Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Willeford, Kenneth O.

Committee Member

Warburton, Marilyn L.

Committee Member

Shan, Xueyan

Committee Member

Tang, Juliet D.

Date of Degree

1-1-2018

Document Type

Dissertation - Open Access

Major

Molecular Biology

Degree Name

Doctor of Philosophy

Department

Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology

Abstract

The fungus Aspergillus flavus L. is an agricultural threat, particularly for maize (Zea mays L.). Its invasive growth and contamination before and after harvest can lead to the loss of the commodity and cause life threating consequences to humans and livestock that consume a contaminated product. The differential expression profile of two resistant maize inbred lines, Mp313E and Mp719, and two susceptible maize inbred lines, B73 and Va35, were evaluated in the mRNA and protein levels. The experimental designed used allowed to observe the responses of these maize lines to A. flavus inoculation and to the stress caused by wounding on kernels. Candidate genes were selected from a prior published GWAS and pathway analysis for the expression analysis at the mRNA level. Seventeen candidate genes were selected, and gene expression analysis via RT-qPCR was performed for nine of them. Two of characterized candidate genes that showed an upregulation above 2olds in the resistant lines. These genes are involved in oxidation responses and had an associated positive allele effect, e.g. contribute to aflatoxin accumulation. The results indicate that their role is not necessarily to make the plant more susceptible to the accumulation of aflatoxin but rather to alleviate the oxidative stress caused by the fungus. Susceptible lines, in general, did not show any difference in the expression of the selected candidate genes. At the protein level, an in-gel analysis identified a variety of stress-related proteins that were upregulated in response to A. flavus inoculation and to wounding stress in the resistant lines. A list of genes associated to the proteins identified was compiled for further characterizations and possible use as molecular markers in marker-assisted selection of commercial maize lines resistant to A. flavus.

URI

https://hdl.handle.net/11668/18726

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