A rapidly evolving secretome builds and patterns a sea shell

Abstract

Background: Instructions to fabricate mineralized structures with distinct nanoscale architectures, such as seashells and coral and vertebrate skeletons, are encoded in the genomes of a wide variety of animals. In mollusks, the mantle is responsible for the extracellular production of the shell, directing the ordered biomineralization of CaCO 3 and the deposition of architectural and color patterns. The evolutionary origins of the ability to synthesize calcified structures across various metazoan taxa remain obscure, with only a small number of protein families identified from molluskan shells. The recent sequencing of a wide range of metazoan genomes coupled with the analysis of gene expression in non-model animals has allowed us to investigate the evolution and process of biomineralization in gastropod mollusks.

Evolution of Nacre: Biochemistry and Proteomics of the Shell Organic Matrix of the Cephalopod Nautilus macromphalus

“…It does not take into consideration the "silent" secreted proteins, such as extrapallial fluid proteins, nor the proteins of the mantle epithelium, which may contribute to the shell elaboration without being constitutive of the shell matrix. [56] In spite of these technical limitations, it is puzzling to observe that most of the peptide sequences that we obtained do not exhibit any similarity with known molluskan shell proteins. This obviously points to the fundamental question of the diversity of molluskan shell proteins.…”

“…and the abalone Haliotis sp. Through investigation of new biological models on one hand, and through the use of new approaches on the other, such as "mantle transcriptomics" [56,57] and "shell proteomics" as here, the information on molluskan shell proteins increases at different levels: protein families, domains, and functions. Ultimately, it should allow more accurate definition of the basic "protein equipment" required for making a shell.…”

“…[13]) or the set of proteins determined by EST. [56] In the most consensual phylogenetic reconstructions of the phylum Mollusca, cephalopods and gastropods are grouped together in the Visceroconch (also called Cyrtosoma) clade, [58] which represents the sister group of diasomes (bivalves + scaphopods). The putative phylogenetic proximity of cephalopods and gastropods would be reflected in their respective nacre textures, which exhibit similarities, in contrast to bivalvian nacre.…”

Rapid evolution of pearl oyster shell matrix proteins with repetitive, low-complexity domains

“…The secretomes of P. maxima and the gastropod Haliotis asinina were compared, and although shematrin and KRMP genes were not found in H. asinina, this gastropod's mantle transcriptome contains other, seemingly unrelated, RLCDs. The lack of similarity between the Pinctada and Haliotis transcriptomes, and even between shematrin and KRMP genes in different species of pearl oyster, supports the proposition that many proteins in the molluscan mantle secretome are rapidly evolving [4].…”

Colour or no colour in the juvenile shell of the black lip pearl oyster, Pinctada margaritifera?

“…Among them, some are concerned with patterns (Ermentrout et al 1986), while others study the relationships between colour and genes (Atkinson and Warwick 1983;Adamkewicz and Castagna 1988;Peignon et al 1995;Rodrigues and Absalao 2005;Jackson et al 2006), or colour and diet (Reimchen 1979;Manriquez et al 2009). Genetics, diet and environment are described as factors influencing colour in a given species.…”