UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Elevated Temperature Effects on Carotenoid Biosynthesis in the Diploid Strawberry, Fragaria vesca(2015) Jackson, Melantha E.; Sintim, Herman; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Carotenoids, a subfamily of the isoprenoids, are one of the most diverse classes of secondary metabolites distributed throughout nature. They are lipophilic in nature, and include over 600 tetraterpenoid compounds synthesized by plants, bacteria, and fungi. Carotenoids, as the major pigment responsible for the red, yellow, and orange colors of fruits and vegetable, help promote human health and wellness by serving as antioxidants and precursors to vitamin A. Climate changes that threaten plant reproduction, negatively impact crop production worldwide. Little is understood about the chemistry of carotenoids in plant reproductive structures. Insight into the metabolic roles and functions of carotenoids in plant reproduction and, the effects of abiotic stresses on carotenoid biosynthesis in these structures would globally impact agriculture production by reducing yield loss. The potential for these metabolites to protect the reproductive structures under elevated temperature stress was assessed using biochemical analysis, genomics, and genetic studies. Fourteen candidate genes involved in carotenoid biosynthesis were identified, revealing three small gene families. Quantitative real-time polymerase chain reaction (qPCR) expression analysis of these genes and targeted metabolic profiling using liquid chromatography-high resolution mass spectrometry (LC-HRMS) throughout plant development under control and moderately elevated temperature stress showed that gene expression and metabolite accumulation are tissue specific and differentially responsive to elevated temperature stress. Three phytoene synthase genes were identified and characterized. Genomic analyses revealed that the PSY gene family exhibits functional diversity in plant tissues, both with respect to location and stage of development, as well as in response to abiotic stress.Item Molecular and Genetic Analysis of Flower Development in Arabidopsis thaliana and the Diploid Strawberry, Fragaria vesca(2012) Hollender, Courtney Allison; Liu, Zhongchi; Cell Biology & Molecular Genetics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In a world with a warming climate and a rapidly growing population, plant biology is becoming a field of increasing importance. Deciphering the molecular and genetic mechanisms behind the development of the flower, the fruit and seed progenitor, will enhance the agricultural productivity needed to ensure a sustainable food supply. My PhD research ties in with this need by furthering the basic knowledge of the mechanisms underlying flower development in two ways. First, using Arabidopsis thaliana, the classic model plant, I investigated the regulation of a gene, SPATULA (SPT), necessary for the proper development of the gynoecium, the female flower organ that, upon fertilization, directly gives rise to fruit. For flower and fruit to properly develop, the expression of SPT, must be tightly regulated both spatially and temporally. My research examined the mechanism of transcriptional repression of SPT in the sepals and petals by several interacting transcription factors (LEUNIG, SEUSS, APETALA2) and the molecular and genetic interaction between ETTIN and SPT in patterning gynoecium. The second focus of my research was to develop Fragaria vesca (the diploid strawberry), as a model Rosaceae for the study of flower and fruit development. Arabidopsis has much value as a small, fast growing, flowering plant with a multitude of genetic and genomic resources, however the flower of this mustard family weed is not representative of all crop flowers. The Rosaceae family, including many agriculturally important fruit trees such as apple, peach, blackberry, and strawberry, warrants its own model plant to investigate the distinct mechanisms behind their unique reproductive biology. Toward developing F. vesca as the model plant for studying Rosaceae flowers, I characterized and described developmental progression of F. vesca flowers morphologically through scanning electron microscopy and histological analysis as well as molecularly through transcriptomes and in situ hybridization. In addition, I pioneered a small-scale mutagenesis screen of F. vesca that will lead to future genetic resources. My thesis work places the groundwork for future discoveries in F. vesca and Rosaceae and benefits research, education, and agricultural applications for the Rosaceae and the plant biology communities.