Botrytis infection of tobacco leaf

Effector biology and virulence mechanisms

The Effector team researches how pathogens use small secreted proteins to manipulate plant defence systems and infect plants.

Microbial effectors

Effectors are molecules produced by plant pathogenic microbes that manipulate the host plant physiology to the benefit of a pathogen. The most studied effectors are proteins secreted by microbes into the plant apoplast or cytoplasm, but low molecular weight metabolites can also serve as effectors. Depending on the lifestyle of the microbe, effectors participate in the suppression of plant immune responses and cell death (in case of biotrophic or hemi-biotrophic pathogens) or in the induction of plant programmed cell death (in case of necrotrophic pathogens).

More recently, the definition of effectors has been broadened following the discovery that microbial effectors do not always affect a host plant directly, but rather contribute to the establishment of an ecological niche by their growth inhibiting activity on competing microbes (especially in case of root- or xylem-colonizing microbial pathogens). 

Research aims

We study the effector repertoires of biotrophic, hemi-biotrophic and necrotrophic microbial pathogens, with the aim to unravel the contribution of individual effector molecules to disease development and their modes of action. These studies involve (comparative) genomics, transcriptomics, heterologous protein production, biochemistry, molecular genetics and infection experiments.

An important aspect of the research is the use of methods to screen for “effector activity”, either based on suppressing or stimulating plant cell death responses, or on manipulation of defense responses (e.g. oxidative burst). Although effector molecules are considered to contribute to virulence on host plants, they can in some cases be recognized by plant receptor proteins and trigger hypersensitive cell death, resulting in resistance.

Significant research efforts are devoted to studying the dual role of effectors in either promoting disease development or acting as “avirulence factor” that triggers host resistance. By making pathogen mutants that either overexpress an effector protein or entirely lack one or multiple effector gene(s), we can establish the biological relevance of such effector protein(s). We also study structure-function relationships of effectors to understand which protein domains contribute to their disease-promoting or resistance-inducing properties.

Our objective

The overall objective of the research on effector biology is to increase our understanding of the role of effectors in disease development and thereby contribute to improving disease control methods.