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Abstract：
Heat shock protein 70 (Hsp70), a highly conserved protein family, is widely distributed in organisms and plays fundamental roles in biotic and abiotic stress responses. However, reports on Hsp70 genes are scarce in microsporidia, a very large group of obligate intracellular parasites that can infect nearly all animals, including humans. In this study, we identified 37 Hsp70 proteins from eight microsporidian genomes and classified them into four subfamilies (A-D). The number of Hsp70 genes in these microsporidia was significantly fewer than in Rozella allomycis and yeast. All microsporidian species contained genes from each subfamily and similar subcellular locations (mitochondria, endoplasmic reticulum, cytosol, and cytosol and/or nucleus), indicating that each Hsp70 member may fulfil distinct functions. The conserved structures and motifs of the Hsp70 proteins in the same subfamily were highly similar. Expression analysis indicated that the subfamily C cytosol (cyto)-associated Hsp70s is functional during microsporidia development. Immunofluorescence assays revealed that Cyto-NbHsp70 was cytoplasmically located in the proliferation-stage of Nosema bombycis. Cyto-NbHsp70 antiserum also labeled Encephalitozoon hellem within infected cells, suggesting that this antiserum is a potential molecular marker for labeling the proliferative phases of different microsporidian species. The propagation of N. bombycis was significantly inhibited following RNAi of Cyto-NbHsp70, indicating that Cyto-NbHsp70 is important for pathogen proliferation. Our phylogenetic data suggest that Hsp70 proteins evolved during microsporidia adaption to intracellular parasitism, and they play important roles in pathogen development.
摘要：
热休克蛋白70(Hsp70),一个高度保守的蛋白质家族，在生物体中广泛分布，在生物和非生物胁迫反应中起着重要作用。然而,关于Hsp70基因的报道在微孢子虫中很少，一个非常大的专性细胞内寄生虫，可以感染几乎所有的动物，包括人类。在这项研究中,我们从8个小孢子虫基因组中鉴定出37种Hsp70蛋白,并将它们分为4个亚家族(A-D).这些微孢子虫中Hsp70基因的数量明显少于Rozellaallomycis和酵母。所有微孢子虫物种都包含来自每个亚家族和相似亚细胞位置的基因（线粒体，内质网，胞质溶胶,和胞质溶胶和/或细胞核)，表明每个Hsp70成员可以履行不同的职能。同一亚家族中Hsp70蛋白的保守结构和基序高度相似。表达分析表明，亚家族C胞质溶胶（cyto）相关的Hsp70在微孢子虫发育过程中具有功能。免疫荧光测定显示，Cyto-NbHsp70在细胞质中位于家蚕Nosema的增殖阶段。Cyto-NbHsp70抗血清还标记了受感染细胞内的头孢菌素，表明该抗血清是标记不同微孢子虫物种增殖阶段的潜在分子标记。Cyto-NbHsp70的RNAi后，家蚕原虫的繁殖受到显着抑制，表明Cyto-NbHsp70对于病原体增殖很重要。我们的系统发育数据表明，Hsp70蛋白在微孢子虫适应细胞内寄生过程中进化，它们在病原体的发育中起着重要作用。
