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Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology and Microbiology

First Advisor

Paul J. Rushton


The staggering growth in population with no expansion for arable land, provide enormous pressure to increase food production. However, food production is seriously hampered by abiotic stresses such as drought. To address this issue, crop tolerance to drought must be improved. In order to develop strategies to improve plant responses to water stress, one must understand the regulatory pathways involve in plant’s responses to water stress. One of the major components in the web of regulatory networks is transcription factors. In plants, one of the biggest families is the WRKY transcription factors. In this study, we would like to elucidate the role of WRKY transcription factors in plant responses to water stress. Using tobacco as our model plant, we analyzed the spatial and temporal transcriptome and metabolome profiles of tobacco plants subjected to water stress at different time points (20, 40, 60, 120 and 240 min). Transcriptome profile showed major transcription factor families such as ERF, WRKY, NAC, bHLH and MYB to be highly induced by water stress in both roots and leaves of tobacco. Downstream genes such as late embryogenesis abundant proteins (LEA), dehydrins, aquaporins, raffinose synthase and galactinol synthase where also highly induced. Gene expression profile showed that the gene products from the stress-inducible genes can be group as regulatory proteins and proteins involved in direct protection of the cell from stress. Metabolome profile showed accumulation of proteinogenic amino acids as well as compatible solutes such as proline, trehalose and raffinose. Expression profile of our target genes concurred with our metabolome profile. Promoter analyses of up-regulated WRKY and enzyme-coding genes provided an overview of cis-regulatory elements present in stress-inducible genes. In vivo and in planta analyses of promoter of stress-inducible genes showed responses of transformants to phytohormones and other abiotic stresses.

Library of Congress Subject Headings

Tobacco--Effect of drought on
Tobacco--Effect of stress on


Includes bibliographical references



Number of Pages



South Dakota State University


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