摘要
Bitter gourd （Momordica charantia L.） seeds contain several squash-type serine proteinase inhibitors （PIs）, which inhibit the digestive proteinases of the polyphagous insect pest Helicoverpa armigera. In the present work isolation of a DNA sequence encoding the mature peptide of a trypsin inhibitor McTI-Ⅱ, its cloning and expression as a recombinant protein using Pichia pastoris have been reported. Recombinant McTI-Ⅱ inhibited bovine trypsin at 1 ： 1 molar ratio, as expected, but did not inhibit chymotrypsin or elastase. McTI-Ⅱ also strongly inhibited trypsin-like proteinases （81% inhibition） as well as the total proteolytic activity of digestive proteinases （70% inhibition） from the midgut of H. armigera larvae. The insect larvae fed with McTI-Ⅱ-incorporated artificial diet suffered over 70% reduction in the average larval weight after 12 days of feeding. Moreover, ingestion of McTI-Ⅱ resulted in 23% mortality in the larval population. The strong antimetabolic activity of McTI-Ⅱ toward H. armigera indicates its probable use in developing insect tolerance in susceptible plants.
Bitter gourd （Momordica charantia L.） seeds contain several squash-type serine proteinase inhibitors （PIs）, which inhibit the digestive proteinases of the polyphagous insect pest Helicoverpa armigera. In the present work isolation of a DNA sequence encoding the mature peptide of a trypsin inhibitor McTI-Ⅱ, its cloning and expression as a recombinant protein using Pichia pastoris have been reported. Recombinant McTI-Ⅱ inhibited bovine trypsin at 1 ： 1 molar ratio, as expected, but did not inhibit chymotrypsin or elastase. McTI-Ⅱ also strongly inhibited trypsin-like proteinases （81% inhibition） as well as the total proteolytic activity of digestive proteinases （70% inhibition） from the midgut of H. armigera larvae. The insect larvae fed with McTI-Ⅱ-incorporated artificial diet suffered over 70% reduction in the average larval weight after 12 days of feeding. Moreover, ingestion of McTI-Ⅱ resulted in 23% mortality in the larval population. The strong antimetabolic activity of McTI-Ⅱ toward H. armigera indicates its probable use in developing insect tolerance in susceptible plants.
