Identification of a laccase gene involved in shell periostracal tanning of the clam Meretrix petechialis

Abstract

Tanning is a complex extracellular process that is a mechanism for stabilizing proteinaceous extracellular structures. Phenoloxidases play important roles in cross-linking during tanning, and laccase (EC 1.10.3.2) is a member of the phenoloxidase enzyme class. In this study, we identified a laccase gene (MpLac) from the clam Meretrix petechialis and found that MpLac might be involved in shell periostracal tanning of clams. Using whole-mount in situ hybridization, we found that MpLac mRNA in the larval clam was mainly expressed in the mantle edge. In the adult clam, our quantitative real-time PCR results showed that the mantle was also a tissue with a high MpLac expression level; in addition, by combining the results of fluorescence in situ hybridization, H&E staining and transmission electron microscopy, we found that the inner epithelium of the outer fold of the mantle edge, which is involved in periostracum formation, was the exact region in which MpLac mRNA was expressed. Furthermore, knocking down the expression of MpLac by RNA interference (RNAi) bleached the new shell periostracum. All of our results suggest the involvement of MpLac in shell periostracal tanning of M. petechialis.

The shell matrix of the european thorny oyster, Spondylus gaederopus: microstructural and molecular characterization

“…The two enzymes identified also have functions related to shell formation: i) chitinase, a chitin binding protein that catalyses the cleavage of chitin, could be involved in the (re)modeling of the chitinous scaffold (Yonezawa et al, 2016); ii) laccase [Mizuhopecten yeonessis], a copper oxidase enzyme, could be involved in cross-linking of the matrix during biomineralization. In the prism matrix of the pearl oyster, an enzyme with similar function was identified , while laccase-like genes have been shown to be involved in shell immunity, biomineralization and pigmentation (Mao et al, 2018;Yue et al, 2019). We note that all of the six identified shell matrix proteins are intrinsically disordered (Fig.…”

Transcriptome analysis reveals core lncRNA-mRNA networks regulating melanization and biomineralization in Patinopecten yessoensis shell-infested by Polydora

“…Herein, a perlucin also displayed an obviously higher expression level in Polydora -infected P. yessoensis , and it was potentially targeted by 23 DELs (e.g., TCONS_00116040, TCONS_00046855, TCONS_00062896, etc.). Laccase, another phenoloxidases, has been shown participating in shell immunity, pigmentation and biomineralization [ 8 , 92 , 93 ]. During biomineralization, laccase could direct the cross-linking of shell matrix [ 93 , 94 ].…”

The degradation of intracrystalline mollusc shell proteins: A proteomics study of Spondylus gaederopus

“…The analysis of Spondylus shell samples by LC-MS/MS allowed us to identify five proteins, all belonging to the pectinoid mollusc shell Pecten maximus. These include: 1) protein LOC117318053 which is characterised by the presence of four von Willebrand factor A domains (vWA), a chitin binding domain (CBD), intrinsically disordered region (IDR) and is homologous to other shell matrix proteins [92]; 2) carbonic anhydrase, which is an enzyme that is involved in catalysing the conversion of carbon dioxide and water into carbonic acid, protons and bicarbonate ions and which is ubiquitous in mollusc shell matrices [93]; 3) laccase-2-like enzyme, which displays copper ion binding and oxidoreductase activity and belongs to the cupredoxin superfamily, although its role in biomineralisation is poorly understood [94,95]; 4) aquaporin-like, a water channel protein that is involved in transmembrane transport processes facilitating water diffusion, albeit its role in shell biomineralisation is also not well known [96] and 5) mucin-like, a gel-forming protein; mucins are typically characterised by high molecular weight, are heavily glycosylated (up to 70-80% of their structure) with tandem repeat units [97] and they have also been identified in other matrices from molluscan shells [98,99]. However, among these sequences, only the uncharacterised protein LOC117318053 had reasonably extensive coverage (it was supported by 25 unique peptides) and this was further used to study peptide bond hydrolysis patterns.…”