Evolution of the tyrosinase gene family in bivalve molluscs: independent expansion of the mantle gene repertoire.
Tyrosinase is a copper-containing enzyme that mediates the hydroxylation of monophenols and oxidation of o-diphenols to o-quinones. This enzyme is involved in a variety of biological processes, including pigment production, innate immunity, wound healing, and exoskeleton fabrication and hardening (e.g. arthropod skeleton and mollusc shell). Here we show that the tyrosinase gene family has undergone large expansions in pearl oysters (Pinctada spp.) and the Pacific oyster (Crassostrea gigas). Phylogenetic analysis reveals that pearl oysters possess at least four tyrosinase genes that are not present in the Pacific oyster. Likewise, C. gigas has multiple tyrosinase genes that are not orthologous to the Pinctada genes, indicating that this gene family has expanded independently in these bivalve lineages. Many of the tyrosinase genes in these bivalves are expressed at relatively high levels in the mantle, the organ responsible for shell fabrication. Detailed comparisons of tyrosinase gene expression in different regions of the mantle in two closely related pearl oysters, P. maxima and P. margaritifera, reveals that recently evolved orthologous tyrosinase genes can have markedly different expression profiles. The expansion of tyrosinase genes in these oysters and their co-option into the mantle's gene regulatory network is consistent with mollusc shell formation being underpinned by a rapidly evolving transcriptome.
Centre for Marine Sciences, School of Biological Sciences, The University of Queensland, Brisbane 4072, Australia.
Felipe
F
Aguilera
Centre for Marine Sciences, School of Biological Sciences, The University of Queensland, Brisbane 4072, Australia.
Carmel
C
McDougall
Centre for Marine Sciences, School of Biological Sciences, The University of Queensland, Brisbane 4072, Australia. Electronic address: b.degnan@uq.edu.au.
Bernard M
BM
Degnan
D060105:Animal Shells / Q000201:enzymology*; D000818:Animals; D049872:Bivalvia / Q000201:enzymology* / Q000235:genetics*; D019143:Evolution, Molecular; D015971:Gene Expression Regulation, Enzymologic; D008040:Genetic Linkage; D016678:Genome / Q000235:genetics; D014442:Monophenol Monooxygenase / Q000235:genetics*; D005810:Multigene Family; D010802:Phylogeny; D049911:Pinctada / Q000201:enzymology / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D026801:Synteny / Q000235:genetics; D059467:Transcriptome / Q000235:genetics
D012333:RNA, Messenger; D014442:Monophenol Monooxygenase
Bivalve; Gastropod; Mantle; Shell formation; Tyrosinase