Ninghai Institute of Mariculture Breeding and Seed Industry, Zhejiang Wanli University, Ningbo, China.
Zhejiang Key Laboratory of Aquatic Germplasm Resource, Zhejiang Wanli University, Ningbo, China.
Front Immunol. 2022 Jun 1;13:907274. doi: 10.3389/fimmu.2022.907274. eCollection 2022.
Family I84 protease inhibitors represent a novel family in the MEROPS peptidase database and are likely unique for molluscan host defense. Two Family I84 members, and , were reported from the razor clam in a previous research. In the present study, 12 additional genes, named to , were identified genome wide sequence analyses. Among them, 10 genes were predicted to have a signal sequence, but one () was not. Besides, one sequence () was likely to encode a prematurely terminated peptide. The predicted mature peptides shared characteristics including 12 conserved cysteine residues, isoelectric points of 4.98 to 6.11, and molecular weights of 7.1 to 9.3 kDa with previously reported family members. Four motifs were characterized in 13 predicted mature peptides (with exception of scSI-14), which shared two to four conserved cysteine residues, are possibly to form two functional domain comprised 6 cysteine residues, respectively. At genomic level, all the 14 razor clam Family I84 genes were organized into 3 exons and 2 introns; 13 of them clustered in 3 regions of 100 kb on 3 separate chromosomes, suggesting tandem duplications of related genes. The promoter region of all the 14 genes was predicted to share some transcription factor binding sites, in particular those responsive to pathological and physiological stimuli, but no shared motifs were identified. Analyses also revealed differences in expression patterns among the genes. One gene in a tandem duplicated gene pairs usually showed a higher expression level than the other whereas non-tandem duplicated genes exhibited a higher degree of correlation in expression level. In addition, 8 of the 14 genes demonstrated higher level of expression in tolerant clams than in non-tolerant clams following challenges with These results generated important information about the evolution of Family I84 protease inhibitors in .
家族 I84 蛋白酶抑制剂是 MEROPS 肽酶数据库中的一个新家族，可能是软体动物宿主防御的特有产物。在之前的一项研究中，从 razor clam 中报道了两种家族 I84 成员和。在本研究中，通过全基因组序列分析鉴定了 12 个额外的基因，命名为至。其中，10 个基因被预测具有信号序列，但一个（）没有。此外，一个序列（）可能编码一个过早终止的肽。预测的成熟肽具有 12 个保守半胱氨酸残基、等电点为 4.98 至 6.11 和分子量为 7.1 至 9.3 kDa 的特征，与之前报道的家族成员相似。在 13 个预测的成熟肽中（除了 scSI-14 外），有 4 个特征基序，它们共享 2 到 4 个保守的半胱氨酸残基，可能分别形成由 6 个半胱氨酸残基组成的两个功能域。在基因组水平上，14 个 razor clam 家族 I84 基因都被组织成 3 个外显子和 2 个内含子；其中 13 个基因聚集在 3 条独立染色体的 100kb 区域的 3 个区域，表明相关基因的串联重复。所有 14 个基因的启动子区域被预测共享一些转录因子结合位点，特别是那些对病理和生理刺激有反应的位点，但没有鉴定到共同的基序。分析还揭示了基因之间表达模式的差异。在串联重复基因对中，一个基因通常比另一个基因表达水平更高，而非串联重复基因的表达水平相关性更高。此外，在耐受 clam 中，有 8 个基因在受到刺激后表达水平高于非耐受 clam，而在耐受 clam 中，有 8 个基因在受到刺激后表达水平高于非耐受 clam。这些结果提供了关于家族 I84 蛋白酶抑制剂在 razor clam 中的进化的重要信息。
