Toll-like receptors are a family of conserved membrane receptors which are involved in the regulation of a series of innate immune responses in invertebrates and vertebrates. Two different types of Toll-like receptors from giant freshwater prawn (Macrobrachium rosenbergii), which were designated as MrToll1 and MrToll2, were cloned in the present study. The full-length cDNA of MrToll1 is 4234 bp in length, which includes a 3015-bp open reading frame (ORF) encoding a deduced protein of 1004 amino acids. The sequence of MrToll2 cDNA is 4383 bp in length containing a 2739-bp ORF which encodes 912 amino acid residues. The results from the multiple alignments of amino acid sequences and phylogenetic analysis indicated the two MrTolls identified in the present study should be classified as crustacean type-1 and type-2 Toll-like receptor, respectively. MrToll1 and MrToll2 were constitutively expressed in all the examined tissues, including gill, stomach, intestine, eyestalk, muscle, heart, ganglion, brain, hemocytes and hepatopancreas. RNA interference assay demonstrated that knockdown of MrToll1 with specific-siRNA significantly suppressed the expression of myeloid differentiation factor 88 (MyD88), anti-lipopolysaccharide factor (ALF), crustin and prophenoloxidase (proPO) and enhanced the expression level of MrToll2 in M. rosenbergii. Additionally, an obvious down-regulation of MyD88 and crustin expression was observed in MrToll2-silenced prawns. These findings suggest that MrToll1 and MrToll2 might play essential roles in the innate immunity of M. rosenbergii through regulating the expression of immune-related genes.

Toll样受体是一类保守的膜受体，参与无脊椎动物和脊椎动物一系列先天免疫应答的调节。来自淡水虾的两种不同类型的Toll样受体（罗氏沼虾）），分别命名为MrToll1和MrToll2，在本研究中被克隆。MrToll1的全长cDNA长度为4234 bp，其中包括一个3015 bp的开放阅读框（ORF），编码1004个氨基酸的推导蛋白。MrToll2 cDNA的序列长度为4383 bp，包含2739 bp的ORF，编码912个氨基酸残基。氨基酸序列的多重比对和系统发育分析的结果表明，在本研究中鉴定的两个MrTolls应该分别分类为甲壳类1型和2型Toll样受体。MrToll1和MrToll2在所有检查的组织中组成性表达，包括g，胃，肠，眼球，肌肉，心脏，神经节，脑，血细胞和肝胰腺。罗氏沼虾。此外，在MrToll2沉默的虾中观察到MyD88和Crustin表达的明显下调。这些发现表明MrToll1和MrToll2可能通过调节免疫相关基因的表达在罗氏沼虾的先天免疫中起重要作用。