The negative effects from rising carbon levels have created the need to find alternative energy sources that are more carbon neutral. One such alternative energy source is to use the biomass derived from forest trees to fulfill the need for a renewable alternative fuel. Through increased understanding and optimization of regulatory mechanisms that control wood development the potential exists to increase biomass yield. Transcription factors (TFs) are DNA-binding regulatory proteins capable of either activation or repression by binding to a specific region of DNA, normally located in the 5-prime upstream promoter region of the gene. In the first section of this work, six DNA promoters from wood formation-related genes were screened by the Yeast One-Hybrid (Y1H) assay in efforts to identify novel interacting TFs involved in wood formation. The promoters tested belong to genes involved in lignin biosynthesis, programmed cell death, and cambial zone associated TFs. The promoters were screened against a mini-library composed of TFs expressed 4-fold or higher in differentiating xylem vs phloem-cambium. The Y1H results identified PtrRAD1 with interactions involving several of the promoters screened. Further testing of PtrRAD1 by Yeast Two-Hybrid (Y2H) assay identified a protein-protein interaction (PPI) with poplar DIVARACATA RADIALIS INTERACTING FACTOR (DRIF1). PtrDRIF1 was then used in the Y2H assay and formed PPIs with MYB/SANT domain proteins, homeodomain family (HD) TFs, and cytoskeletal-related proteins. In the second section of this work, PPIs involving PtrDRIF1s' interaction partners were further characterized. PtrDRIF1 is composed of two separate domains, an N-terminal MYB/SANT domain that interacted with the MYB/SANT domain containing PtrRAD1 and PtrDIVARICATA-like proteins, and a C-terminal region containing a Domain of Unknown Function 3755 (DUF3755). The DUF3755 domain interacted with HD family members belonging to the ancient WOX clade and Class II KNOX domain TFs. In addition, PtrDRIF1 was able to form a complex between PtrRAD1 and PtrWOX13c in a Y2H bridge assay. PtrDRIF1 may function as a regulatory module linking cambial cell proliferation, lignification, and cell expansion during growth. Combined, these findings support a role for PtrDRIF1 in regulating aspects of wood formation that may contribute to altering biomass yield. / Ph. D. / Trees are unique among plants since they have extremely long life spans and the ability to generate large quantities of woody biomass. The woody biomass derived from forest trees can function to provide renewable energy in the form of biofuels. The process of wood formation is complex and requires coordinated activation of genes involved in multiple metabolic pathways. Transcription factors (TFs) are DNA-binding regulatory proteins capable of either activation or repression by binding to a specific region of DNA. These protein-DNA interactions regulate gene expression during plant growth and development. In this study, new regulators of genes known to be involved in wood formation were identified using the Yeast One-Hybrid (Y1H) assay. One of the proteins identified, PtrRAD1 had not been previously linked to wood formation and was a candidate for further characterization. Further testing of PtrRAD1 by the Yeast Two-Hybrid (Y2H) assay resulted in identification of a protein-protein interaction with Populus trichocarpa DIVARICATA RADIALIS INTERACTING FACTOR (DRIF1). PtrDRIF1 was then used in the Y2H assay to identify numerous interacting proteins, in addition to those reported previously in other species. Further characterization of PtrDRIF1, identified an N-terminal region capable of forming interactions with MYB/SANT domain proteins, and C-terminal region that interacted with homeodomain proteins. PtrRAD1, PtrDRIF1, and the homeodomain containing PtrWOX13c were able to form a complex in an Y2H-bridge assay. Combined, these findings support a potential role for PtrDRIF1 in regulating wood polarity, wood formation, and stem cell proliferation.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/89363 |
| Date | 09 November 2017 |
| Creators | Petzold, Herman E. III |
| Contributors | Forest Resources and Environmental Conservation, Brunner, Amy Marie, Welbaum, Gregory E., Beers, Eric P., Holliday, Jason A., Dickerman, Allan W. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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