Potential Protease Inhibitor Isoforms from Pigeonpea against Helicoverpa armigera Gut Proteases

Ten pigeon pea genotypes (four moderately resistant, three intermediate, two moderately susceptible and one unknown status) were evaluated for their efficacy against bovine trypsin and Helicoverpa armigera (H. armigera) gut proteases. The trypsin inhibitor content in pigeon pea genotypes varied from 147.75 (TIU/g) (AL 201) to 177.85 TIU/g (AL 1495). Sodium dodecyl-polyacrylamide gel electrophoresis (SDS-PAGE) of seed extracts revealed different proteins of molecular weight ranging from 15.6 kDa to 98.5 kDa. Using gelatin SDS-PAGE, six different trypsin inhibitors with bovine trypsin were identified and four of them with relative mobility (R_m) 0.39, 0.78, 0.84 and 0.93 were present in all the ten genotypes. Five H. armigera protease inhibitors (PIs) were detected using the gelatin SDS-PAGE. Four of them also inhibited the bovine trypsin. One (35.3 kDa) was specific only for H. armigera gut proteases. Two protease inhibitors (15.6 kDa and 20.1 kDa) were specific for bovine trypsin. However, it appears that it is the unspecific PI with R_m 0.39 (51.5 kDa) and 0.93 (16.6 kDa) which mainly determine the resistance towards H. armigera in pigeonpea.