TLRs (Toll-like receptors) are essential in host defense against pathogens. There are two types of TLR5, namely, membrane form of TLR5 (TLR5M) and soluble form of TLR5 (TLR5S), both of which perform a crucial role in flagellin response. TLR13 is a TLR that localizes to endosomes and recognizes nucleic acids released by internal microorganisms, including viruses, bacteria, and fungi. Here, the full-length coding sequence (CDS), protein structure, and immune response and subcellular localization of TLR5 (TLR5S) and TLR13 were characterized in large yellow croaker (Larimichthys crocea). These TLRs share high sequence homology with other ichthyic TLRs, while also having their own characters; qtPCR was determined and the results found that the three genes were constitutively expressed in all examined tissues: TLR5M was highly expressed in the spleen and liver; TLR13 expression was high in the kidney, liver, and spleen. And TLRs were upregulated following stimulation with Vibrio parahaemolyticus in the liver, spleen, and kidney. Immunofluorescence staining revealed that TLR5M were localized in the cytoplasm, while TLR5S and TLR13 were in the endosome. The evolutionary analysis has shown that TLR13 was clustered with TLR11, 19, 20, 21, and 22, while TLR5 and TLR3 were classified into a group; these results suggest that TLRs are vital in the defense of L. crocea against bacterial infection and further increase our understanding of TLR function in innate immunity in teleosts.

中文翻译：

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基于大嘴猴（Larimichthys crocea）基因组数据的两种形式的TLR5和TLR13基因的分子表征和进化分析

TLR（Toll样受体）在宿主防御病原体中至关重要。TLR5有两种类型，即TLR5的膜形式（TLR5M）和TLR5的可溶形式（TLR5S），两者在鞭毛蛋白反应中均起关键作用。TLR13是一种TLR，定位于内体并识别由内部微生物（包括病毒，细菌和真菌）释放的核酸。在这里，在大型黄花鱼（Larimichthys crocea）中表征了TLR5（TLR5S）和TLR13的全长编码序列（CDS），蛋白质结构以及免疫应答和亚细胞定位）。这些TLR与其他鱼鳞TLR具有高度的序列同源性，同时也具有自己的特征。确定了qtPCR，结果发现这三个基因在所有检查的组织中组成性表达：TLR5M在脾脏和肝脏中高表达；而TLR5M在脾脏和肝脏中高表达。TLR13在肾脏，肝脏和脾脏中高表达。副溶血性弧菌刺激肝脏，脾脏和肾脏后，TLRs上调。免疫荧光染色显示TLR5M位于细胞质中，而TLR5S和TLR13位于内体中。进化分析表明，TLR13与TLR11、19、20、21和22聚在一起，而TLR5和TLR3分为一组。这些结果表明，TLR在防御大隐菌中至关重要 抵抗细菌感染，并进一步增进我们对硬骨鱼先天免疫中TLR功能的了解。