Genetic engineering with α-amylase inhibitors makes seeds resistant to bruchids

Seeds of the common bean, Phaseolus vulgaris, contain two inhibitors of mammalian and insect alpha-amylases (alpha Als) that show specificity towards the amylases of different insect species. Expression in pea (Pisum sativum) and azuki bean (Vigna angularis) of a chimeric gene consisting of the cDNA of bean alpha Al-1 and a seed-specific promoter makes the seeds of these legumes resistant to three species of Old World bruchids whose amylases are inhibited by alpha Al-1. This was the first successful genetic engineering of insect resistance in seeds. To understand the basis of the specificity between amylases and inhibitors we cloned a second bean inhibitor (alpha Al-2) with different specificity, and we cloned the cDNA of the New World bruchid, Zabrotes subfasciatus. The amylase of this bruchid is inhibited by alpha Al-2, but not by alpha Al-1. Knowledge of the amino acid sequences and of the three-dimensional structure of the pancreatic alpha-amylase-alpha Al-1 complex allows us to predict the peptide domains and amino acids of the proteins that are important for protein-protein recognition and inhibition of enzyme activity.