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INRA Versailles-Grignon hosts North Carolina State professor Ralph Dean

The Research Unit for Biology and Risk Management in Agriculture (INRA and AgroParisTech) welcomes Ralph Dean, a specialist in plant phytopathogen genomics, for an eight-month sabbatical.

Ralph Dean is a professor at North Carolina State University (USA).  On May 1, 2016  he began an 8-month sabbatical in the Research Unit for Biology and Risk Management (BIOGER) © R. Dean
Updated on 06/27/2016
Published on 05/13/2016

Ralph Dean is a professor at North Carolina State University (USA). He is also a world renowned expert in mycology and comparative and functional genomics. On May 1, he began an 8-month sabbatical in the Research Unit for Biology and Risk Management (BIOGER).

This unit’s main goal is to provide solutions to societal issues related to the potential spread and evolution of fungal phytopathogens. It also aims to develop sustainable methods for controlling fungal diseases in major crop species. These tasks require a clear understanding of the evolution of pathogens as well as of the emergence and underlying mechanisms of pathogenicity.  

The unexplored world of fungal genomes

The genomes of fungi and especially of fungal phytopathogens contain a large number of transposons, which are mobile DNA sequences that can make copies of themselves and that generally have no known function. Transposons can be found spread across the entire genome or clustered in specific regions. Such regions often display plasticity and harbor an abundance of effector proteins, virulence factors that allow a fungus to infect its host, as well as genes that code for secondary metabolites such as toxins.

The existence of such regions lends support to the idea that different parts of the genome are evolving at different speeds. For instance, more plastic regions appear to contain genes that evolve more rapidly as the species adapts to novel environmental conditions. It may also be that the clustering of genes encoding protein effectors and secondary metabolites is crucial to gene regulation or mutation as phytogenic fungi contend with their hosts’ resistance mechanisms. Finally, genomic plasticity may affect both the general ability of fungal phytopathogens to adapt and their specific capacity to overcome host defenses or even switch hosts. Such adaptation could lead to the emergence of species that are better suited to their environment.

How fungi adapt to abiotic stress and their hosts

During his sabbatical, Dr. Dean will tackle questions related to the evolutionary processes that mediate how fungal phytopathogens respond to abiotic stress and interact with their hosts. When examining host-pathogen relationships, Dr. Dean will be focusing on the wide range of highly plastic effector proteins produced by fungi. In particular, he will exploit three model species with very different lifestyles and genomic structures: Magnaporthe oryzae, which attacks rice; Leptosphaeria maculans, which attacks rapeseed (and potentially other cruciferous plants); and Colletotrichum tofieldiae, which can help its cruciferous hosts acquire phosphorus and thus promotes plant growth (see recent studies by BIOGER).

Dr. Dean will examine diverse genes that may or may not be linked with transposons in the genomes of these model species and will analyze how transposons affect the evolution of genes, especially those involved in stress responses.

The members of BIOGER will be taking advantage of Dr. Dean’s visit to explore topics ranging from infection strategies and techniques to host adaptation and pathogen control methods. His sabbatical promises to be a productive one, filled with numerous collaborative projects and intellectual exchanges.

Associated Division(s):
Plant Health and Environment
Associated Centre(s):