Adaptation of Spodoptera exigua (Lepidoptera : Noctuidae) to barley trypsin inhibitor BTI-CMe expressed in transgenic tobacco

Nicotiana tabacum plants were transformed with the cDNA of barley trypsin i nhibitor BTI-CMe under the control of the 35S CaMV promoter. Although the t ransgene was expressed and the protein was active in the homozygous lines s elected, growth of Spodoptera exigua (Lepidoptera: Noctuidae) larvae reared on transgenic plants was not affected. The protease activity in larval mid gut extracts after 2 days feeding on transformed tobacco leaves from the hi ghest expressing plant showed a reduction of 25% in the trypsin-like activi ty compared to that from insects fed on non-transformed controls. The susce ptibility of digestive serine-proteases to inhibition by BTI-CMe was confir med by activity staining gels. This decrease was compensated with a signifi cant induction of leucine aminopeptidase-like and carboxipeptidase A-like a ctivities, while chymotrypsin-, elastase-, and carboxipeptidase B-like prot eases were not affected.