Characterization and functional analysis of Spodoptera litura galectins

Insects rely on their effective innate immune system to defend against pathogen infection, and pattern recognition receptors (PRRs) play a crucial role in insect immunity. Galectins, a family of animal β-galactoside-binding lectins, may serve as PRRs. Mammalian galectins are involved in diverse physiological processes; however, less is known about functions of insect galectins.

In this study, we focused on an agricultural pest Spodoptera litura and identified a total of 13 Slgalectins, and a functional study of Slgalectin-4 and Slgalectin-7 was conducted. Both recombinant Slgalectin-4 and Slgalectin-7 proteins directly bound to Bacillus thuringiensis and an entomopathogenic fungus Metarhizium rileyi. Importantly, supplementing recombinant Slgalectin-4 to S. litura larvae significantly increased larval survival after M. rileyi infection but accelerated larvae death after B. thuringiensis infection, whereas supplementing Slgalectin-7 increased larval survival after B. thuringiensis infection but did not influence larval survival after M. rileyi infection. Supplementing both Slgalectin-4 and Slgalectin-7 altered the expression of some antimicrobial peptide genes in larval hemocytes after microbial infection, which may partly account for the roles of Slgalectin-4 and -7 in larval survival.

Our findings revealed that Slgalectin-4 and -7 may serve as PRRs to bind different pathogens and alter expression of immune effector genes such as antimicrobial peptide genes, eventually modulating immune responses of S. litura larvae to pathogens such as B. thuringiensis and M. rileyi. © 2025 Society of Chemical Industry.