抗菌肽HBβ-C在全雄和杂交黄颡鱼对多子小瓜虫抗性差异中的作用

THE ROLE OF ANTIMICROBIAL PEPTIDE HBβ-C IN ICHTHYOPHTHIRIUS MULTIFILIIS RESISTANCE IN ALL-MALE AND HYBRID YELLOW CATFISH

  • 摘要: 为研究全雄黄颡鱼(Pelteobagrus fulvidraco)、瓦式黄颡鱼(Pelteobagrus vachelli)和杂交黄颡鱼(黄颡鱼P. fulvidraco♀×瓦氏黄颡鱼P. vachelli♂)对多子小瓜虫(Ichthyophthirius multifiliis)的抗性差异, 通过生物信息学分析黄颡鱼皮肤黏液蛋白质组, 发现其血红蛋白源抗菌肽(HBβ-C)位于血红蛋白β链HBβ的碳端, 共33个氨基酸。利用化学合成的不同浓度的HBβ-C肽段进行体外抗虫实验, 研究发现其能有效杀死滋养体、包囊体和掠食体阶段的多子小瓜虫, 其中15 µg/mL的HBβ-C能在3min内杀死所有滋养体。基因表达量分析显示, 在杂交黄颡鱼的鳃和皮肤组织中, HBβ的mRNA表达量高于全雄黄颡鱼; 但在应对小瓜虫感染的过程中, 全雄黄颡鱼的HBβ mRNA转录水平快速提升, 其表达水平和上升倍率显著高于杂交黄颡鱼。蛋白表达量分析显示, HBβ在全雄黄颡鱼鳃组织中的蛋白表达量明显高于杂交黄颡鱼。免疫荧光定位结果显示, 抗菌肽HBβ-C特异地在红细胞中表达, 可以分泌并附着在滋养体上。综上所述, 相对于杂交黄颡鱼, 全雄黄颡鱼中HBβ具有更高的翻译效率, 可以更高效地应对多子小瓜虫的感染。

     

    Abstract: All-male yellow catfish (Pelteobagrus fulvidraco) and hybrid yellow catfish (P. fulvidraco♀×P. vachelli♂) are the main breeding varieties of yellow catfish. The “white spot disease” caused by Ichthyophthirius multifiliis (Ich) is one of the main diseases of yellow catfish in China. Ich resistance assay was performed on all-male and hybrid yellow catfish, as well as the darkarbel catfish (P. vachelli). By bioinformatics analysis, we identified an antimicrobial peptide HBβ-C from the skin mucus proteome of yellow catfish, a 33 amino acid peptide derived from the C terminal of hemoglobin β chain (HBβ). The anti-parasitic test indicated that HBβ-C effectively killed the trophont, tomont and theront, especially in trophont stage, and 15 µg/mL HBβ-C killed all trophont within 3min. Gene expression analysis showed that the expression of HBβ mRNA in gill and skin of hybrid yellow catfish was higher than that of all-male yellow catfish. Ich challenge significantly increased HBβ mRNA level in all-male yellow catfish, which was higher than that of hybrid yellow catfish. Interestingly, the HBβ protein level in gill of all-male yellow catfish was higher than that in hybrid yellow catfish. Immunofluorescence results showed that the antimicrobial peptide HBβ-C was specifically expressed in red blood cells. After Ich infection, HBβ-C was secreted and attached to the trophont in skin and gill. Thus, our results revealed that all-male yellow catfish was much more resistant to Ich than hybrid yellow catfish. The high HBβ protein in all-male yellow catfish and its ability to kill all stages of Ich might be closely associated with the resistance of all-male yellow catfish to Ich.

     

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