme mRNA, wassignificantly downregulated. Compared with that before V. alginolyticus challenge, the level of Toll receptor mRNAexpression was significantly lower at 2 and 3 h, respectively, in the high and low concentration group. The IMD and lysozyme mRNAexpression levels of the high concentration group were significantlyupregulated at 36 and 12 h, respectively, after vibriochallenge. The IMD and lysozyme mRNA expression levels of thelow concentration group significantly increased at 42 and 24 h, respectively, after vibrio challenge. The results suggested that the relativeexpression levels of the Toll receptor, IMD and lysozyme mRNA in the gills of L. vannamei were significantly affectedby V. alginolyticus challenge.Changes in the expressions of these genes depended on the challenge time andchallenge dosage of V. alginolyticusto some extent.