Vascular wilt diseases affect virtually all plants on Earth, causing high devastation of crops and species in natural ecosystems. Rising temperatures are facilitating the spread of these pathogens to new geographical areas, including central and northern Europe. These threads result from the blockage of the vascular system caused by the proliferation inside these tissues of mainly soil-borne microbes that enter the root through its outer epidermal cells and crosses all root layers until reaching the xylem (Image 1). Here, the microbial proliferation blocks water and nutrient transport, resulting in wilting symptoms characterized by yellow and dry leaves, which eventually causes plant death (Image 2). These infection strategy, that gave them the name of “silent killers”, together with their soil-borne and resilient nature, make the chemical, cultural and biological controls generally ineffective to limit their infection. Indeed, most studies of these infections have been conducted in aerial plant tissues, yet the essential root-colonization stage remains poorly understood, largely due to the difficulty in accessing this organ. In fact, details of the precise root infection strategies and plant defense mechanisms are still unclear for many root vascular-plant pathosystems. The work of our group and others have shown that these vascular pathogens mainly live in the root apoplast, the space outside the plant plasma membranes almost completely occupied by the cell walls. We have shown that the plant cell wall properties and its changes during microbial colonization are essential in the outcome of the interaction and the plant response to the infection.
One of the most aggressive root vascular pathogens is the fungus Fusarium oxysporum (Fo), the biggest threat to worldwide banana production and the cause of high yield losses in crops like potato, that has a great potential in ensuring food security in developing nations, and tomato, the most grown vegetable in the world. Importantly, though pathogenic Fos can be devastating, most Fo strains are actually non-pathogenic and many establish beneficial interactions with the plant, that can reduce disease caused by root vascular pathogens. A main factor for the Fo pathogenicity is the ability to modify the plant cell walls of internal root cell layers. Thus, the overall objectives of our project are (1) understanding how the dynamic remodeling of root cell walls during fungal infection determines the outcome of the interaction and (2) using this knowledge to increase plant resistance to vascular pathogens while maintaining their interaction with beneficial microbes.
Conveniently, pathogen and non-pathogen Fos also infect the model plant Arabidopsis thaliana, making this pathosystem, Arabidopsis-Fo, ideal to reach our goals in a reasonable time-frame. The know-how generated in this project will be transferred to crops as new agricultural practices that will help to achieve food safety worldwide without adversely affecting the ecosystems.
