Purification of xylanases from the phytopathogenic fungus Fusarium oxysporum f.sp. lycopersici

Xylans, 1,4-linked polymers of xylopyranose, are ubiquitous and prominent components of the cell walls of all land plants. Arabinoxylan can constitute up to 40% of the primary wall in some monocotyledons. Several lines of evidence suggest that xylanases might be a significant biochemical component in the interaction between plants and pathogens. We decided to undertake the purification of some of the xylan-degrading enymes produced in vitro by the fungal pathogen Fusarium oxysporum f.sp. lycopersici (Fol), and their characterization as possible elicitors of stress and defence responses in tomato plants. We purified and characterized four xylanases from Fol. Since they were not detected in infected host tissues nor showed eliciting activity in our experimental conditions, a role as primary aggression as well as recognition factors can be ruled out, in spite of their similarity to the EIX from T. viride. The hypothesis of the researchers who proposed the EIX to be just one of the many members of a family of elicitors is not supported by the results of our work.