Abstract

Host defense against infectious disease is a tormenting task considering not only the enormous pathogens diversity, but also their rapid genome replication and mutation rates. Front line and anti-microbial defense is accomplished by the innate immune system with the help of pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) in prompt pathogens detection. In this study, distribution of single nucleotide polymorphisms (SNPs) in TLR2 gene was studied in two cattle breeds Dhanni and locally adapted exotic Jersey. The complete sequences of TLR2 gene composed of 5'UTR 136 bp, coding sequence 2355 bp and 3'UTR 1316 bp. Phylogenetic analysis revealed clustering of Dhanni with Bos indicus and Jersey with Bos taurus as the nearest neighbor. Sequencing of TLR2 in Dhanni cattle showed the occurrence of 35 variable sites within coding region including 37% non-synonymous and 63% synonymous, while in Jersey cattle, 21 SNPs were identified within coding region including 48% non-synonymous and 52% synonymous. Mostly SNPs fell within the leucine-rich repeats (LRR) of extracellular domain, regions responsible for ligand recognition. The ratio of d_S/d_N substitutions was <1 at polymorphic-sites indicating purifying selection. The SNPs at position 681 (p.Leu227Phe in Jersey) and 521(p.Thr174Ile in Dhanni) were presumed to have possible damaging or functional altering effect. The predicted bovine TLR2 is a solenoid-like (coil-like) built from 20 LRRs bend into a horseshoe shaped structure. The polymorphisms in TLR2 can be useful in future research exploring its role in immunity and may be used as markers for disease resistance under selective breeding.

中文翻译：

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Dhanni和Jersey牛品种的Toll-like Receptor2基因中基于序列的结构和多态性进化。牛TLR2中的遗传多态性

摘要

考虑到巨大的病原体多样性，还要考虑其快速的基因组复制和突变率，宿主对传染病的防御是一项艰巨的任务。前线免疫和抗微生物防御功能是通过先天免疫系统在模式病原体检测中借助模式识别受体（PRR）（例如Toll样受体（TLR））来完成的。在这项研究中，TLR2基因中的单核苷酸多态性（SNPs）的分布研究了两个牛品种Dhanni和本地适应的外来泽西岛。TLR2基因的完整序列由5'UTR 136 bp，编码序列2355 bp和3'UTR 1316 bp组成。系统发育分析表明，Dhanni与Bos indicus成簇，泽西与Bos金牛座成簇。作为最近的邻居。Dhanni牛中TLR2的测序显示在编码区内有35个可变位点，包括37％的非同义和63％的同义，而在泽西牛中，在编码区内鉴定出21个SNP，包括48％的非同义和52％的同义。大多数SNP落在胞外域的富亮氨酸重复序列（LRR）中，该区域负责配体识别。的比率d_小号/ d _Ñ多态性位点的取代度<1，表明纯化选择。推测在位置681（泽西岛的peu.Leu227Phe）和在位置521（dhanni的p.Thr174Ile）的SNP具有可能的破坏或功能改变作用。预测的牛TLR2是由20个LRR弯曲成马蹄形结构构成的螺线管状（线圈状）。TLR2中的多态性可用于将来的研究中，探索其在免疫中的作用，并可作为选择性育种下抗病性的标记。