Dissertation
Integrative approaches for understanding metabolism in plant specialized cell types
Doctor of Philosophy (PhD), Washington State University
01/2012
Handle:
https://hdl.handle.net/2376/4113
Abstract
Plants contain specialized tissues/cell types that play important roles in the synthesis of many natural products. Investigation at cell-specific resolution is necessary for understanding the functional specialization of these specific tissues/cells. In this thesis, I applied integrative approaches to investigate the functions of two cell types: (1) the paraveinal mesophyll (PVM) cells in soybean leaves and (2) the epithelial cells (EC) in grapefruit peel. The PVM layer contains cells with unique ultrastructural properties, and several hypotheses have been developed regarding its functions. We describe a cell type-specific transcriptome effort to evaluate the hypothesized role of PVM cells in accumulating vegetative storage proteins (Vsp) and photoassimilate translocation (Chapter 2). Transcripts related to Vsp and certain vegetative lipoxygenase (Vlx) isoforms were significantly enriched in PVM. Potential roles of Vsp and Vlx in phosphate mobilization and defense responses, respectively, are discussed. Another class of genes enriched in PVM cells was related to the facilitated diffusion of sucrose and various other transporter-related processes. In addition, effects of sink removal experiment (repeated clipping of shoot tips) were investigated in soybean (Chapter 3). At transcriptional level we found an induction of hundreds of transcripts with putative roles in the responses to biotic and abiotic stresses. Our transcriptome data sets also indicated potential changes in amino acid and phenylpropanoid metabolism as a response to sink removal, which was confirmed by metabolic profiling. Taken together, we demonstrate that sink removal leads to an up-regulation of stress responses in distant leaves. Epithelial cells lining the secretory cavities of Citrus peel have been hypothesized to be responsible for the synthesis of essential oil, but direct evidence is lacking. Our cell type-specific transcriptome analysis indicated an enrichment of genes involved in the biosynthesis of terpenoids and phenylpropanoids in ECs, implying a significant metabolic specialization in this cell type (Chapter 4). Morphometric analyses demonstrated that secretory cavities are formed during early fruit development, whereas the expansion of cavities and oil accumulation correlates with later stages of fruit expansion. Our studies have laid a foundation for further investigations towards improved our understanding of the regulation of essential oil biosynthetic in Citrus peel.
Supplemental materials that are included in this thesis are: Supplemental Data S2.1, complete list of processed PVMvsPP microarray data; Supplemental Data S3.1, processed soybean microarray data set for chapter 3; Supplemental Data S3.2, meta data regarding the experimental design of microarray experiment; Supplemental Figure S4.1, microscopic evaluation of secretory cavity expansion in grapefruit; Supplemental Table S4.1, analysis of volatile essential oil components of grapefruit; Supplemental Table S4.2, microarray analysis of transcript patterns in grapefruit ECs and PCs; Supplemental Table S4.3, gene ontology analysis of microarray data in chapter 4; Supplemental Table S4.4, primers used for quantitative real-time PCR analyses in chapter 4; Supplemental Table S4.5, cytochrome P450 and O-methyltransferase genes of unknown function enriched in ECs; Supplemental Protocol S4.1, determining the volume distribution of secretory cavities in grapefruit peel.
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Details
- Title
- Integrative approaches for understanding metabolism in plant specialized cell types
- Creators
- Siau Sie Voo
- Contributors
- Bernd M Lange (Advisor)Howard D Grimes (Committee Member)Sanja Roje (Committee Member)Michael Knoblauch (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Program in Molecular Plant Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 146
- Identifiers
- 99900581454801842
- Language
- English
- Resource Type
- Dissertation