Genomics and transcriptomics of the green mussel explain the durability of its byssus

Koji Inoue,Yuki Yoshioka,Mieko Sassa,Takehiko Itoh,Ikuo Ueda,Atsushi Toyoda,Hiroyuki Tanaka,Chuya Shinzato,Azusa Kinjo

doi:10.1038/s41598-021-84948-6

Abstract

Mussels, which occupy important positions in marine ecosystems, attach tightly to underwater substrates using a proteinaceous holdfast known as the byssus, which is tough, durable, and resistant to enzymatic degradation. Although various byssal proteins have been identified, the mechanisms by which it achieves such durability are unknown. Here we report comprehensive identification of genes involved in byssus formation through whole-genome and foot-specific transcriptomic analyses of the green mussel, Perna viridis. Interestingly, proteins encoded by highly expressed genes include proteinase inhibitors and defense proteins, including lysozyme and lectins, in addition to structural proteins and protein modification enzymes that probably catalyze polymerization and insolubilization. This assemblage of structural and protective molecules constitutes a multi-pronged strategy to render the byssus highly resistant to environmental insults.

Highlights

Mussels, which occupy important positions in marine ecosystems, attach tightly to underwater substrates using a proteinaceous holdfast known as the byssus, which is tough, durable, and resistant to enzymatic degradation
The green mussel is relatively tolerant of anthropogenic chemical pollutants, concentrating them in the body[11]
As the list included various proteinase inhibitors, defense proteins, and lectins, in addition to structural proteins, such as fps and collagens and their processing enzymes, we propose that byssus formation includes construction of resilient structures, and genes for protection of the byssus

Summary

Introduction

Mussels, which occupy important positions in marine ecosystems, attach tightly to underwater substrates using a proteinaceous holdfast known as the byssus, which is tough, durable, and resistant to enzymatic degradation. Six major types of fps (fp-1 to -6) have been discovered and each contains post-translationally modified amino acid residues such as Dopa (3,4-dihydroxyphenylalanine), hydroxyproline, hydroxyarginine, and phosphoserine[2,6] Such amino acid modifications, especially the crosslinking of Dopa residues, are thought to be involved in polymerization and insolubilization of fps, detailed functions have yet to be c onfirmed[2]. Expansion of these analyses to other mussel species suggest that byssus formation mechanisms are unexpectedly diverse among species. We performed whole genome sequencing of the green mussel, P. viridis (Fig. 1) to understand physiological systems comprehensively, including byssus formation. Whole genome sequencing of this species is expected to contribute to understanding of its ecology, physiology, and the ecosystems it inhabits

Methods

Results

Conclusion