Biology Faculty Articles

Document Type

Article

Publication Date

8-12-2019

Publication Title

Diversity

Keywords

Gene gain, Gene loss, Vertebrates, Toll-like receptors, Immune response, Host-pathogen, Positive selection

ISSN

1424-2818

Volume

11

Issue/No.

131

First Page

1

Last Page

25

Abstract

The vertebrate toll-like receptor (TLRs) supergene family is a first-line immune defense against viral and non-viral pathogens. Here, comparative evolutionary-genomics of 79 vertebrate species (8 mammals, 48 birds, 11 reptiles, 1 amphibian, and 11 fishes) revealed differential gain/loss of 26 TLRs, including 6 (TLR3, TLR7, TLR8, TLR14, TLR21, and TLR22) that originated early in vertebrate evolution before the diversification of Agnatha and Gnathostomata. Subsequent dynamic gene gain/loss led to lineage-specific diversification with TLR repertoires ranging from 8 subfamilies in birds to 20 in fishes. Lineage-specific loss of TLR8-9 and TLR13 in birds and gains of TLR6 and TLR10-12 in mammals and TLR19-20 and TLR23-27 in fishes. Among avian species, 5–10% of the sites were under positive selection (PS) (omega 1.5–2.5) with radical amino-acid changes likely affecting TLR structure/functionality. In non-viral TLR4 the 20 PS sites (posterior probability PP > 0.99) likely increased ability to cope with diversified ligands (e.g., lipopolysaccharide and lipoteichoic). For viral TLR7, 23 PS sites (PP > 0.99) possibly improved recognition of highly variable viral ssRNAs. Rapid evolution of the TLR supergene family reflects the host–pathogen arms race and the coevolution of ligands/receptors, which follows the premise that birds have been important vectors of zoonotic pathogens and reservoirs for viruses.

Comments

©2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Additional Comments

Fundação para a Ciência e a Tecnologia grant #s: SFRH/BD/48518/2008, SFRH/BD/79766/2011, SFRH/BD/134565/2017; Russian Science Foundation grant #: 17-14-01138; Genome Russia Grant #: 1.52.1647.2016; FCT and European Structural and Investment Fund: COMPETE 2020; FCT National Funds project #: PTDC/CTA-AMB/31774/2017 (POCI-01-0145-FEDER/031774/2017).

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

ORCID ID

0000-0001-7353-8301

ResearcherID

N-1726-2015

DOI

10.3390/d11080131

Peer Reviewed

Find in your library

Included in

Biology Commons

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.