State Key Laboratory of Rice Biology & Ministry of Agriculture Key Lab of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, 310058, China.
Division of Plant Sciences, College of Agriculture, Food and Natural Resources, University of Missouri, Columbia, Missouri, USA.
Sci Rep. 2017 Nov 16;7(1):15755. doi: 10.1038/s41598-017-16000-5.
Serine protease inhibitors (SPIs) regulate protease-mediated activities by inactivating their cognate proteinases, and are involved in multiple physiological processes. SPIs have been extensively studied in vertebrates and invertebrates; however, little SPI information is available in parasitoids. Herein, we identified 57 SPI genes in total through the genome of a parasitoid wasp, Pteromalus puparum. Gene structure analyses revealed that these SPIs contain 7 SPI domains. Depending on their mode of action, these SPIs can be categorized into serpins, canonical inhibitors and alpha-2-macroglobulins (A2Ms). For serpins and canonical inhibitors, we predicted their putative inhibitory activities to trypsin/chymotrypsin/elastase-like enzymes based on the amino acids in cleaved reactive sites. Sequence alignment and phylogenetic tree indicated that some serpins similar to known functional inhibitory serpins may participate in immune responses. Transcriptome analysis also showed some canonical SPI genes displayed distinct expression patterns in the venom gland and this was confirmed by quantitative real-time PCR (qPCR) analysis, suggesting their specific physiological functions as venom proteins in suppressing host immune responses. The study provides valuable information to clarify the functions of SPIs in digestion, development, reproduction and innate immunity.
丝氨酸蛋白酶抑制剂（SPIs）通过使靶蛋白酶失活来调节蛋白酶介导的活性，并且参与多种生理过程。SPIs 在脊椎动物和无脊椎动物中得到了广泛的研究；然而，在寄生虫中，SPIs 的信息很少。本文通过寄生蜂蛹期长尾小蜂的基因组共鉴定了 57 个 SPI 基因。基因结构分析表明，这些 SPIs 包含 7 个 SPI 结构域。根据作用方式的不同，这些 SPI 可分为丝氨酸蛋白酶抑制剂、经典抑制剂和α-2-巨球蛋白（A2M）。对于丝氨酸蛋白酶抑制剂和经典抑制剂，我们根据切割反应性位点中的氨基酸预测了它们对胰蛋白酶/糜蛋白酶/弹性蛋白酶样酶的潜在抑制活性。序列比对和系统发育树表明，一些类似于已知功能抑制丝氨酸蛋白酶抑制剂的丝氨酸蛋白酶可能参与免疫反应。转录组分析还显示，一些经典 SPI 基因在毒液腺中表现出不同的表达模式，这通过定量实时 PCR（qPCR）分析得到了证实，表明它们作为抑制宿主免疫反应的毒液蛋白具有特定的生理功能。该研究为阐明 SPIs 在消化、发育、繁殖和先天免疫中的功能提供了有价值的信息。
