The genome sequence for the potato cyst nematode Globodera pallida and its utilisation for improved control

Lead Research Organisation: Wellcome Sanger Institute
Department Name: Research Directorate

Abstract

The aim of this project is to define bases for novel control and enhanced pest management of the potato cyst nematode, Globodera pallida by obtaining and utilising the full genome sequence. The British Potato Council estimates the UK potato production, processing and retail markets to be worth c. £3 billion p.a. and the potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, are the most economically important nematode problems of this industry. They occur in 65% of UK potato land with G. pallida present at 92% of these sites. PCN impose an annual cost in excess of £50 million on UK potato growers and threaten the future of the crop for many growers. Breeding for resistance since the mid 1950s has produced few commercially acceptable varieties with resistance to G. pallida. Currently used chemical control methods are under increasing pressure due to cost, environmental and health concerns and there are no benign alternatives to the currently used compounds. Control of G. pallida is an essential requirement to maintain the competitiveness of U.K. production. For example, the consumer demand for food with no pesticide residues has resulted in Waitrose sourcing all its potatoes from crops that have not received a nematicide treatment (www.waitrose.com). This requires imports from countries with a lower PCN incidence or requires a more extensive agricultural system in the UK. Consumer support is likely for UK produce that avoids pesticide residues or environmental harm and is soundly based on a sustainable approach. This proposal underpins the innovation needed to reach that outcome. Over the next 5 years, Wellcome Trust Sanger Institute will undertake a major genome sequencing programme aimed at nematodes and other helminths that are human or veterinary-important parasites. WTSI is willing to sequence this plant parasitic nematode for comparative genomic studies. Gene identification will be carried out ab initio and by experimental analysis. The scientific outputs of the proposed work will be of relevance to plant nematologists and to the wider scientific community. A G. pallida genome sequence will allow the UK plant nematology community to remain internationally competitive and will enable new collaborative links to be built with researchers working in other fields including plant development, molecular plant pathology and evolution of resistance. The proposal has broad support. The British Potato Council will independently support CASE awards for postgraduate students that will be aligned with the project. Other support is evident from the letters of support from both industry and the scientific community.

Technical Summary

The aim of this project is to define bases for novel control and enhanced pest management of the potato cyst nematode, Globodera pallida, by obtaining the full genome sequence. The UK potato production, processing and retail markets are worth c. £3 billion p.a. and the potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, are the most economically important nematode problems of this industry. They occur in 65% of UK potato land with G. pallida present at 92% of these sites. Breeding for resistance has produced few commercially acceptable varieties with resistance to G. pallida. Currently used chemical control methods are under increasing pressure due to cost, environmental and health concerns. Control of G. pallida is an essential requirement to maintain the competitiveness of U.K. production. Over the next 5 years, Wellcome Trust Sanger Institute will undertake a major genome sequencing programme aimed at nematodes and other helminths that are human or veterinary-important parasites. WTSI is willing to sequence this plant parasitic nematode for comparative genomic studies. The sequencing strategy can be considered as comprising several stages: (1) 1.9 million whole genome shotgun sequencing reads (~8x coverage), 20000 BAC end and 50000 fosmid end reads will be produced (2) initial assembly into contigs (3) generation of larger scaffolds (linked contigs) by automated resequencing (50,000 reads) from selected shotgun clones to extend the length of contigs that were truncated by the presence of GC-rich sequences, secondary structure, etc (4) assembly refinement and annotation. Gene identification will be carried out ab initio and by experimental analysis using tiling arrays.
 
Description The potato cyst nematode Globodera pallida is a major agricultural pathogen, threatening the £3 billion UK potato industry. Potato cyst nematodes are present on 65% of UK potato land, and controlling them costs UK growers in excess of £50 million annually. Mainstream commercial potato varieties show no resistance to Globodera pallida, and increasing controls on the use of nematicides, and increasing concern on the part of consumers about pesticide residues, mean that these nematodes threaten the future of the potato crop for many growers. Novel control and pest management approaches are thus urgently needed for this nematode.

The principal output from this research is a high-quality draft genome sequence of the potato cyst nematode Globodera pallida, which will prove a major resource in developing novel approaches to control this important plant pathogen. It will also be a valuable tool for researchers working with other parasitic nematode species for comparative genomic studies. Sequencing the genome of Globodera pallida proved challenging, as there was significant genetic diversity within the parasite population, confounding standard approaches to assembling the short sequencing 'reads' generated into a single sequence. Producing data from a range of different sequencing platforms allowed us to circumvent this problem and produce a draft sequence for the entire genome.



Genome sequence data itself is of little use without some 'annotation', indicating the putative function of different elements of the sequence, and in particular, which parts of the sequence are predicted to be genes - transcribed as RNA and then (for the most part) translated to produce proteins. To aid this gene finding, we sequenced RNA from two samples for each of eight key stages of the Globodera pallida life cycle, allowing us to unambiguously identify genes. As an additional benefit, these data allow us to infer exactly when each gene is turned on and off, an important clue to the function of the genes.



Advances in sequencing technologies allowed additional sequence data to be generated over and above that originally planned in the project. We have generated sequence for a number of additional G. pallida populations. These include four UK populations that differ in their virulence. We have also generated sequence data from from the closely related species of potato cyst nematode, G. rostochiensis, which differs in its virulence against a key resistance gene found in some potato cultivars. We have also been able to use RNA sequencing to characterise the transcriptomic response of infective juveniles of G. pallida to seven chemical compounds, including nematicides. Expression analysis was carried out after appropriate exposures to chloroquine, dazomet, imidacloprid, thiabendazole, levamisole, fluoxetine and ivermectin, considerably broadening the applied impact of the research.
Exploitation Route Complete knowledge of the genes expressed by potato cyst nematode at the various stages of its lifecycle will provide many opportunites for the development of new management or control strategies for this important crop pest.



Analysis of the data has produced a catalogue of candidate genes involved in initiation of the parasitic interaction with the host potato plant. Such genes will be important targets for the disruption of this process that could lead to plant resistance. One route for achieving this would be to develop plants that produce molecules to specifically target and suppress these genes or others known to be essential to the viability of the nematode.



The data that we have generated characterising the transcriptomic response of infective juveniles of G. pallida to seven chemical compounds, including nematicides, considerably broadens the applied impact of the research. Analysis of the gene complement of the nematode may provide additional targets for the development of new, biosafe nematicides.
All of the genomic data is available to the scientific community and its analysis will continue to provide insights into the biology of Globodera pallida and the molecular basis of its pathology for many years. The transcriptome sequence from eight stages around the Globodera pallida lifecycle and in response to seven chemicals, including nematicides, allows global comparative gene expression to be analysed. Together, this provides probably the most comprehensive transcriptomic dataset for a nematode other than Caenorhabditis elegans and is a major resource for further functional analysis of genes.



The comparative genome and transcriptome sequence produced for more than six populations of G. pallida plus the closely related species G. rostochiensis will provide insights into key determinants of nematode virulence.



Molecular understanding of the interaction between potato cyst nematodes and their host will have important implications for our understanding of plant development, and of how plant development can be controlled. Disrupting this reprogramming process will also be an important target for control of the nematode.
Sectors Agriculture, Food and Drink

URL http://parasite.wormbase.org
 
Description All of the genomic data is available to the scientific community and its analysis will continue to provide insights into the biology of Globodera pallida and the molecular basis of its pathology for many years. The transcriptome sequence from eight stages around the Globodera pallida lifecycle and in response to seven chemicals, including nematicides, allows global comparative gene expression to be analysed. Together, this provides probably the most comprehensive transcriptomic dataset for a nematode other than Caenorhabditis elegans and is a major resource for further functional analysis of genes. The comparative genome and transcriptome sequence produced for more than six populations of G. pallida plus the closely related species G. rostochiensis will provide insights into key determinants of nematode virulence. Molecular understanding of the interaction between potato cyst nematodes and their host will have important implications for our understanding of plant development, and of how plant development can be controlled. Disrupting this reprogramming process will also be an important target for control of the nematode.
 
Title Draft genome for Globodera pallida 
Description Raw data, assemblies and annotation for the Globodera pallida draft genome. The Sanger Institute 
Type Of Material Database/Collection of data 
Year Produced 2012 
Provided To Others? No  
Impact No actual impacts realised to date 
 
Title Globodera pallida comparative genomic data 
Description Comparative genomics data for other strains of Globodera pallida 
Type Of Material Database/Collection of data 
Year Produced 2010 
Provided To Others? No  
Impact No actual impacts realised to date 
URL http://www.sanger.ac.uk/resources/downloads/helminths/globodera-pallida.html
 
Title Globodera pallida transcriptomic data data 
Description RNA-sequencing data for Globodera pallida 
Type Of Material Database/Collection of data 
Year Produced 2012 
Provided To Others? No  
Impact No actual impacts realised to date 
URL http://www.sanger.ac.uk/resources/downloads/helminths/globodera-pallida.html