PROTEINASE-INHIBITORS FROM NICOTIANA-ALATA ENHANCE PLANT-RESISTANCE TO INSECT PESTS

The ornamental tobacco (Nicotiana alata) produces one 6-kDa chymotryps in inhibitor and four 6-kDa trypsin inhibitors from a single 40.3-kDa precursor protein. Three different approaches have been used to assess the potential of these proteinase inhibitors (PIs) in insect control. The first was an in-vitro approach in which all five inhibitors, the single chymotrypsin inhibitor or three of the four trypsin inhibitors were tested for their ability to inhibit gut protease activity in inse cts from four orders. The second approach was to incorporate the N. al ara PIs in the artificial diet of the native budworm (Helicoverpa punc tigera) and the black field cricket (Teleogryllus commodus). H. puncti gera larvae and T. commodus nymphs had a significant (P < 0.01) reduct ion in growth after ingestion of the PI and were more lethargic than i nsects on the control diet, Several of the H. punctigera larvae also f ailed to complete moulting at the third or fourth instar. The third ap proach was to express the N. alata PIs in transgenic tobacco under the control of the 35S CaMV promoter, When H. punctigera a larvae were fe d tobacco leaves expressing the N. alata PIs at 0.2% soluble protein, significant (P < 0.01) differences in mortality and/or growth rate wer e observed. (C) 1997 Elsevier Science Ltd.