Functional Characterization of a Galectin Gene NlGalectin-8 Involved in Development and Antifungal Immunity in the Rice Pest Nilaparvata lugens

Galectins are an evolutionarily conserved family of carbohydrate-binding proteins involved in pathogen defense and therefore hold promise for developing entomopathogen-based pest control. However, the immunological roles and biocontrol potential of galectins from Nilaparvata lugens (brown planthopper, BPH), a highly destructive rice pest, remain poorly understood. Here, a galectin-encoding gene NlGalectin-8 was identified and functionally characterized in BPH. NlGalectin-8 was expressed ubiquitously throughout all tested developmental stages and tissues, with relatively high expression in the stages of egg and early-instar nymphs and tissues of hemolymph and fat bodies. The expression of NlGalectin-8 was strongly induced by infection with an entomopathogenic fungus (EPF) Metarhizium anisopliae. RNA interference (RNAi)-mediated silencing of NlGalectin-8 significantly reduced adult survival and fecundity. Downregulation of NlGalectin-8 also markedly augmented susceptibility to EPF infection, which might be attributable to the weakened antifungal immunity and alteration of bacterial symbiont abundance. Our findings advance understanding of antifungal immunity in BPH and provide insights for developing EPF-based strategies for BPH control.