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

Ochratoxin A (OTA) is a neurotoxic, immunotoxic, and teratogenic mycotoxin produced by many <Aspergilli> and <Penicillia>. 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 <A. ochraceus>. In this study we have identified the gene Aomdv1 a homolog of the <Saccharomyces> <cerevisea> gene Scmdv1 that encodes the mitochondrial division protein MDV1. Disruption of the <Aomdv1> locus in a wild type <A. ochraceus> 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 <A. ochraceus>, 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 <A. ochraceus> strain to that of the mutant <Ao&#8710;mdv1> 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 <Aspergilli> in the isolated fungal population compared to <Penicillia> and the presence of three potential OTA producing species; <A. niger>, <P. chrysogenum> and <P. glabrum>.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Campus Only Dissertation

Discipline thesis:degree_discipline

Agricultural Sciences

Year dc:date.available

2012

Author dc:creator

• el mounadi, Kaoutar

Contributors dc:contributor

• Fakhoury, Ahmad

Repository record dc:identifier

https://opensiuc.lib.siu.edu/dissertations/570

OAI identifier oai:identifier

oai:opensiuc.lib.siu.edu:dissertations-1571