Identification and Characterization of Factors That are Important for Nutrient Sensing and Plant Tolerance to Low Nutrient Conditions

Date of Award

Spring 5-15-2011

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Plant & Microbial Biosciences)

Degree Name

Doctor of Philosophy (PhD)

Degree Type



Nutrients are essential for animals and plants. The deficiency of the nutrients significantly reduces plant growth and crop yields. Although it is well-known that plants respond to nutrient deprivation at the physiological and transcriptional levels, many aspects of plant nutrient sensing and signaling as well as tolerance to nutrient deprived conditions are poorly characterized. The aim of the work in this thesis was to identify and characterize the factors that play important roles in nutrient sensing as well as plant tolerance and growth under low nitrogen and potassium conditions. The initial work elucidated the role of ethylene in plant response and tolerance to potassium deprivation in Arabidopsis. Data are presented showing that potassium starvation induced the up-regulation of HAK5, a potassium transporter, and plant root responses such as primary root inhibition and root hair elongation are ethylenedependant indicating that ethylene is a main regulator in low potassium signaling. Subsequent work involved screening of an overexpression library in Arabidopsis that was designed to identify factors that play an important role in plant tolerance and growth under low potassium and nitrogen conditions. The last two chapters describe the detailed work that I have done on two genes that were identified in that screen. One gene isolated is a putative protein kinase and I describe the function and role of this putative kinase, not previously characterized in plants. Loss-of-function of the putative kinase suggested that it plays an important role in root hair elongation, plant growth and vesicular trafficking. The other gene isolated was a glutaredoxin and data are presented on the partial characterization of large family of glutaredoxin genes that appear to be involved in low nitrate signaling pathways. In summary, many factors such as hormones, phosphorylation, and possibly redox regulation play roles in plant growth and tolerance to low nutrients as described in this thesis. These data will help in understanding the fine networks of low nutrient signaling and could be useful in the development of higher-yielding crop plants that use nutrients more efficiently or that are more tolerant to low nutrient environment.


English (en)

Chair and Committee

Daniel P. Schachtman

Committee Members

Douglas L. Chalker, Joseph M. Jez, Robert G. Kranz, Barbara N. Kunkel, Mark P. Running


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