A mannose-specific lectin from the seeds of Canavalia rosea and its potential insecticidal activity against the stored product pest Callosobruchus maculatus

An attempt is made in the present investigation to test the efficacy of lectin purified from C. rosea against the major stored product insect pest, C. maculatus . Biochemical analysis carried out as the part of preliminary characterization revealed the presence of a mannose-specific lectin ( Cr MBL) from the crude seed kernel extract of C. rosea. The haemagglutinating (HA) activity of the extract was found to be divalent cation independent and EDTA insensitive. Further, the HA activity remained stable between pH 5 and 8 and unaffected between temperatures 10ºC and 70ºC. The lectin, Cr MBL from the crude seed kernel extracts of C. rosea was purified through single step affinity chromatography using the mannose-coupled epoxy activated Sepharose 6B. The purified lectin showed highest affinity to the simple carbohydrate, mannose. Various biochemical assays of the Cr MBL revealed a similar profile of results as observed in the preliminary characterization. Its molecular characterization using gel electrophoresis revealed five different polypeptide subunits viz ., 98 kDa, 80 kDa, 50 kDa, 30 kDa, and 15 kDa with a native mass of 273 kDa. Q-TOF-LC/MS of Cr MBL and MALDI-TOF-MS analysis of the 30 kDa polypeptide subunit of Cr MBL showed molecular similarity to several lectins, especially from Leguminosae family. The feeding bioassay with Cr MBL showed significant protection against the infestation of the stored product insect pest, C. maculatus . Lectin from C. virosa with more resistance to the activity of insect detoxifying enzymes could offer effective way of insect pest control with its suitability for employing this molecule as a component of integrated pest management.