Haemonchus contortus could enter the diapause stage to avoid hostile conditions, however the inducing mechanism still remains poorly understood. A similar dauer strategy exists in Caenorhabditis elegans, and dauer phenomones, which are produced through a four step cycle of peroxisomal fatty acid β-oxidation, are essential in this stage. In this study, a novel gene, Hc-dhs-28, was identified and characterised. Hc-DHS-28 was the homologue of Ce-DHS-28, a key enzyme in the oxidation cycle, and the protein contained a short chain dehydrogenase domain and a peroxisomal targeting signal 1. The expression pattern of Hc-DHS-28 detected by quantitative real-time PCR and indirect immunofluorescence assay revealed that this protein was mainly expressed in the intestine and subdermal regions of larvae at diapause and in free-living stages. Enzyme activity analysis confirmed its 3-hydroxyacyl CoA dehydrogenase activity with 121, 149, 162 and 166 as key functional sites; meanwhile co-localization in human embryonic kidney 293 cells indicated that Hc-DHS-28 was targeted to the peroxisome of cytoplasm under the guide of peroxisomal targeting signal 1, which was consistent with the functional domain prediction of Hc-dhs-28. Overexpression, rescue and RNA interference experiments were carried out to explore the function of Hc-dhs-28. Our results showed that Hc-dhs-28 was very similar to Ce-dhs-28 and partially rescued its function in C. elegans. RNAi with Hc-dhs-28 in C. elegans led to decreased transcription of genes in the peroxisomal fatty acid β-oxidation cycle, considerable fat accumulation and dauer formation defects. Furthermore, immunisation with recombinant Hc-DHS-28 protein in sheep was able to maintain the body weight of the host after infection and reduce the worm burden. In conclusion, Hc-DHS-28 is most likely involved in the peroxisome fatty acid β-oxidation as the third 3-hydroxyacyl CoA dehydrogenase to regulate the production of diapause-related pheromones, and then influence the formation of diapause in H. contortus.

Haemonchus contortus可以进入滞育阶段以避免不利条件，但是诱导机制仍然知之甚少。秀丽隐杆线虫中存在类似的 dauer 策略，并且通过过氧化物酶体脂肪酸 β-氧化的四步循环产生的 dauer 现象在此阶段是必不可少的。在这项研究中，一个新基因Hc-dhs-28，被识别和表征。Hc-DHS-28 是氧化循环中的关键酶 Ce-DHS-28 的同源物，该蛋白含有一个短链脱氢酶结构域和一个过氧化物酶体靶向信号 1。通过检测 Hc-DHS-28 的表达模式实时定量 PCR 和间接免疫荧光分析表明，该蛋白主要在滞育和自由生活阶段的幼虫的肠道和皮下区域表达。酶活性分析证实其3-羟酰基辅酶A脱氢酶活性以121、149、162和166为关键功能位点；同时在人胚肾293细胞中的共定位表明Hc-DHS-28在过氧化物酶体靶向信号1的指导下靶向细胞质的过氧化物酶体，这与功能域预测一致Hc-dhs-28。进行过表达、拯救和RNA干扰实验以探索Hc-dhs-28的功能。我们的结果表明Hc-dhs-28与Ce-dhs-28非常相似，并且部分挽救了它在秀丽隐杆线虫 中的功能。RNAi的与HC-DHS-28在秀丽隐杆线虫导致过氧化物酶体脂肪酸β-氧化循环中基因的转录减少，大量脂肪积累和多尔形成缺陷。此外，在绵羊中使用重组 Hc-DHS-28 蛋白进行免疫能够维持感染后宿主的体重并减少蠕虫负担。总之，HC-DHS-28是最有可能参与过氧化物酶体脂肪酸β氧化作用作为第三3-羟基酰基-CoA脱氢酶规范生产滞育相关的信息素的，进而影响滞育的地层中的捻转血矛线虫。