Insect-Resistant Tobacco Plants Harboring an Elderberry Gene

By inserting a gene coding for type-2 ribosome-inactivating protein (SNA-I’) from elderberry (Sambucus nigra), scientists at the Ghent University in Belgium have developed transgenic tobacco lines resistant to several insect species including the beet armyworm and tobacco aphid. Ribosome-inactivating proteins (RIPs) are a group of plant proteins that are capable of catalytically inactivating eukaryotic ribosomes, which are necessary for protein synthesis. RIPs are widespread in the plant kingdom, with various degrees of toxicity. For instance, the RIP ricin from castor beans is highly toxic whereas RIPs from wheat and barley have no reported cytoxicity.

Insecticidal activity of elderberry RIP is well documented and its enzymatic mechanism is well defined. However, the physiological steps by which ribosome inactivation leads to cell death are not well understood. Scientists postulate that RIPs induce cell suicide.

Transgenic plants accumulating elevated levels of RIP in their leaves were found to be capable of resisting insect attack, specifically the tobacco aphid M. nicotianae and the beet armyworm S. exigua, in small-scale trials carried out under controlled conditions. In addition, significant increases in mortality were noted for insects fed on the transgenic lines as compared to wild type plants.

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