Chickpea Defensive Proteinase Inhibitors Can Be Inactivated by Podborer Gut Proteinases1

Abstract

Developing chickpea (Cicer arietinum L.) seeds 12 to 60 d after flowering (DAF) were analyzed for proteinase inhibitor (Pi) activity. In addition, the electrophoretic profiles of trypsin inhibitor (Ti) accumulation were determined using a gel-radiographic filmcontact print method. There was a progressive increase in Pi activity throughout seed development, whereas the synthesis of other proteins was low from 12 to 36 DAF and increased from 36 to 60 DAF. Seven different Ti bands were present in seeds at 36 DAF, the time of maximum podborer (Helicoverpa armigera) attack. Chickpea Pis showed differential inhibitory activity against trypsin, chymotrypsin, H. armigera gut proteinases, and bacterial proteinase(s). In vitro proteolysis of chickpea Ti-1 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 when seeds were injured by H. armigera feeding. In vitro and in vivo proteolysis of the earlyand late-stage-specific Tis indicated that the chickpea Pis were prone to proteolytic digestion by H. armigera gut proteinases. These data suggest that survival of H. armigera on chickpea may result from the production of inhibitor-insensitive proteinases and by secretion of proteinases that digest chickpea Pis.In a co-evolving system of plant-insect interactions, plants synthesize a variety of toxic proteinaceous and nonproteinaceous molecules for their protection against insects

Digestive enzymes during development of Ceratitis capitata (Diptera:Tephritidae) and effects of SBTI on its digestive serine proteinase targets

“…However, when SBTI was incorporated into artificial diets and offered to C. capitata larvae at WD 50 of 3.01% was observed, with a slight effect on larval mortality, in disagreement with the results obtained in vitro. This probably happens because insect pests adapt to host plant proteinase inhibitors by synthesizing proteinases that are either insensitive to inhibitors (Jongsma et al, 1995;Broadway, 1997) or have the capacity to degrade them (Michaud, 1997;Giri et al, 1998). Zymogram using SBTI showed interactions between enzyme and inhibitor, with complex retardation during electrophoresis.…”

Inhibition of cysteine and aspartyl proteinases in the alfalfa weevil midgut with biochemical and plant-derived proteinase inhibitors

“…The necessity of such a strategy has become increasingly evident with the understanding that many insects possess very effective resistance mechanisms against individual PIs. Resistance has been attributed to complex proteolytic systems, allowing the insects to degrade PIs in Coleoptera (Girard et al, 1998a) and Lepidoptera (Giri et al, 1998), and to enhance the production of inhibitor-insensitive proteinases in response to PI ingestion in Coleoptera (Girard et al, 1998b;Bonade-Bottino et al, 1999;Cloutier et al, 1999) and Lepidoptera (Broadway 1995(Broadway , 1997Jongsma et al, 1995;Broadway, 1996b;Brown et al, 1997;Wu et al, 1997). It has been suggested (Orr et al, 1994;Broadway, 1996a) that such complex mechanisms are most likely to exist in polyphagous insects having generalized feeding habits compared to oligo-or monophagous insects.…”

Purification and characterization of trypsin inhibitor from Cicer arietinum L. and its efficacy against Helicoverpa armigera

“…Therefore, it is important to biochemically characterize the protease inhibitors from various indigenous cultivated legumes and evaluate their insecticidal potential Chickpea, the world's third most important pulse crop (FAO Production Yearbook, 1993), suffers severe losses due to insect predation. Most of these losses are caused by the podborer Helicoverpa armigera, a polyphagous pest of the developing seeds of several legume species (Giri et al, 1998). For this reason, it became important to assess the levels of protease inhibitors from chickpea and their interaction with the gut protease of H. armigera.…”