Dissertation
COORDINATION OF NITROGEN AND PHOSPHATE STRESS RESPONSES IN SINORHIZOBIUM MELILOTI
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/110954
Abstract
Sinorhizobium meliloti are bacteria capable of nitrogen fixation during symbiosis with legumes. They are an important source of biologically fixed nitrogen that can reduce the dependency of the world population on synthetic nitrogen fertilizers. For symbiosis to occur, bacteria need to persist in soils that may be deficient in required nutrients such as nitrogen and phosphate. Bacterial stress response pathways are used by cells to cope with nutrient limitations. The nitrogen and phosphate stress responses have been characterized in S. meliloti individually and data have recently been published indicating interactions between the two pathways. A key enzyme in the nitrogen stress pathway, glutamine synthetase, was also demonstrated to be regulated by phosphate availability. Through an RNA-Seq experiment, genes were identified that were responding to changes in available nitrogen, phosphate, or both. A number of genes changing in response to both nitrogen and phosphate limitation were identified, which represented a novel way of characterizing and demonstrating the coordination of these genes in the nitrogen and phosphate stress responses of the cell. Among genes responding to both nutrient limitations were a subset with demonstrated dependency on Hfq, an RNA chaperone. sRNAs were also expressed at different levels during nitrogen and phosphate stress, some of which have known interactions with Hfq. I propose that these Hfq-chaperoned sRNAs regulate target transcripts, serve to integrate stress signals, and fine-tune the response of changing transcripts at the translational level. Other genes were identified that are highly connected to key phosphate stress-related genes and have not previously been described as part of the phosphate regulon. Overall, coordination of the nitrogen and phosphate stress pathways was demonstrated by expression changes in a substantial number of genes. Collectively, the data indicate that phosphate stress has larger implications in cellular processes than nitrogen stress, and that cells prioritize responding to phosphate stress more highly than to nitrogen stress.
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Details
- Title
- COORDINATION OF NITROGEN AND PHOSPHATE STRESS RESPONSES IN SINORHIZOBIUM MELILOTI
- Creators
- Kelly Lynn Hagberg
- Contributors
- Michael L Kahn (Advisor)Lisa M Gloss (Committee Member)Bernd M Lange (Committee Member)Linda S Thomashow (Committee Member)Svetlana N Yurgel (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Molecular Biosciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 198
- Identifiers
- 99900581430701842
- Language
- English
- Resource Type
- Dissertation