Meeting Abstract
Knowledge of immune systems is largely derived from work on well-established model species such as fruit fly, nematode, mouse, and human. These taxa have been instrumental in developing our current understanding of the molecular underpinnings of innate immunity; however, these species alone do not provide a phylogenetic distribution sufficient for illuminating evolutionary patterns in the evolution of immunity. Toll-like receptors (TLRs) and their associated signaling molecules represent ancient innate immunity mechanisms for pathogen-associated molecular pattern recognition among metazoans. To understand how these mechanisms have evolved and differ in deuterostomes, we sampled TLRs and associated gene across 37 species hemichordates, echinoderms, cephalochordates, tunicates, and vertebrates using transcriptomic and genomic information. Our data reveal the canonical signaling pathway, deemed MYD88-dependent, is conserved among deuterostomes with the single exception of the downstream signaling mediator TAB2. Proteins indicative of specialized/alternative signaling pathways also appear to be present among cephalochordates and hemichordates, despite previous findings suggesting specialized TLR signaling pathways may be specific to the vertebrates. Finally, we find strong phylogenetic support for conserved TLR3 orthologs – the mammalian TLR responsible for binding viral dsRNA – among all deuterostome phyla (except for tunicates which possess a reduced complement of TLRs). This research not only informs the extent of conservation and innovation of deuterostome TLRs, but also strengthens our foundation for understanding the molecular platform on which vertebrate adaptive immunities were established.
