Author

Zsofia Toth

Date of Graduation

Spring 2011

Degree

Master of Science in Plant Science (Agriculture)

Department

College of Agriculture

Committee Chair

Laszlo Kovacs

Keywords

NAC transcription factor, SA, PM, transformation, promoter regulation

Subject Categories

Plant Sciences

Abstract

Obligate biotrophic pathogens, such as powdery mildew (Erysiphe necator, PM) generate a defense response in susceptible grapevines, including most Vitis vinifera varieties. In 2007, a group observed that PM infection increased salicylic acid (SA) levels in grape (V. Vinifera cv. Cabernet Sauvignon) leaves, which suggested that SA was part of the PM defense pathway. In the same year, around 3,000 V. vinifera genes were tested for reaction to PM and SA using microarray. Most of the genes responded to PM the same way as to SA treatment, but some genes responded only to PM, and not to SA. Among these genes were stilbene synthase genes and a member of the NAC transcription factor gene family. The results of the experiment were also confirmed by quantitative PCR. The results suggested that SA was not required, or required but insufficient in itself, to regulate the expression these genes. This study focused on the VvNAC gene's promoter regulation. The promoter was isolated, fused to a reporter gene and transferred into SA signal transduction-defective Arabidopsis thaliana plants. For plant modification, Agrobacterium-mediated transformation was used. The plants were selected on hygromicyn B-containing plates and confirmed to be transgenic using PCR. PM-induced gene expression in transgenic plants should indicate if the regulation of the VvNAC gene promoter is independent or dependent on SA signal transduction. To identify the responsible regulatory elements, deletion variants were constructed of the promoter and fused to reporter genes. A better understanding of plant-pathogen interactions will enable scientists to engineer PM-resistance in susceptible grape cultivars.

Copyright

© Zsofia Toth

Campus Only

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