Insecticidal action of mammalian galectin-1 against diamondback moth (Plutella xylostella)

BACKGROUND: Previous studies showed that mammalian galectin-1 (GAL1) could interact with chitosan or chitin, one component of the peritrophic membrane (PM). This finding suggests that the PM could be a target of GAL1, which prompted the authors to explore the effect of GAL1 on larval growth and its potential mechanism. RESULTS: The development of Plutella xylostella (L.) larvae was significantly disturbed after they were fed recombinant GAL1. The histochemical structure and immunostaining pattern suggested that GAL1 treatment resulted in dose- and time- dependent disruption of the microvilli and abnormalities in these epithelial cells. Ultrastructural studies showed that the PM was not present in the midgut of GAL1-treated insects; instead, numerous bacteria were found in the lumen area. These results indicate that the protective function of the PM was disrupted by GAL1 treatment. Moreover, in vitro data showed that GAL1 interacts with chitosan/chitin in a dose-dependent manner, and also specifically binds to the PM in vitro. CONCLUSION: In view of the fact that the carbohydrate recognition domain of GAL1 recognises the structural motif N-acetyl lactosamine (Gal β 1-4 GlcNAc), which is similar to that of chitin (β-1,4 N-acetyl-D-glucosamine), it is proposed that the insecticidal mechanism of GAL1 involves direct binding with chitin to interfere with the structure of the PM.