CHICKPEA DEFENSIVE PROTEINASE-INHIBITORS CAN BE INACTIVATED BY PODBORER GUT PROTEINASES

Developing chickpea (Cicer arietinum L.) seeds 12 to 60 d after flower ing (DAF) were analyzed for proteinase inhibitor (Pi) activity. In add ition, the electrophoretic profiles of trypsin inhibitor (Ti) accumula tion were determined using a gel-radiographic film-contact print metho d. There was a progressive increase in Pi activity throughout seed dev elopment, whereas the synthesis of other proteins was low from 12 to 3 6 DAF and increased from 36 to 60 DAF. Seven different Ti bands were p resent in seeds at 36 DAF, the time of maximum podborer (Helicoverpa a rmigera) attack. Chickpea Pis showed differential inhibitory activity against trypsin, chymotrypsin, H. armigera gut proteinases, and bacter ial proteinase(s). In vitro proteolysis of chickpea Ti-l with various proteinases generated Ti-5 as the major fragment, whereas Ti-6 and -7 were not produced. The amount of Pi activity increased severalfold whe n seeds were injured by H. armigera feeding. In vitro and in vivo prot eolysis of the early- and late-stage-specific Tis indicated that the c hickpea Pis were prone to proteolytic digestion by H. armigera gut pro teinases. These data suggest that survival of H. armigera on chickpea may result from the production of inhibitor-insensitive proteinases an d by secretion of proteinases that digest chickpea Pis.