Barley trypsin inhibitor CMe confers insect resistance to wheat

Abstract

Proteinase inhibitors have been proposed to be involved in the defence response against herbivorous pests (Hoffmann et al. 1992). The efficacy of a specific inhibitor depends on the structural compatibility of its reactive site with the substrate-binding site of the targeted proteinase. For example, trypsin-inhibitors include either an arginyl or lysyl residue, which is recognized by trypsin-like enzymes. Barley trypsin inhibitor CMe (BTI-CMe), an abundant protein in barley endosperm, is one of the best characterized members of the cereal multigene family of trypsin/a-amylase inhibitors (Carbonero and Gracia-Olmedo, 1998) and was first purified from barley flour as a protein of 14 KDa that was specifically active in vitro against trypsin. Recently BTI-CMe was shown to inhibit specifically the trypsin-like proteases of the gut extracts of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) (Alfonso et al. 1997), whereas the BTICMe inhibitor is rapidly degraded in the digestive tract of mammals (unpublished data, Carbonero et al.). We have transformed wheat (Triticum aestivum L.) with the Itrl gene encoding the BTICMe (Altpeter et al. 1998), in order to evaluate its potential for improvement of resistance against a major storage pest in many developing countries: The Angoumois Grain Moth (Sitotroga cerealella, Lepidoptera: Gelechiidae)