title: Diversity and evolution of TIR-domain-containing proteins in bivalves and Metazoa: New insights from comparative genomics.
abstract: The Toll/interleukin-1 receptor (TIR) domain has a fundamental role in the innate defence response of plants, vertebrate and invertebrate animals. Mostly found in the cytosolic side of membrane-bound receptor proteins, it mediates the intracellular signalling upon pathogen recognition via heterotypic interactions. Although a number of TIR-domain-containing (TIR-DC) proteins have been characterized in vertebrates, their evolutionary relationships and functional role in protostomes are still largely unknown. Due to the high abundance and diversity of TIR-DC proteins in bivalve molluscs, we investigated this class of marine invertebrates as a case study. The analysis of the available genomic and transcriptomic data allowed the identification of over 400 full-length sequences and their classification in protein families based on sequence homology and domain organization. In addition to TLRs and MyD88 adaptors, bivalves possess a surprisingly large repertoire of intracellular TIR-DC proteins, which are conserved across a broad range of metazoan taxa. Overall, we report the expansion and diversification of TIR-DC proteins in several invertebrate lineages and the identification of many novel protein families possibly involved in both immune-related signalling and embryonic development.
authors.affiliation: University of Trieste, Department of Life Sciences, Via Licio Giorgieri 5, 34127 Trieste, Italy. Electronic address: mgerdol@units.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Gerdol
authors.affiliation: University of Padova, Department of Biology, Via Ugo Bassi 58/B, 35131 Padova, Italy. Electronic address: paola.venier@unipd.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Venier
authors.affiliation: University of Trieste, Department of Life Sciences, Via Licio Giorgieri 5, 34127 Trieste, Italy. Electronic address: edomi@units.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Edomi
authors.affiliation: University of Trieste, Department of Life Sciences, Via Licio Giorgieri 5, 34127 Trieste, Italy. Electronic address: pallavic@units.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Pallavicini
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D049872:Bivalvia / Q000276:immunology*; D049109:Cell Proliferation; D019143:Evolution, Molecular; D023281:Genomics; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology*; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism*; D017472:Receptors, Interleukin-1 / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000235:genetics / Q000378:metabolism*
chemical_list: D053594:Myeloid Differentiation Factor 88; D017472:Receptors, Interleukin-1; D051193:Toll-Like Receptors
keywords: Bivalve molluscs; Immune signalling; MyD88; TIR; Toll-like receptor