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Plant-parasite/pathogen interactions

Head of Group: Dr Sebastian Eves-van den Akker


evesvandenakker,sebastianWe work in areas of Food Security and Plant Pathology. We are trying to understand how plant pathogens and parasites are so successful. Disease is not passive, all pathogens and parasites manipulate their host during infection to promote virulence. One of the ways they are able to do this is by the secretion of "effectors" into the plant, which modify plant physiology to the benefit of the pathogen. We are particularly interested in plant-parasitic nematodes for their remarkable ability to cause existing plant cells to re-differentiate into a novel tissue.

 

Current projects include:

The 'readers' and the 'regulators'

What distinguishes plant-parasitic nematodes from many other plant pathogens is the presence of specialised gland cells that produce effectors. Discrete subsets of the effector repertoire are delivered into the plant in waves, over the course of several weeks. This project aims to understand this spatio-temporally controlled "parasitism programme": how the parasitism process is regulated over time, in the nematode and in the plant. We anticipate a small number of regulators that control the concerted action of a large number of effectors – if we can disrupt the few regulators, we can simultaneously disrupt hundreds of effectors.
We recently discovered the "DOG box": a promoter motif that unifies hundreds of otherwise sequence-unrelated effectors that are expressed in the same gland cell. The DOG box is our first insight into the regulation of the parasitic process. The fact that a single DNA motif unifies these effectors, implies the existence of a 'reader' and/or 'regulator': likely a protein, or protein complex, which coordinates tissue specific-expression through sequence-specific binding to the DOG box. This project will characterise these 'reader' and 'regulators' of parasitism.

The plant development- and immunity-altering 'toolbox'

Plant-parasitic nematodes have the remarkable abilities to suppress plant-immunity, and to cause existing plant cells to re-differentiate into a novel tissue. The extent of host-plant manipulation is rapid and profound: the cell cycle is arrested at G2, and the number and/or size of almost every sub-cellular organelle is drastically increased (Nuclei, endoplasmic reticulum, mitochondria, and plastids).
In a recent effort we have identified a comprehensive list of the 'tools' (effectors) that cyst nematodes use to manipulate their host. It is thus likely that within this effector repertoire lie genes that are able to dictate the outcomes of plant organelle development. This project aim to understand the targets and molecular detail of such effectors.

Plant-parasitic nematode genomes and transcriptomes

Over the last few years we have sequenced genomes and or transcriptomes for nematode species that straddle almost every major phylogenetic bifurcation that gave rise the sedentary endoparasites: the most economically important species. Most notably this includes the completion of the G. rostochiensis genome consortium. We have ongoing genome projects for a number of cyst nematode species, most recently including the Heterodera schachtii genome consortium, and are always looking for interesting species to analyse.

The contribution of horizontal gene transfer to plant-parasitism by nematodes

We have known for some time that the genomes of plant-parasitic nematodes have acquired genes from non-metazoans by horizontal transfer. Many of these genes encode cell-wall degrading/modifying enzymes that appear to be involved in host invasion.
Genome wide analyses of horizontal gene transfer have identified a number of other classes of genes that may be involved in other parts of the infection process. This project will investigate how the biochemistry of proteins encoded by horizontally acquired genes has changed following transfer, and how these functions contribute to plant-parasitism.

Transformation of plant-parasitic nematodes

With the help of BBSRC funding, we recently established the transformation of plant-parasitic nematodes consortium with the goal of coordinating efforts from groups around the world to deliver credible strategies for subsequent development; ultimately leading to a robust transformation method. We are always interested to discuss and test ideas to make transformation for plant-parasitic nematodes a reality.

 

transgenic potato plants
Transgenic potato plants which target nematode genes

 

a thaliana root
Plant parasitic nematode causes tissue re-differentiation in A. thaliana root (stained orange)

 

protein crystals
Protein crystals and

 

crystal structure
first crystal structure of a nematode effector