Biochemical characterization of alkaline phosphatase in midgut of Cry2Ab dosed, pink bollworm, Pectinophora gossypiella (Saunders)

Abstract

Aim: The holistic management of pink bollworm is possible only after uncovering the underlying mechanism/s of pink bollworm resistance. The present study was carried out for investigating the effect of Cry2Ab toxin on alkaline phosphatase activity and expression of its isoforms in midgut of Pectinophora gossypiella. Methodology: Resistant and susceptible pink bollworm larval populations were subjected to Cry2Ab bioassays using F1 larvae in a 21 days diet-incorporation method. The total midgut protein was estimated by Bradford method. Alkaline phosphatase activity was estimated in midgut homogenates, Non-denaturing SDS-PAGE and Native polyacrylamide gel electrophoresis was performed by the following standard procedures. Results: The study showed increased alkaline phosphatase activity in pink bollworm midgut is correlated with insect resistance in response to Cry2Ab. The non-denaturing SDS-PAGE analysis of pink bollworm midgut alkaline phosphatase isozymes had differential banding patterns in resistant and susceptible populations. Yavatmal (R1), Hingoli (R4) and Parbhani (R5) showed similar banding patterns ranging from 65-95 kDa; Guntur (R2) and Hingoli (R3) showed near similar banding patterns ranging from 70-95 kDa; whereas susceptible population showed banding pattern in the range of 50-70 kDa. Interpretation: The expression profiles of alkaline phosphatase isomers in resistant and susceptible populations can be utilized as a biomarker to aid for the screening of PBW infected Bt -cotton fields and development of pink bollworm management strategies. Key words: Alkaline Phosphatase, Cry2Ab, Insect resistance, Pectinophora gossypiella, SDS-PAGE