Wound and methyl jasmonate induced pigeon pea defensive proteinase inhibitor has potency to inhibit insect digestive proteinases.

Wounding of plants by chewing insects or other damage induces the synthesis of defensive proteinase inhibitors (PI) in both wounded and distal unwounded leaves. In the present paper we report the characterization of inducible defensive PI from pigeon pea (Cajanus cajan) and its in vitro interaction with Helicoverpa armigera gut proteinases (HGP). We found that PI activity was induced in local as well as systemic leaves of pigeon pea by the wounding and methyl jasmonate (MeJA) application. Consistent induction of PI was observed in two wild cultivars of pigeon pea at various growth stages. The estimated molecular weight of inducible PI was ~16.5 kDa. Electrophoretic analysis and enzyme assays revealed that the induced PI significantly inhibited total gut proteinase as well as trypsin-like activity from the midgut of H. armigera. The induced PI was found to be inhibitor of trypsin as well as chymotrypsin. Study could be important to know the further roles of defensive PIs.