Exploitation of genomic knowledge for sustainable resistance to the crop pest Globodera pallida

Plant parasitic nematodes cause estimated annual losses to global agriculture of $125b . Potato cyst nematode costs the UK potato industry an estimated £50 m/year. Control often depends on nematicides that are both harmful to the environment and possibly human health. They are often essential for economic potato cropping in the UK. The new technology to be used in this work can control plant parasitic nematodes without harming the environment. A protein and the role it plays in a cell can be abolished if the gene that provides the code specifying it becomes inactive. This is a natural effect that probably protecting cells from mobile genetic elements such as certain viruses. Its basis is that the some viruses make a double not the normal single strand of the intermediary molecule (RNA). It is involved in the reading of the genetic code when each new protein molecule is made. The natural gene silencing effect can be induced experimentally by introducing the double stranded form of RNA to a cell. This can cause an organism to silence one of its own genes. This is experimental manipulation is achieved by introducing to a cell a sequence that matches precisely that of the gene to be silenced. This is termed RNA interference (RNAi) and the effect was first demonstrated for the free-living nematode Caenorhabditis elegans after it swallowed dsRNA. The same effect induced by introducing dsRNA to a range of organisms. Plants can be modified to make the dsRNA of interest. RNAi provides a powerful experimental tool. Individual genes of interest can be specifically silenced and the effects of this studied. We established the use of RNAi for analyses to function of particular genes of plant parasitic nematodes. We have identified genes the nematode must express to feed in plants effectively. Others have used the approach to silence the function of individual genes in plants. In parallel we have used other methods to define which plant genes must express locally in roots for a nematode to feed successfully. In this proposal we will express in the potato plant a small number of dsRNA molecules known to silence particular nematode genes. Silencing will occur after the animal has swallowed the dsRNA when feeding from the plant. We will also target a few plant genes that must be active for the nematode to feed normally. The key advantage of the approach is that no novel protein is made. There is no known basis for any particular dsRNA to be harmful in either the human diet or to the environment. It is therefore highly preferable to current use of pesticides or control procedures that are less cost effective. The dsRNA will be driven from a gene switch (promoter) that is naturally active just where the nematode feeds in the root and not in its tubers or leaves. The safe dsRNA will not even be in the potato tubers we eat. The silencing of these genes will prevent the development of the nematode and so stop the damage it causes to the crop. The work will provide an approach that helps meet the urgent need for UK potato growers to reduce pesticide use. It will allow cultivars favoured by consumers but currently damaged by nematode to be widely grown without any risk to food safety. The approach will have no environmental harm and allow natural control of insects to flourish by eliminating pesticides that currently harm them. The approach has wider potential than to be developed in the approach. The current application represents a basis for competitive and sustainable UK potato cropping in an improved environment for invertebrates and those that feed on them in UK potato fields.

Plant parasitic nematodes cause losses to global agriculture of $125b annually. Potato cyst nematodes cost the UK potato industry an estimated £50 m/year. Control often depends on nematicides that are both harmful to the environment and possibly human health. A new biosafe technology will be developed to control plant parasitic nematodes that will have minimum environmental impact. The approach is based on post-translational gene silencing triggered by double stranded RNA, termed RNA interference (RNAi). We established the use of RNAi for functional analysis of plant parasitic nematodes genes, to identify genes nematodes must express to be a successful plant parasites. In parallel work, we have used microarray analysis to identify plant genes upregulated where a female cyst nematode modifies plant cells to form a syncytium. The nematode feeds at this one site and is developmentally committed to it. In this project, we will apply our new knowledge to direct expression of dsRNA in planta. We will use the approach to target nematode and plant genes that are crucial for a compatible host/pathogen interaction. The choice of plant genes has ensured that unwanted effects outside the feeding site are unlikely. Ingestion by the nematode of dsRNA targeted at one of its genes will induce a silencing effect with the detrimental consequences for the parasite. An RNAi effect has already been demonstrated after targeting nematodes genes both in vitro and in planta. We will use the same promoter to restrict expression of dsRNA targeted at either nematode or plant genes. The promoters to be used are up regulated in the feeding cell but show little activity elsewhere in vegetative plant tissues. The dsRNA approach lacks inherent food or environmental hazard and involves no transgenic protein expression for nematode control. This eliminates the perceived consumer or environmental risk associated with transgenic expression of proteins.