A brief history of galectin evolution.

Area of Science:

• Evolutionary Biology
• Biochemistry
• Genomics

Background:

• Galectins are abundant, diverse carbohydrate-binding proteins in vertebrates with varied functions.
• Related proteins exist in primitive Bilateria, suggesting ancient origins.
• Previous research lacked a comprehensive phylogenetic history of the galectin family.

Purpose of the Study:

• To reconstruct the phylogenetic history of the galectin family within Bilateria.
• To hypothesize the origin and diversification of galectins in jawed vertebrates (Gnathostomata).
• To investigate the evolutionary significance of Cyclostomata galectins and galectin-related protein 2.

Main Methods:

• Comparative genomics and synteny analyses across bilaterian genomes.
• Phylogenetic reconstruction of galectin gene evolution.
• Identification and characterization of galectin paralogs and ohnologues.

Main Results:

• The putative ancestral Bilateria galectin is traced to scallops, representing a slow-evolving lineage.
• The primordial Deuterostomata galectin likely possessed galectin-8-like tandem-repeat structure and sialic acid binding.
• The study reconstructs the amplification of this ancestral galectin to modern vertebrate galectins, distinguishing duplication events.
• Galectin-related protein 2 is identified as a widespread ohnologue of the ancestral tandem-repeat galectin in Gnathostomata.

Conclusions:

• A novel hypothesis for the origin and diversification of vertebrate galectins is proposed.
• The evolutionary relationships among Gnathostomata galectins are clarified.
• The study provides insights into the evolutionary history of Cyclostomata and highlights the neglected galectin-related protein 2.