Identification and molecular evolutionary analysis of TLR5 gene from the Tibetan macaque (Macaca thibetana)

Abstract

In order to identify the Toll-like receptor 5 (TLR5) as a putative candidate disease-resistance gene in Tibetan macaque (Macaca thibetana), two pairs of primers were designed based on the TLR5 gene sequence of rhesus macaque (Macaca mulatta, NM_001130429). The primers were used to amplify the TLR5 gene from Tibetan macaque, by the polymerase chain reaction (PCR). The compiled sequences were analyzed by bioinformatics. The DNA sequencing and additional combined results showed that the Tibetan macaque TLR5 gene is about 2825 bp and contains an open reading frame of 2577 bp encoding for 858 amino acids. Homology analysis of TLR5 in both species showed that the amino acid and nucleotide identity is about 99.7% and 99.8% and their transmembrane and intracellular domains appeared more conservative than the extracellular domains of proteins. However, re-examining the entire Tibetan macaque TLR5 coding sequence we found that a purifying selection was also acting on the TLR5 gene region encoding for its intracellular domain of the protein. Even though the selection tests indicated that the TLR5 gene experienced a strong purifying selection in the process of evolution, most likely because its potential role in the primate adaptive immune defense, the Tibetan macaque still has the highest relationship with the rhesus macaque.