Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan.
J Exp Biol. 2013 May 15;216(Pt 10):1905-15. doi: 10.1242/jeb.081240. Epub 2013 Feb 7.
Ticks are obligate hematophagous parasites and important vectors of diseases. The large amount of blood they consume contains great quantities of iron, an essential but also toxic element. The function of ferritin, an iron storage protein, and iron metabolism in ticks need to be further elucidated. Here, we investigated the function a newly identified secreted ferritin from the hard tick Haemaphysalis longicornis (HlFER2), together with the previously identified intracellular ferritin (HlFER1). Recombinant ferritins, expressed in Escherichia coli, were used for anti-serum preparation and were also assayed for iron-binding activity. RT-PCR and western blot analyses of different organs and developmental stages of the tick during blood feeding were performed. The localization of ferritins in different organs was demonstrated through an indirect immunofluorescent antibody test. RNA interference (RNAi) was performed to evaluate the importance of ferritin in blood feeding and reproduction of ticks. The midgut was also examined after RNAi using light and transmission electron microscopy. RT-PCR showed differences in gene expression in some organs and developmental stages. Interestingly, only HlFER2 was detected in the ovary during oviposition and in the egg despite the low mRNA transcript. RNAi induced a reduction in post-blood meal body weight, high mortality and decreased fecundity. The expression of vitellogenin genes was affected by silencing of ferritin. Abnormalities in digestive cells, including disrupted microvilli, and alteration of digestive activity were also observed. Taken altogether, our results show that the iron storage and protective functions of ferritin are crucial to successful blood feeding and reproduction of H. longicornis.
蜱是专性吸血寄生虫，也是疾病的重要传播媒介。它们吸食的大量血液中含有大量的铁，铁是一种必需但也有毒的元素。蜱中铁蛋白的功能和铁代谢需要进一步阐明。在这里，我们研究了一种新鉴定的硬蜱长角血蜱（Haemaphysalis longicornis）分泌的铁蛋白（HlFER2），以及先前鉴定的细胞内铁蛋白（HlFER1）的功能。在大肠杆菌中表达的重组铁蛋白被用于制备抗血清，并检测其铁结合活性。通过 RT-PCR 和 Western blot 分析了不同组织和吸血阶段的蜱的铁蛋白表达情况。通过间接免疫荧光抗体试验证明了铁蛋白在不同组织中的定位。通过 RNA 干扰（RNAi）评估铁蛋白在蜱吸血和繁殖中的重要性。用 RNAi 处理后，还通过光镜和透射电镜检查了中肠。RT-PCR 显示了一些组织和发育阶段基因表达的差异。有趣的是，尽管 HlFER2 的 mRNA 转录水平很低，但仅在产卵期间和卵中检测到 HlFER2。RNAi 导致餐后体重减轻、高死亡率和繁殖力下降。铁蛋白沉默会影响卵黄原基因的表达。还观察到消化细胞的异常，包括微绒毛紊乱和消化活性改变。总之，我们的结果表明，铁蛋白的铁储存和保护功能对长角血蜱的成功吸血和繁殖至关重要。
