Coding-sequence variability in TLR4 in tropical and temperate zone passerines

Toll-like receptor 4 (TLR4) is an innate immunity receptor important for recognition of bacterial lipopolysaccharide in vertebrates. Generally, Toll-like receptors (TLRs) which bind conservative microbe-associated molecular patterns (MAMPs) represent proteins evolving under strong purifying selection. However, it has been repeatedly shown that even MAMPs are structurally variable and this can be particularly true for pathogens occurring in different latitudes. The environmental conditions in the tropics are suitable for the development of higher species diversity than in the temperate zone. According to the hypothesis, the tropical and migratory birds are exposed to higher pathogen diversity than their closely related temperate zone species, and thus should have also higher TLR4 variability. Here, we have selected 21 tropical and 25 temperate zone passerine species which represent 26 families throughout passerine phylogeny. Using 454-pyrosequencing approach, all 675 individuals (15 individuals per species) were sequenced on the 681 bp long Ligand-binding region of TLR4. In this contribution we provide first preliminary results on intra- and interspecific comparison of TLR4 variability in passerines.