Helicoverpa armigera is an orthodox rival of many crop plants affecting agricultural economy. Plant leaves found to accumulate proteinase inhibitors, although this insect pest chooses leaves for laying eggs. Plant defense response at this juncture is not fully explored. In this context, here we are reporting proteinase inhibitor (ppLPI-1) having significant homology with the I13 family from leaves of pigeonpea (cv. BSMR 736). The isolation of ppLPI-1 was carried out from leaves of field-grown pigeonpea under an outbreak of H. armigera. The acetone precipitated ppLPI-1 (125 µg) displayed substantial inhibition potential towards bovine trypsin (56.5 ± 1.8%) and HaGPs (52.6 ± 1.7%) on solution assay. These results were corroborated with dot-blot analysis. The molecular form of ppLPI-1 was characterized by reverse zymography and GXCP. The optimum condition was found to be pH 8 and temperature in the range of 30-40 °C. The protein identification via MASCOT-PMF and NCBI-BLAST search showed substantial homology with an inducible subtilisin inhibitor of Fabaceae comprising Vigna angularis (96%), Canavalia lineata (78%), Cicer arietinum (76%), Glycine max (75%), Medicago truncatula (73%) and Vicia faba (73%) consists of conserved domain of potato inhibitor I family.
Keywords: HaGPs; Helicoverpa armigera; Pigeonpea; Proteinase inhibitor; Subtilisin inhibitor; ppLPI-1.