Byssus Structure and Protein Composition in the Highly Invasive Fouling Mussel Limnoperna fortunei

Abstract

Biofouling mediated by byssus adhesion in invasive bivalves has become a global environmental problem in aquatic ecosystems, resulting in negative ecological and economic consequences. Previous studies suggested that mechanisms responsible for byssus adhesion largely vary among bivalves, but it is poorly understood in freshwater species. Understanding of byssus structure and protein composition is the prerequisite for revealing these mechanisms. Here, we used multiple methods, including scanning electron microscope, liquid chromatography–tandem mass spectrometry, transcriptome sequencing, real-time quantitative PCR, inductively coupled plasma mass spectrometry, to investigate structure, and protein composition of byssus in the highly invasive freshwater mussel Limnoperna fortunei. The results indicated that the structure characteristics of adhesive plaque, proximal and distal threads were conducive to byssus adhesion, contributing to the high biofouling capacity of this species. The 3,4-dihydroxyphenyl-α-alanine (Dopa) is a major post-transnationally modification in L. fortunei byssus. We identified 16 representative foot proteins with typical repetitive motifs and conserved domains by integrating transcriptomic and proteomic approaches. In these proteins, Lfbp-1, Lffp-2, and Lfbp-3 were specially located in foot tissue and highly expressed in the rapid byssus formation period, suggesting the involvement of these foot proteins in byssus production and adhesion. Multiple metal irons, including Ca2+, Mg2+, Zn2+, Al3+, and Fe3+, were abundant in both foot tissue and byssal thread. The heavy metals in these irons may be directly accumulated by L. fortunei from surrounding environments. Nevertheless, some metal ions (e.g., Ca2+) corresponded well with amino acid preferences of L. fortunei foot proteins, suggesting functional roles of these metal ions by interacting with foot proteins in byssus adhesion. Overall, this study provides structural and molecular bases of adhesive mechanisms of byssus in L. fortunei, and findings here are expected to develop strategies against biofouling by freshwater organisms.

Integrative Transcriptome and Proteome Analysis of the Tube Foot and Adhesive Secretions of the Sea Urchin Paracentrotus lividus

“…Mass spectrometry-based analyses have been frequently used in bioadhesion research [29,30,33,[49][50][51][52] to identify the proteins involved in adhesive processes. The species investigated in the bioadhesion field are generally non-model organisms and lack the benefits of broad, commonly available datasets, such as transcriptomes and genomes.…”

In Silico Analysis of Pacific Oyster (Crassostrea gigas) Transcriptome over Developmental Stages Reveals Candidate Genes for Larval Settlement

“…This sequence had 44.8% similarity ( E -value: 2.6 × 10 −57 ) to Byssal peroxidase-like protein 1 of Mytilus coruscus [34]. Byssal peroxidases have also been detected in the foot of Limnoperna fortunei [37] and byssus of Pinctada fucata [38]. The role of these enzymes remains uncertain, but byssal peroxidases could be involved in the protection of byssus from oxidizing environments and degradation brought about by microorganisms.…”

Identification of suitable reference genes for qPCR expression analysis on the gonads of the invasive mussel Limnoperna fortunei

“…To our knowledge, this is the first work that sought to validate RGs for the golden mussel in an effort to implement robust qPCR assays for gene expression analysis in this non-model organism. The application of qPCR to this species has been limited to the detection of larvae in the environment by absolute quantification, for which RGs are not required [38][39][40] and to one research article where qPCR was applied to evaluate gene expression in this mussel foot, but using a single non-validated RG [11]. We hope that the data presented here may help to change this picture, enabling the execution of reliable gene expression studies in the golden mussel gonads and contributing to advance the knowledge of the molecular mechanisms of key aspects of its extremely efficient reproduction, one of the distinguishing features of this aggressive invader.…”

“…An important milestone for understanding the biology of this species was the sequencing of its genome [9]. In addition, transcriptomic (RNA-seq) analyses have been performed for tissues such as the digestive glands, foot, mantle, muscle [9,10,11], and, more recently, for tissue from the gonads of both sexes [12]. This latest work characterized the gene expression profile of adult male and female gonads and revealed almost 4000 sex-biased transcripts in this tissue.…”