STUDY OF THE GENES DIFFERENTIALLY EXPRESSED DURING THE INTERACTION BETWEEN ASPERGILLUS FLAVUS AND ZEA MAYS.

Aflatoxins are carcinogenic fungal secondary metabolites also produced by Aspergillus flavus which are strictly regulated in many countries due to health hazards. Since the interaction with the host (e.g. Zea mays) affects aflatoxin biosynthesis, we set up an experimental protocol to reproduce in vitro and in vivo the 3 phases, saprophytic, chemotrophic and pathogenic, of the interaction. The saprophytic phase was mimicked by growing A. flavus on dead maize kernels. In the chemotrophic phase, the fungus was grown in an Erlenmeyer flask with a minimal medium, in which a dialysis membrane containing previously wounded and viable maize kernels was submerged. The final phase, the pathogenic one, was performed by wound inoculating A. flavus onto maize ears in the field. We analysed the transcriptome of A. flavus using a custom Affymetrix GeneChip microarray containing all the predicted A. flavus genes. Comparison of expression profiles under the different experimental conditions enabled us to identify trends in gene expression associated with the different phases of A. flavus infection of Zea mays. Moreover, on the basis of microarrays information, the study of A. flavus mutants grown in the aforeaforementioned phases is being performed. The results from this investigation, together with a comparative pathway analysis, will highlight the molecular mechanisms of the fungushost interaction and provide a tool for screening genes whose products are able to drive A. flavus pathogenesis. This, in turn, will provide suggestions for limiting AF contamination of this important feed and foodstuff.