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Noctuidae) (Alfonso et al. 1997), whereas the BTICMe inhibitor is rapidly degraded in the digestive tract of mammals (unpublished data,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).