10th INTERNATIONAL VERTICILLIUM SYMPOSIUM 16-20 ...

DEFENCE GENE RESPONSES IN A PLANT-ENDOPHYTEINTERACTIONH.O. SHITTU, C.D.M. CASTROVERDE, R.N. NAZAR AND E.J. ROBBDepartment of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, CanadaEndophytes can colonize plants with minimal symptoms and substantialbenefit to the host, including a defence against normally virulent pathogens. Craigellatomatoes (Lycopersicon esculentum) can be infected with a virulent wilt pathogen,Verticillium dahliae, race 1, or a non-host isolate, DVD - E6, resulting in susceptibleor tolerant interactions, respectively. The present study sought to examine a plant'sregulatory responses in susceptible, tolerant or mixed interactions, to identify adaptivechanges which can lead to tolerance or even pathogen resistance. A specializedpathogen-specific microarray chip (TVR3) was developed and used, together withRT-PCR mRNA assays, to examine patterns of defence gene expression when plantsfirst were infected with either pathogen or endophyte. The results demonstrate thatthe host clearly detects and responds genetically with either fungus but that theresponse differs significantly depending on the colonization profile. An apparentinterplay between Dvd-E6 and the plant is able to program the plant's defence geneexpression in a manner that significantly improves resistance against the very largepathogen. Supported by NSERC.66