Fitness and feeding are affected in the two-spotted stinkbug, Perillus bioculatus, by the cysteine proteinase inhibitor, Oryzacystatin I
1998
Ashouri, A. | Overney, S. | Michaud, D. | Cloutier, C.
Plant resistance to insect pests based on recombinant proteinase inhibitors (PIs) could interfere with natural enemies of target pests, as their own proteolytic systems may also be sensitive to large spectrum PIs. Oryzacystatin I (OCI) is potential insect pest resistance factor currently engineered into a variety of crop plants, including potato Solanum tuberosum. Potential for OCI interfering with female reproduction in Perillus bioculatus, a stinkbug predator of Colorado potato beetle, Leptinotarsa decemlineata, was studied by chronic feeding for 18 days on prey loaded with 1-16 micrograms OCI/day. Mortality of treated females was negligible, but fertility was reduced by up to 50%. Additional dose-dependent effects in reproducing females included delayed oviposition, reduced fecundity, lower egg mass size, and reduced egg eclosion incidence. Females fed for 18 days on OCI at less than or equal to 4 micrograms/day returned to normal oviposition when switched to prey without OCI after 18 days of treatment, but negative effects persisted for at least 1 days at higher doses. Affected reproduction in P. bioculatus is consistent with the use of OCI-sensitive digestive proteinases by this stinkbug. However, azocaseinase activity in whole body extracts of OCI-fed females increased about twofold indicating compensation, and OCI-sensitive proteinases were still present in extracts. When timed for delay to trigger attack on Colorado potato beetle larvae under controlled conditions, stinkbugs feeding on OCI appeared consistently hungrier than controls fed at similar rate, suggesting that predation by stinkbugs exposed to OCI-recombinant foliage would be higher than normal.
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