Toll-like receptor 21 (TLR21) is a non-mammalian type TLR, and plays an important role in innate immune response in fish. In this paper, the full-length cDNA sequence of TLR21 gene was identified and characterized from large yellow croaker, Larimichthys crocea and was termed as Lc TLR21. It consists of 3365 bp, including a 5’-terminal untranslated region (UTR) of 97 bp, a 3’-terminal UTR of 331 bp, and an open reading frame (ORF) of 2937 bp encoding a polypeptide of 978 amino acid residues. The deduced Lc TLR21 contains a signal peptide domain at N-terminal, 12 leucine-rich repeats (LRRs) at the extracellular region, a transmembrane domain and a cytoplasmic toll-interleukin-1 receptor (TIR) domain at the C-terminal. Subcellular localization analysis revealed that the Lc TLR21-GFP was constitutively expressed in cytoplasm. Tissue expression analysis indicated that Lc TLR21 gene broadly expressed in most of the examined tissues, with the most predominant abundance in spleen, followed by head-kidney and liver, while the weakest expression was detected in brain. The expression level of Lc TLR21 after LPS, poly I:C and Vibrio parahaemolyticus challenges was investigated in spleen, head-kidney and liver. Lc TLR21 gene transcripts increased significantly in all examined tissues after the challenges, and the highest expression level was detected in liver at 24 h after poly I:C stimulation ( P < 0.05), suggesting that Lc TLR21 might play a crucial role in fish resistance to viral and bacterial infections.

中文翻译：

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大 黄鱼 TLR21的亚细胞定位 及其在免疫反应中的基因表达分析。

Toll样受体21（TLR21）​​是非哺乳动物型TLR，在鱼类的先天免疫应答中起重要作用。本文从大型黄花鱼（ Larimichthys crocea ）中鉴定并鉴定了TLR21基因的全长cDNA序列， 被称为 Lc TLR21。它由3365 bp组成，包括97 bp的5'末端非翻译区（UTR），331 bp的3'末端UTR和2937 bp的开放阅读框（ORF），编码978个氨基酸残基的多肽。推导的 LC TLR21在N端包含一个信号肽域，在细胞外区域包含12个富含亮氨酸的重复序列（LRR），在C端包含一个跨膜域和一个胞质收费白介素1受体（TIR）域。亚细胞定位分析表明， LC TLR21-GFP在细胞质中组成性表达。组织表达分析表明， Lc TLR21基因在大多数受检组织中广泛表达，其中脾脏的丰度最高，其次是头肾和肝脏，而脑中的表达最弱。研究了LPS，poly I：C和 溶血弧菌 攻击后脾脏，头部肾脏和肝脏中 Lc TLR21 的表达水平 。 c 攻击后，所有检查的组织中TLR21基因转录物均显着增加，并且在poly I：C刺激后24 h肝脏中检测到最高的表达水平（ P <0.05），这表明 Lc TLR21可能在鱼的抗性中起关键作用病毒和细菌感染。