Understanding Snail Mucus Biosynthesis and Shell Biomineralisation through Genomic Data Mining of the Reconstructed Carbohydrate and Glycan Metabolic Pathways of the Giant African Snail (Achatina fulica)

Abstract

The giant African snail (Order Stylommatophora: Family Achatinidae), Achatina fulica (Bowdich, 1822), is the most significant and invasive land snail pest. The ecological adaptability of this snail involves high growth rate, reproductive capacity, and shell and mucus production, driven by several biochemical processes and metabolism. The available genomic information for A. fulica provides excellent opportunities to hinder the underlying processes of adaptation, mainly carbohydrate and glycan metabolic pathways toward the shell and mucus formation. The authors analysed the 1.78 Gb draft genomic contigs of A. fulica to identify enzyme-coding genes and reconstruct biochemical pathways related to the carbohydrate and glycan metabolism using a designed bioinformatic workflow. Three hundred and seventy-seven enzymes involved in the carbohydrate and glycan metabolic pathways were identified based on the KEGG pathway reference in combination with protein sequence comparison, structural analysis, and manual curation. Fourteen complete pathways of carbohydrate metabolism and seven complete pathways of glycan metabolism supported the nutrient acquisition and production of the mucus proteoglycans. Increased copy numbers of amylases, cellulases, and chitinases highlighted the snail advantage in food consumption and fast growth rate. The ascorbate biosynthesis pathway identified from the carbohydrate metabolic pathways of A. fulica was involved in the shell biomineralisation process in association with the collagen protein network, carbonic anhydrases, tyrosinases, and several ion transporters. Thus, our bioinformatic workflow was able to reconstruct carbohydrate metabolism, mucus biosynthesis, and shell biomineralisation pathways from the A. fulica genome and transcriptome data. These findings could reveal several evolutionary advantages of the A. fulica snail, and will benefit the discovery of valuable enzymes for industrial and medical applications.

Gastropod Mucus: Interdisciplinary Perspectives on Biological Activities, Applications, and Strategic Priorities

“…However, structure–function relationships are limited. For instance, antimicrobial protection is attributed to lectins, enzymes, and cationic peptides, , but their relative contributions are unclear. Lubrication is proposed to involve proteoglycan hydration and fluid gel transitions, but the molecular basis is unknown.…”

“…Polysaccharide components include sulfated glycosaminoglycans like chondroitin sulfate. Smaller peptides and hydrophobic lipids are also present within the mucin network. ,, Variations in mucus biochemical properties such as lectin content, metal ions, and aromatic amino acids correlate with specialized adhesive functions adapted to diverse environments. Ions, oxidation cross-links, and lectin-carbohydrate interactions contribute to mucus gel stiffness and adhesion. ,, This composition allows mucus to exhibit properties such as reversible gelation, high viscosity, and self-healing (Figure ).…”

“…In A. vulgaris , numerous mucus-associated proteins, including many secreted C-type lectins, were identified . Genomic analysis of Achatina fulica reconstructed metabolic pathways involved in mucus formation, providing insights into its biochemical origins . The authors identified enzymes for glycosaminoglycan biosynthesis, including those producing keratan sulfate, heparan sulfate, acharan sulfate, and chondroitin sulfate found in the mucus.…”

“…For instance, antimicrobial protection is attributed to lectins, enzymes, and cationic peptides, , but their relative contributions are unclear. Lubrication is proposed to involve proteoglycan hydration and fluid gel transitions, but the molecular basis is unknown. The variation in mucus composition and rheology across species is not understood.…”

De novo genome assembly and transcriptome sequencing in foot and mantle tissues of Megaustenia siamensis reveals components of adhesive substances

“…Consequently, there is a growing interest in exploring terrestrial gastropod mucus for medical, pharmaceutical, and cosmetic applications 5 – 8 . Studies have examined its protein components, glycosylation, ion content, and mechanical properties 2 , 4 , and advancements in genomic and transcriptomic data enable the reconstruction of snail mucus biosynthetic pathways 9 . However, most studies into the genomic structure and differential gene expression of terrestrial gastropods have focused predominantly on snails and slugs 10 – 12 , neglecting semislugs entirely.…”