Biotechnological Prospects for Engineering Insect-Resistant Plants  

Abstract

Insect-resistant crops have been one of the major successes of applying plant genetic engineering technology to agriculture; cotton (Gossypium hirsutum) resistant to lepidopteran larvae (caterpillars) and maize (Zea mays) resistant to both lepidopteran and coleopteran larvae (rootworms) have become widely used in global agriculture and have led to reductions in pesticide usage and lower production costs (Toenniessen et al., 2003;Brookes and Barfoot, 2005).The source of the insecticidal toxins produced in commercial transgenic plants is the soil bacterium Bacillus thuringiensis (Bt). Bt strains show differing specificities of insecticidal activity toward pests, and constitute a large reservoir of genes encoding insecticidal proteins, which are accumulated in the crystalline inclusion bodies produced by the bacterium on sporulation (Cry proteins, Cyt proteins) or expressed during bacterial growth (Vip proteins). The threedomain Cry proteins have been extensively studied; their mechanism of action involves a proteolytic activation step, which occurs in the insect gut after ingestion, followed by interaction of one or both of domains II and III with ''receptors'' on the surface of cells of the insect gut epithelium. This interaction leads to oligomerization of the protein, and domain I is then responsible for the formation of an open channel through the cell membrane . The resulting ionic leakage destroys the cell, leading to breakdown of the gut, bacterial proliferation, and insect death.However, not all pests are adequately targeted by the Bt toxins used at present, and there is still a need to develop solutions to specific problems, such as resistance to sap-sucking pests and pests of stored products. This Update will review some developments to the basic Bt strategy and selected alternative methods for engineering insect resistance.

A viral chitinase enhances oral activity of TMOF

“…This objective is pursued not only in the perspective of finding alternative genes for engineering new insect-resistant plants, which is highly needed (Gatehouse, 2008), but also to develop new bioinsecticides and effective delivery strategies, not exclusively based on the use of transgenic plants. This approach aiming at a sustainable exploitation of insect natural antagonism, obviously applies to a large variety of insect antagonists, which offer a virtually unlimited reservoir of new molecules with insecticide activity (Wethstone and Hammock, 2007).…”

Plant Interactions with Arthropod Herbivores: State of the Field

“…An Update by Gatehouse (2008) in this issue highlights advances in transgenic approaches for creating insect-resistant crops. Enthusiasm for the use of plant proteinase inhibitors for crop protection has been tempered by the realization that insects have the capacity to synthesize, on demand, gut proteases that are insensitive to plant-derived inhibitors.…”

Deleterious effects of plant cystatins against the banana weevil Cosmopolites sordidus

“…By contrast, significant progress has been made in recent years towards the genetic transformation and in vitro regeneration of commercial banana and plantain varieties (Pérez Hernandez et al, 2006;Pommerrenig et al, 2006;Khanna et al, 2007), paving the way to the development of insectresistant transgenic banana lines. A number of recombinant proteins with pesticidal, antidigestive or antifeedant properties have been identified or devised over the years for the development of herbivorous pest-resistant crops by genetic transformation (Carlini and Grossi-de-Sá, 2002;Christou et al, 2006;Gatehouse, 2008;Zhu-Salzman et al, 2008). An engineered version of the rice cysteine protease inhibitor oryzacystatin I (OC-I) (Urwin et al, 1995) was shown, notably, to confer nematode resistance in transgenic banana lines genetically transformed with the corresponding transgene sequence (Atkinson et al, 2004a).…”