1. Field of the Invention
The present invention relates to fusion proteins (FP) for mediating, in plants, protection against pathogens; and also means and methods for the production thereof. Moreover, the invention also relates to plant cells, plants, and their progeny, once transformed with constructs encoding the fusion proteins of the invention. Further, the invention also relates to pesticides including at least one fusion protein of the invention.
2. Description of the Related Art
Despite the wide range of pesticides that are available on the market plant disease is a major concern for farmers. Many pesticides are not sufficiently target specific and so result in environmental damage. What is more, even dispersion of pesticide may be difficult to achieve resulting in some crops being undesirably saturated with potentially toxic chemicals and some not receiving adequate protection.
Recent progress has exploited genetic techniques to engineer crops that have an in-built resistance to pathogens. These crops are advantageous because they dispense with the need to use conventional pesticides. Typically, the genetic code of crop plants is modified so that they express a protein that is toxic to at least one selected pathogen. More typically still, the protein is most likely to be effective when ingested by the pathogen and so targets the pathogen when it is at its most damaging. However, it has been found that once ingested by the pathogen these supposedly toxic proteins are degraded by the pathogen's digestive system and so rendered ineffective. There is therefore a need to design a protein that can resist this sort of defence.
We consider that pest management technologies based on insect neuropeptides offer a degree of biological activity, target specificity and environmental compatibility that are lacking in neurotoxic insecticides. However, to date, attempts to deliver such peptides by oral administration have proved unsuccessful. As mentioned, delivery via oral route would be optimal for insect crop protection since it would target the insect at its most damaging time. Accordingly it is thought advantageous to administer such peptides by spraying them on crops to be treated or engineering them into crops to be protected. But unfortunately these neuropeptides are susceptible to environmental degradation and, further, once ingested, they are broken down before they achieve their effect. They therefore need to be protected in some way.
Certain plant lectins show a low level of toxicity when incorporated into an artificial pathogen diet or when expressed in transgenic plants. Thus they are not thought to have any insecticidal properties. However, some have been shown to be resistant to gut proteolysis and can be found in the insect haemolymph following ingestion. Thus, we considered that plant lectins may have the potential to act as carrier members to deliver other peptides to the circulatory system of target species.