Myticalins: A Novel Multigenic Family of Linear, Cationic Antimicrobial Peptides from Marine Mussels (Mytilus spp.)

Abstract

The application of high-throughput sequencing technologies to non-model organisms has brought new opportunities for the identification of bioactive peptides from genomes and transcriptomes. From this point of view, marine invertebrates represent a potentially rich, yet largely unexplored resource for de novo discovery due to their adaptation to diverse challenging habitats. Bioinformatics analyses of available genomic and transcriptomic data allowed us to identify myticalins, a novel family of antimicrobial peptides (AMPs) from the mussel Mytilus galloprovincialis, and a similar family of AMPs from Modiolus spp., named modiocalins. Their coding sequence encompasses two conserved N-terminal (signal peptide) and C-terminal (propeptide) regions and a hypervariable central cationic region corresponding to the mature peptide. Myticalins are taxonomically restricted to Mytiloida and they can be classified into four subfamilies. These AMPs are subject to considerable interindividual sequence variability and possibly to presence/absence variation. Functional assays performed on selected members of this family indicate a remarkable tissue-specific expression (in gills) and broad spectrum of activity against both Gram-positive and Gram-negative bacteria. Overall, we present the first linear AMPs ever described in marine mussels and confirm the great potential of bioinformatics tools for the de novo discovery of bioactive peptides in non-model organisms.

Massive gene presence/absence variation in the mussel genome as an adaptive strategy: first evidence of a pan-genome in Metazoa

“…For example, each individual only possesses, on average, nine out of the 63 myticin variants identified (Figure 4B, Supplementary Data Note 18). In light of this observation, PAV emerges as the main factor in determining the high intraspecific sequence diversity observed both at the mRNA and protein level in mussel AMPs (39,40). On the other hand, other gene families were significantly under-represented among dispensable genes.…”

“…In spite of the growing number of reports of pan-genomes in eukaryotes and the recent extension of such investigations to human populations (32), so far the impact of PAV on the intraspecific diversity of animals has been presumed to be minimal, and sometimes linked to the development of pathologies (38). To the best of our knowledge, PAV has been only marginally explored in bivalves as a phenomenon linked to gene families involved in immune functions, i.e., big defensins in Crassostrea gigas (39) and myticalins in M. galloprovincialis (40). Therefore, this is the first study to report the widespread occurrence of PAV at a whole genome scale in metazoans, and the very first report of a pan-genome in the animal kingdom.…”

Fragments of the Nonlytic Proline-Rich Antimicrobial Peptide Bac5 Kill Escherichia coli Cells by Inhibiting Protein Synthesis

“…The in vitro translation reactions were performed with a final volume of 25 l (containing 240 mM HEPES [pH 8], 0.6 mM polyethylene glycol 8000, 60 mM glucose, 4.4 g bulk tRNA from E. coli MRE600 [Sigma], 1.2 mM ATP, 1.2 mM GTP, 0.85 g folinic acid, 1 mM DTT, 90 mM potassium glutamate. 80 mM ammonium acetate, 20 mM K 2 HPO 4 , 1.8 mM each amino acid, 12.6 mM magnesium acetate, and 200 ng of firefly luciferase mRNA synthesized in vitro as reported previously [48]) using 6.75 l of bacterial lysate and 1 l of peptide solution where required. The reaction mixtures were incubated at 30°C for 1 h under agitation (550 rpm).…”

Antibacterial and Antibiofilm Activity of Temporin-GHc and Temporin-GHd Against Cariogenic Bacteria, Streptococcus mutans

“…The two-fold dilution method was used to determine the minimum inhibitory concentration (MIC) of the peptides as described previously (Leoni et al, 2017). S. mutans in the exponential phase was diluted to 2 × 10 6 CFU/ml in BHI.…”