Recombinant lectin from the coastal jack bean Canavalia rosea and its anti-bruchid activity towards Callosobruchus maculatus (Chrysomelidae: Coleoptera)

Abstract

The insect Callosobruchus maculatus is a potential pest of stored products responsible for damage to legume crops by infesting their seeds, resulting in substantial impairment to their nutritional composition. A few leguminous seeds containing lectins have been found to have the most adverse effects, with the potential to hinder the metabolism of seed-feeding insects. In the present investigation, a lectin gene from the beach bean, Canavalia rosea, was. isolated and its open reading frame encoding 290 amino acids was cloned into pET-45b (+), transformed using BL21 (DE3) cells, and the expressed 30 kDa recombinant lectin polypeptide (CrLP) was purified and characterized. Artificial seeds containing 0.1%, 0.5% and 1.0% concentrations of CrLP were tested for their protective role against the infestation of C. maculatus, wherein a significant reduction in seed damage and adult emergence was observed. Larvae of C. maculatus fed on artificial seeds containing CrLP were evaluated for the enzymes involved in the detoxification processes using RT-qPCR. The expression analysis of various insect detoxification enzymes revealed a significant downregulation of cytochrome p450, glutathione S-transferase, and esterase in larvae raised on all three tested concentrations of CrLP. This study thus demonstrates the potential insecticidal nature of recombinant lectin polypeptide derived from the seeds of C. rosea towards the insect pest C. maculatus.