Study of Ochratoxin A biosynthesis by Aspergillus ochraceus and incidence of ochratoxigenic fungi on Wine Grapes from Southern Illinois

Author

Kaoutar el mounadi, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2012

Degree Name

Doctor of Philosophy

Department

Agricultural Sciences

First Advisor

Fakhoury, Ahmad

Abstract

Ochratoxin A (OTA) is a neurotoxic, immunotoxic, and teratogenic mycotoxin produced by many and . These organisms infect several plant species at pre-harvest and post-harvest and produce OTA in the infected crops. To date, little is known about the mechanisms that regulate OTA biosynthesis in . In this study we have identified the gene Aomdv1 a homolog of the gene Scmdv1 that encodes the mitochondrial division protein MDV1. Disruption of the locus in a wild type strain results in a block in OTA production accompanied with reduction in conidiation, a defect in beta-oxidation and an abnormal mitochondrial phenotype. A yeast, two-hybrid screen revealed that Aomdv1 interacts with proteins involved in regulating mitochondrial functions necessary for mycotoxin production. To further understand the role of Aomdv1 in OTA production in , we used a cDNA-AFLP differential display approach to compare the gene expression profile of the wild type and the mutant and identify genes related to ochratoxin A biosynthesis. The differentially expressed sequences encoded proteins involved in the regulation of gene expression and proteins related to stress response. Furthermore, we compared the proteomic pattern of the wild type strain to that of the mutant using a 2D-GE technique combined with MALDI-MS. We identified proteins differentially expressed between the two strains and discussed their possible functional roles in OTA production and regulation. Another part of the study included conducting a survey to investigate the mycoflora of grapes grown in Southern Illinois and assess the risk of presence of OTA- producing fungi in these grapes. The study revealed a predominance of in the isolated fungal population compared to and the presence of three potential OTA producing species; , and .