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Full-Text Articles in Life Sciences

Understanding The Transcriptional Regulation Of Secondary Cell Wall Biosynthesis In The Model Grass Brachypodium Distachyon, Pubudu Handakumbura Nov 2014

Understanding The Transcriptional Regulation Of Secondary Cell Wall Biosynthesis In The Model Grass Brachypodium Distachyon, Pubudu Handakumbura

Doctoral Dissertations

Secondary cell wall synthesis occurs in specialized cell types following completion of cell enlargement. By virtue of mechanical strength provided by a wall thickened with cellulose, hemicelluloses, and lignin, these cells can function as water-conducting vessels and provide structural support. Several transcription factor families regulate genes encoding wall synthesis enzymes. Certain NAC and MYB proteins directly bind upstream of structural genes and other transcription factors. The most detailed model of this regulatory network is established predominantly for a eudicot, Arabidopsis thaliana. In grasses, both the patterning and the composition of secondary cell walls are distinct from that of eudicots. These ...


Physiology Of Cold Acclimation And Deacclimation Responses Of Cool-Season Grasses: Carbon And Hormone Metabolism, Xian Guan Nov 2014

Physiology Of Cold Acclimation And Deacclimation Responses Of Cool-Season Grasses: Carbon And Hormone Metabolism, Xian Guan

Masters Theses

Winter injury of cool-season turfgrasses in northern climates is a significant issue, leading to losses in turf cover and subsequent increased inputs for recovery. Despite the different potential causes for winter injury, the overall level of plant freezing tolerance has been shown to account for a majority of the variation in winter survival of grasses. Freezing tolerance is achieved through cold acclimation, based on a series of physiological and biochemical changes that increase cell stability at freezing temperatures. Winter injury can result from insufficient cold acclimation, or rapid cold deacclimation triggered by temperature fluctuations or freeze-thaw cycles. Previous research has ...


Volatile Profiles And Resistance To Herbivory In Eastern Hemlock, Elizabeth A. Mckenzie Nov 2014

Volatile Profiles And Resistance To Herbivory In Eastern Hemlock, Elizabeth A. Mckenzie

Masters Theses

Eastern hemlock hosts the hemlock woolly adelgid, an introduced sap-feeding insect that causes rapid deterioration of the host. Like most conifers, eastern hemlock produces a variety of constitutive and induced defenses, primarily terpenoids. To explore the relationship of terpenoid defenses with adelgid infestations, we artificially infested hemlocks at a forest site and a plantation site, and compared their terpenoid concentrations to those in control trees. Infested trees showed lower terpenoid concentrations than control trees, suggesting that eastern hemlock not only fails to induce production of terpenoids in response to adelgid infestation, but becomes less able to produce carbon-based defenses due ...


Sequence Analysis Of Maize Yellow Stripe3 Candidate Genes, Dennis B. Depaolo Nov 2014

Sequence Analysis Of Maize Yellow Stripe3 Candidate Genes, Dennis B. Depaolo

Masters Theses

The work presented here focuses on the molecular mechanism of phytosiderophore secretion in graminaceous plants. In maize, yellow stripe3 (ys3) is a mutant that is deficient in its ability to secrete iron-chelating compounds of the mugineic acid family known as phytosiderophores. Phytosiderophores are specific to grasses and are used for the acquisition of iron. Genetic linkage mapping of the ys3 locus lead to a region of interest on chromosome 3 defined by marker UMC1773. The sequence of eleven candidate genes (GRMZM2G390345, GRMZM2G390374, GRMZM2G342821, GRMZM5G800764, GRMZM2G502560, GRMZM5G849435, GRMZM2G105766, GRMZM5G876835, GRMZM2G036976, GRMZM2G502563, miR167g) revealed several small deletions and point mutations within the ...


Functional Analysis Of Moss Class Viii Myosin And Its Role In Plant Cell Division, Shu-Zon Wu Aug 2014

Functional Analysis Of Moss Class Viii Myosin And Its Role In Plant Cell Division, Shu-Zon Wu

Doctoral Dissertations

The moss Physcomitrella patens is a great model system for studying plant gene function using reverse genetic approaches. It undergoes efficient gene-targeting by homologous recombination, allowing the generation of specific gene knockout and tagging a gene at its endogenous locus. Additionally, RNAi is quite effective in P. patens, providing an effective tool for rapid gene silencing and phenotypic characterization. Taking advantage of these features, this dissertation described the establishment of a system to perform an unbiased gene-by-gene RNAi assay to screen for tip growth phenotypes in P. patens. A small set of RNAi constructs were tested, within them one gene ...


Assessing Best Management Practices For Improving Switchgrass Establishment And Production, Amir Sadeghpour Aug 2014

Assessing Best Management Practices For Improving Switchgrass Establishment And Production, Amir Sadeghpour

Doctoral Dissertations

Switchgrass (Panicum virgatum L.) is a C4-grass indigenous to North America being considered as the “model” energy crop. Switchgrass is difficult to establish and first-year stand failure often challenge the large scale production of switchgrass. Reliable establishment methods and effective weed management practices to produce a harvestable biomass in the establishment year are required. Also, to maximize the economic viability of switchgrass production, appropriate nutrient management and harvests are needed. Thus, we conducted researches to improve switchgrass establishment and production. These studies ranged from finding the most promising switchgrass variety to adjusting switchgrass seeding rate, determine the most ...


The Roles Of Myosin Xi And Rop In Moss Tip Growth, Graham M. Burkart Aug 2014

The Roles Of Myosin Xi And Rop In Moss Tip Growth, Graham M. Burkart

Doctoral Dissertations

Because of the large number of myosin XI and ROP genes found in many angiosperms, it has been difficult to determine their precise role with respect to tip growth. In contrast, there are only two myosin XI genes in four ROP genes in the moss Physcomitrella patens. To determine their role in tip growth using a loss-of-function approach, I used RNA interference (RNAi) and found that both of these proteins are essential for tip growth. Consistent with a role in tip growth, I show that a functional, full-length fusion of mEGFP to myosin XI accumulates at a subcortical, apical region ...


Production, Marketing, And Handling Practices To Export Mcintosh Apples To Central American Markets, Mildred L. Alvarado Herrera Aug 2014

Production, Marketing, And Handling Practices To Export Mcintosh Apples To Central American Markets, Mildred L. Alvarado Herrera

Doctoral Dissertations

Latin America offers a marketing opportunity for fresh produce, since many countries are entering into global integration and international trade as part of their portfolio of economic growth. However, to take full advantage of these opportunities, many questions associated with the implementation of marketing approaches, fresh produce quality retention, and profitability need be answered before undertaking this business opportunity. When it comes to developing countries such as those in Central America, and in particular - El Salvador, Honduras, and Guatemala - language, culture, technology, competitiveness, regulations, poverty, and other barriers become challenges to enter these markets successfully. In order to better understand ...


Increasing Nutrient Density Of Food Crops Through Soil Fertility Management And Cultivar Selection, Md. J. Meagy Apr 2014

Increasing Nutrient Density Of Food Crops Through Soil Fertility Management And Cultivar Selection, Md. J. Meagy

Doctoral Dissertations

The mineral nutrient density of vegetables has fallen in the past fifty years. As a result, some people are suffering chronic diseases due to shortage of mineral elements in these foods. The causes of this decline in nutritive value of vegetables have been attributed to a depletion of soil fertility and to a decrease in nutrient concentration in modern cultivars of vegetables. Lettuce (Lactuca sativa L.) is the most widely used leafy vegetable around the world. Research is needed to develop a nutrient content of lettuce that was help to supply adequate mineral nutrition to people. The objectives of the ...


Identification And Epidemiological Features Of Important Fungal Species Causing Sooty Blotch On Apples In The Northeastern United States, Angela Marie Madeiras Apr 2014

Identification And Epidemiological Features Of Important Fungal Species Causing Sooty Blotch On Apples In The Northeastern United States, Angela Marie Madeiras

Doctoral Dissertations

The sooty blotch and flyspeck (SBFS) complex causes blemishes on apples in humid, temperate growing regions worldwide. In contrast to flyspeck etiology, the many species of fungi causing sooty blotch (SB) have not been well studied. The first set of objectives in this study was to use PCR to identify SB species isolated from apples and selected reservoir hosts in the northeastern United States, and to identify patterns of species distribution on hosts and among sites. Results indicated that Geastrumia polystigmatis was the predominant species on apples, whereas Peltaster species were more common on reservoir hosts. Species distribution varied among ...