Adaptation of Spodoptera exigua larvae to plant proteinase inhibitors by induction of gut proteinase activity insensitive to inhibition.
Tobacco plants were transformed with a cDNA clone of chymotrypsin/trypsin-specific potato proteinase inhibitor II (PI2) under the control of a constitutive promoter. Although considerable levels of transgene expression could be demonstrated, the growth of Spodoptera exigua larvae fed with detached leaves of PI2-expressing plants was not affected. Analysis of the composition of tryptic gut activity demonstrated that only 18% of the proteinase activity of insects reared on these transgenic plants was sensitive to inhibition by PI2, whereas 78% was sensitive in insects reared on control plants. Larvae had compensated for this loss of tryptic activity by a 2.5-fold induction of new activity that was insensitive to inhibition by PI2. PI2-insensitive proteolytic activity was also induced in response to endogenous proteinase inhibitors of tobacco; therefore, induction of such proteinase activity may represent the mechanism by which insects that feed on plants overcome plant proteinase inhibitor defense.
Jongsma
M A
MA
Department of Molecular Biology, DLO-Centre for Plant Breeding and Reproduction Research (DLO-CPRO), Wageningen, The Netherlands.
Bakker
P L
PL
Peters
J
J
Bosch
D
D
Stiekema
W J
WJ
D000222:Adaptation, Physiological; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D004064:Digestive System / Q000201:enzymology*; D010450:Endopeptidases / Q000096:biosynthesis*; D007700:Kinetics; D007814:Larva; D008969:Molecular Sequence Data; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000096:biosynthesis* / Q000494:pharmacology; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D016133:Polymerase Chain Reaction; D011480:Protease Inhibitors / Q000494:pharmacology*; D015183:Restriction Mapping; D018411:Spodoptera / Q000502:physiology*; D014026:Nicotiana; D014357:Trypsin / Q000378:metabolism*
D017931:DNA Primers; D018076:DNA, Complementary; D010940:Plant Proteins; D011480:Protease Inhibitors; C034104:proteinase inhibitor II protein, plant; D010450:Endopeptidases; D014357:Trypsin