Diamondback moth compensatory consumption of protease inhibitor‐transformed plants

Abstract

Prior study of the effect of protease inhibitors (PIs) on diamondback moths suggests that moths are resistant to them, so PIs represent an ineffective defence against moths. However, our data suggest that diamondback moths do suffer lower growth rates when they consume plants transformed with potato protease inhibitor (PI2), but that effect is hidden by compensatory consumption. Plants, instead of gaining an advantage by lowering the insect growth rate, suffer a disadvantage as moths consume more tissue to mitigate the effect. Furthermore, PI2, when used in conjunction with another transgenic pesticidal protein, Bt (from Bacillus thuringiensis) counteracts the effectiveness of Bt at protecting plant tissue. Thus, transgenic PIs are not only less effective than previously thought in protecting Brassica plants from diamondback moths, they may actually lead to increased plant damage by the moths.

Constitutive and inducible trypsin proteinase inhibitor production incurs large fitness costs in Nicotiana attenuata

“…However, ecological costs might also be incurred that result from the complicated interactions with other species (2,16), such as the decrease the attractiveness of the pollinators (2,41). Because TPI expression frequently slows the grow rate of insect herbivores by making their digestive processes less efficient (40,42), the fitness benefits of TPI expression may result from extending the period during which larvae can be successfully attacked by natural enemies. Hence without the attraction of natural enemies, TPI expression may not increase plant fitness in environments with herbivores.…”

Herbivory-induced volatiles function as defenses increasing fitness of the native plant Nicotiana attenuata in nature

“…Non-toxic protease inhibitor (PI) proteins, which inhibit protein digestion and thus decrease the availability of organic nitrogen in the form of amino acids (Zavala et al, 2008), are widespread in flowering plants (Hartl et al, 2011), and trypsin protease inhibitors (TPIs) slow the growth of M. sexta on N. attenuata (Zavala et al, 2008). However, herbivores can overcome PIs by producing insensitive or desensitized proteases, inactivating or degrading PIs, eating more plant tissue, and eating more nutritious young tissue (Winterer and Bergelson, 2001; Steppuhn and Baldwin, 2007; Zavala et al, 2008). In the latter two cases, PIs could reduce plant fitness.…”

Biotechnological Approaches for the Control of Insect Pests in Crop Plants

“…When larvae of the diamondback moth consumed transgenic plants expressing the chymotrypsin and trypsin specific potato type II proteinase inhibitor, Pot II, they suffered lower growth rates. However, this did not confer an advantage to the plants because the larvae consumed more tissue to compensate for their decrease in metabolism [13,203]. As a result, the insects maintained population growth rates similar to those of larvae on non-transgenic plants.…”