Engineering of Insect and Nematode Resistance

Today, engineered insect and nematode resistance are becoming an essential part of a sustainable agriculture in both developing and developed countries worldwide. In 2007, insect-resistant plants based on the transgenic technology were grown on an area of 46 million hectares, more than half of it (26.9 million ha) with a stacked trait of herbicide- and insect-resistant seeds and 19.1 million hectares with insect resistance alone (James 2008). So far, several approaches are under discussion. The first one relies on expression of genes of interest in transgenic plants, whose products are non-phytotoxic but strong anti-parasitic, either lethal toxic or interfering with parasites after their take-up by parasites consequently affecting their development and reproduction. Such transgenes can encode enzymatic inhibitors that block physiological processes within the pest, toxic compounds that are then ingested, compounds that bind to signal molecules, enzymes that interfere with the nematode. Alternatively, the anti-feeding approach is aiming at breaking down the feeding structure by the introduction of genes encoding phytotoxic compounds like barnase or ribosome-inactivating proteins which disrupt feeding cells (Atkinson et al. 2003) or by the knockout of genes which are crucial for formation of the feeding structure or for nematode parasitism (Huang et al. 2006). Because this approach strictly relies on promoters as well as genes specific for nematode-feeding cells, the availability of these elements still remains the obstacle for its realization in practice (Atkinson et al. 2003). In the following, engineering insect and nematode resistance are discussed using anti-insect and anti-nematode genes.

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