@phdthesis{Ogden2022,
  author    = {Ogden, Michael},
  title     = {Uncovering the interplay between nutrient availability and cellulose biosynthesis inhibitor activity},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XI, 124},
  year      = {2022},
  abstract  = {All plant cells are surrounded by a dynamic, carbohydrate-rich extracellular matrix known as the cell wall. Nutrient availability affects cell wall composition via uncharacterized regulatory mechanisms, and cellulose deficient mutants develop a hypersensitive root response to growth on high concentrations of nitrate. Since cell walls account for the bulk of plant biomass, it is important to understand how nutrients regulate cell walls. This could provide important knowledge for directing fertilizer treatments and engineering plants with higher nutrient use efficiency. The direct effect of nitrate on cell wall synthesis was investigated through growth assays on varying concentrations of nitrate, measuring cellulose content of roots and shoots, and assessing cellulose synthase activity (CESA) using live cell imaging with spinning disk confocal microscopy. A forward genetic screen was developed to isolate mutants impaired in nutrient-mediated cell wall regulation, revealing that cellulose biosynthesis inhibitor (CBI) activity is modulated by nutrient availability. Various non-CESA mutants were isolated that displayed CBI resistance, with the majority of mutations causing perturbation of mitochondria-localized proteins. To investigate mitochondrial involvement, the CBI mechanism of action was investigated using a reverse genetic screen, a targeted pharmacological screen, and -omics approaches. The results generated suggest that CBI-induced cellulose inhibition is due to off-target effects. This provides the groundwork to investigate uncharacterized processes of CESA regulation and adds valuable knowledge to the understanding of CBI activity, which could be harnessed to develop new and improved herbicides.},
  language  = {en}
}
@phdthesis{Verbancic2021,
  author    = {Verbancic, Jana},
  title     = {Carbon supply and the regulation of primary cell wall synthesis in Arabidopsis thaliana},
  school      = {Universit{\"a}t Potsdam},
  pages     = {x, 179},
  year      = {2021},
  abstract  = {Cellulose is the most abundant biopolymer on Earth and cell wall (CW) synthesis is one of the major carbon consumers in the plant cell. Structure and several interaction partners of plasma membrane (PM)-bound cellulose synthase (CESA) complexes, CSCs, have been studied extensively, but much less is understood about the signals that activate and translocate CESAs to the PM and how exactly cellulose synthesis is being regulated during the diel cycle. The literature describes CSC regulation possibilities through interactions with accessory proteins upon stress conditions (e.g. CC1), post-translational modifications that regulate CSC speed and their possible anchoring in the PM (e.g. with phosphorylation and S-acylation, respectively). In this thesis, 13CO2 labeling and imaging techniques were employed in the same Arabidopsis seedling growth system to elucidate how and when new carbon is incorporated into cell wall (CW) sugars and UDP-glucose, and to follow CSC behavior during the diel cycle. Additionally, an ubiquitination analysis was performed to investigate a possible mechanism to affect CSC trafficking to and/or from the PM. Carbon is being incorporated into CW glucose at a 3-fold higher rate during the light period in comparison to the night in wild-type seedlings. Furthermore, CSC density at the PM, as an indication of active cellulose synthesizing machinery, is increasing in the light and falling during the night, showing that CW biosynthesis is more active in the light. Therefore, CW synthesis might be regulated by the carbon status of the cell. This regulation is broken in the starchless pgm mutant where light and dark carbon incorporation rates into CW glucose are similar, possibly due to the high soluble sugar content in pgm during the first part of the night. Strikingly, pgm CSC abundance at the PM is constantly low during the whole diel cycle, indicating little or no cellulose synthesis, but can be restored with exogenous sucrose or a longer photoperiod. Ubiquitination was explored as a possible regulating mechanism for translocation of primary CW CSCs from the PM and several potential ubiquitination sites have been identified.. The approach in this thesis enabled to study cellulose/CW synthesis from different angles but in the same growth system, allowing direct comparison of those methodologies, which could help understand the relationship between the amount of available carbon in a plant cell and the cells capacity to synthesize cellulose/CW. Understanding which factors contribute to cellulose synthesis regulation and addressing those fundamental questions can provide essential knowledge to manage the need for increased crop production.},
  language  = {en}
}