First Insights into the Repertoire of Secretory Lectins in Rotifers

Abstract

Due to their high biodiversity and adaptation to a mutable and challenging environment, aquatic lophotrochozoan animals are regarded as a virtually unlimited source of bioactive molecules. Among these, lectins, i.e., proteins with remarkable carbohydrate-recognition properties involved in immunity, reproduction, self/nonself recognition and several other biological processes, are particularly attractive targets for biotechnological research. To date, lectin research in the Lophotrochozoa has been restricted to the most widespread phyla, which are the usual targets of comparative immunology studies, such as Mollusca and Annelida. Here we provide the first overview of the repertoire of the secretory lectin-like molecules encoded by the genomes of six target rotifer species: Brachionus calyciflorus, Brachionus plicatilis, Proales similis (class Monogononta), Adineta ricciae, Didymodactylos carnosus and Rotaria sordida (class Bdelloidea). Overall, while rotifer secretory lectins display a high molecular diversity and belong to nine different structural classes, their total number is significantly lower than for other groups of lophotrochozoans, with no evidence of lineage-specific expansion events. Considering the high evolutionary divergence between rotifers and the other major sister phyla, their widespread distribution in aquatic environments and the ease of their collection and rearing in laboratory conditions, these organisms may represent interesting targets for glycobiological studies, which may allow the identification of novel carbohydrate-binding proteins with peculiar biological properties.

Taxonomic Distribution and Molecular Evolution of Mytilectins

“…These lectins are characterized by a CRD that displays a unique β-trefoil structural organization, consisting of three homologous subdomains, which most likely derive from the duplication of an ancestral smaller glycan-binding peptide [12]. Although this CRD is often found associated with other domains in large proteins that carry out functions linked with carbohydrate biosynthesis and metabolism [13], several RTLs displaying a simple architecture, which only include a single CRD, have been previously described in a few phyla of invertebrate animals [14][15][16][17]. Among these, a group of sequences that display a highly divergent primary sequence from all other previously described RTLs have attracted significant attention due to their glycan-binding specificity, which could make them interesting targets for biotechnological applications.…”

Invertebrate C1q Domain-Containing Proteins: Molecular Structure, Functional Properties and Biomedical Potential

“…One such group was the C1q domain-containing proteins, which are abundant in various invertebrates. C1qDC proteins and their genes and transcripts have been found in cnidarians, echinoderms, hemichordates, tunicats, nemerteans, annelids, rotifers, brachiopods, mollusks, and arthropods [21][22][23][24][25][26]. A particularly large number of C1qDC genes were found in the genomes of bivalves: 98 in Crassostrea hongkongensis (Magallana hongkongensis) [27], 296 in Pinctada fucata [28], 337 in Crassostrea gigas (Magallana gigas) [29], 408 in Mercenaria mercenaria [30], 445 in Modiolus philippinarum [31], 524 in Mytilus edulis [32], 554 in Saccostrea glomerata [33], 476 in Crassostrea virginica [34], 1182 in Ruditapes philippinarum [35], and more than 150 as transcripts in hemocytes of Mytilus galloprovincialis [36,37].…”

New l-Rhamnose-Binding Lectin from the Bivalve Glycymeris yessoensis: Purification, Partial Structural Characterization and Antibacterial Activity

“…Most likely, bivalves have developed mechanisms to avoid excessive immune reactions and to exert strong control of their inflammatory responses [6]. Invertebrate lectins are characterized by different structures, size, molecular organization, carbohydrate specificity and classified into galectins, C-type lectins, fucolectins, pentraxins and rhamnose-binding lectins (RBLs) [7,8].…”