Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 84-109).

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: 128-132)

Thesis (Ph.D.)--Baylor University, 2009. / Includes bibliographical references (p. 172-194).

M.Sc. / Plants produce volatile organic compounds in response to certain elicitors and environments. These compounds have a variety of functions, including the attraction of insects for pollination and seed dispersal, responses to both abiotic and biotic stresses and the priming or sensitizing of neighbouring plants for subsequent attack. The majority of the volatile blend is made up of terpenoid compounds and these compounds are formed through the action of an important class of enzymes termed Terpene Synthases. Lipopolysaccharides form part of the cell surface of Gram-negative bacteria and they are classed as “pathogen-associated molecular pattern molecules” and are thought to induce defence responses in plants by influencing different metabolic pathways that could ultimately result in the production of defence volatiles. LPS from Burkholderia cepacia that has been reported to induce the oxidative burst, the nitric oxide burst and changes in cytosolic calcium concentrations, was used in this study. In order to analyse the volatiles, Single-Drop Microextraction and Solid-Phase Microextraction were used as static headspace sampling techniques that allow the preconcentration of volatile analytes prior to analysis. Both these techniques are fast, simple and equilibrium based and both allow for minimal sample size and preparation. Luminometry was performed in order to test the efficacy of LPS and to determine if LPS is able to induce the oxidative burst in Arabidopsis thaliana. Histochemical staining of transgenic plants containing the PR1:GUS and PDF:GUS reporter gene constructs was performed in order to determine which signalling pathway LPS follows, either the jasmonic acid pathway or the salicylic acid pathway. SPME was then used to extract samples from both time and concentration studies. The time studies involved incubation times of 0 h, 2 h, 4 h and 6 h and 0 d, 1 d, 2 d and 3 d respectively, while the concentration studies involved using LPS concentrations of 0, 20 μg/ml, 40 μg/ml, 60 μg/ml, 80 μg/ml and 100 μg/ml. SPME was also used for the comparision of two A. thaliana ecotypes (Columbia and C24) as well as two A. thaliana knock-out lines (At5g44630 – multi-product sesquiterpene synthase and At5g23960 – (E)-β-caryophyllene synthase), and finally it was used for the sampling of A. thaliana leaf tissue. SDME was used to compare two solvents, namely octane and toluene and these results were compared to the SPME results. GC-MS was used only for the identification of volatiles with both SPME and SDME. Finally, GC-MS was used with SPME to identify volatiles that are produced by leaf tissue after priming.

Plant cysteine proteinase inhibitors or also called phytocystatins inhibit the action of cysteine proteinases in plants. These proteinases are involved in many developmental processes by degrading proteins. In this study possible effects of an exogenous oryzacystatin-I (OC-I) expressed in transformed tobacco has been investigated. By challenging OC-I expressing and non-expressing tobacco with drought and heat stress, OC-I transcription and translation were not affected in OC-I expressing plants and plant extracts from stressed plants containing the inhibitor inhibited papain activity in vitro. Further, plant growth and photosynthesis was not greatly different under the selected growth conditions in both plant types under stress and non-stress conditions. However, OC-I expressing plants showed slightly lower photosynthetic rate, were shorter and had a higher lower dry mass production under non-stress condition. By applying cDNA Representational Difference Analysis (cDNA-RDA) to detect differentially expressed genes in the two types of plants, a gene coding for the light harvesting chlorophyll a/b binding protein gene (lhcb1) of photosystem II (LHC II) was isolated from non-OCI expressing plants. Northern blot analysis showed lower transcript accumulation of the lhcb gene in OCI-expressing plants both under non-stress and stress conditions, which was accompanied by lower chlorophyll content in OC-I expressing plants. Furthermore, plants benefited from OC-I expression by protection of a variety of expressed proteins against degradation. Identification of possible target cysteine proteinases for OC-I in tobacco resulted in the isolation, cloning and characterization of two new papain-like cysteine proteinases from tobacco designated NtCP1 and NtCP2. NtCP1 was expressed only in senescent leaves and it was not induced in mature green leaves upon exposure to drought or heat stress. NtCP1 has therefore a possible potential as a developmental senescence marker in tobacco. In contrast, NtCP2, which was expressed in mature green leaves, has a high similarity to KDEL-tailed cysteine proteinases that are involved in programmed cell death. Both drought and heat decreased NtCP2 transcript abundance in mature green leaves. Overall, this study has provided evidence that expression of exogenous OC-I does not significantly improve plant performance in tobacco in terms of physiological traits under drought and heat stress but provides protection in terms of stability of protein expression by possibly interacting with endogenous tobacco cysteine proteinases. Further detailed studies are suggested on the interaction of endogenous cysteine proteinases and exogenous phytocystatins to elucidate in more detail the type of interaction. Copyright 2006, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Beyene, G 2006, Gene expression and plant performance in oryzacystatin-I expressing transformed tobacco (Nicotiana tabacum L. cv Samsun) plants under abiotic stress, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-12052006-144409 / > / Thesis (PhD (Botany))--University of Pretoria, 2006. / Plant Science / unrestricted

Potato (Solanum tuberosum L.) is the world's fourth largest food crop and large financial losses are incurred each year from wound and bruise related injuries. However, little is known about the coordinate induction of genes that may be associated with, or mark major wound-healing and periderm maturation events. Also, one of the key defense mechanisms for potato tubers is the robust barrier provided by the phellem (skin) of the native periderm. Many biological processes are involved in the formation of this stout tissue. However, little is known about induction of genes that may be associated with this process. The objectives of this research were to molecularly assess the processes of wound periderm development and maturation, and native periderm maturation in potato tubers. In this study, these processes were determined in coordination with expression profiles of selected genes. The cell cycle, cell wall protein, and pectin methyl esterase genes were determined from two diverse potato genotypes and two harvests NDTX4271-5R (ND) and Russet Burbank (RB) tubers; 2008 and 2009 harvests. Cell cycle genes encoding epidermal growth factor binding protein (StEBP), cyclin-dependent kinase B (StCDKB), and cyclin-dependent kinase regulatory subunit (StCKS1At) expression profiles were coordinated with related phellogen formation and the induction and cessation of phellem cell formation. Genes encoding the structural cell wall proteins extensin (StExt1) and extensin-like (StExtlk) expression profiles suggested involvement with closing layer formation and subsequent phellem cell layer formations. The coordinate induction and expression profile of StTLRP, a gene encoding a cell wall strengthening "tyrosine- and lysine-rich protein," suggested a role in the formation of the closing layer followed by phellem cell generation and lastly cell wall thickening in nonmeristematic phellogen cells. StPME and StPrePME expression increased during periderm development, implicating involvement in modifications for closing layer and phellem cell formation. Collectively, these results indicate that the genes monitored were involved in and their expression profiles markedly coordinated with periderm formation and the on-set of periderm maturation; results were more influenced by harvest than genotype. Importantly, StTLRP was the only gene examined that may be involved in phellogen cell wall strengthening or thickening after cessation of cell division.

No description available.

Understanding the genetic regulation of the response to wounding and wound healing in fruiting plants is imperative to maintaining agricultural sustainability, preserving the quality of food supplies, and ensuring the economic viability of agriculture. Many genes are known to be induced by wounding, providing both structural repair and defense. The KED gene in tobacco (Nicotiana tabacum) has been shown to be induced by wounding. We have identified its homologue gene in tomato (Solanum lycopersicum) that we named SlKED. We have analyzed gene expression pattern of SlKED through tomato growth and development and in response to wounding as well as hormonal and inhibitor treatments. We found that the plant hormone ethylene played a major role in the expression of SlKED. To further identify evidence for physiological and transductional functions of KED and SlKED, the tobacco KED gene was introduced to tomato and overexpressed by the fruit tissue-active PUN1 promoter from pepper (Capsicum annuum,). The expression of this gene was compared to the expression of the native SlKED gene and other known wound response genes in both the wild-type and transgenic tomato plants. The upregulation of the native SlKED gene by wounding was significantly muted in the tobacco KED-expressing transgenic plants. The expression of other genes known to be associated with wound response transduction pathways was also altered. Our studies implicate the KED gene in defense mechanisms for mechanical stress in tomato plants. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

No description available.

Les protéines possédant un domaine RING (REALLY INTERESTING NEW GENE) avec une activité E3 ligase sont largement présentes chez les plantes, jouent des rôles importants dans la régulation de plusieurs processus par la reconnaissance d’une protéine cible pour l’ubiquitination. Auparavant, il a été montré que l'expression de PtaRHE1, codant une protéine contenant un domaine RING-H2 avec une activité E3 ligase, est associée à la mise en place de la croissance secondaire chez le peuplier. Dans le cadre de cette thèse, nous avons démontré que PtaRHE1 est mono-ubiquitiné in vitro en présence de l’E2 du peuplier PtaUbC5a. Par hydridation in situ et Western blot, nous montrons que PtaRHRE1 et la protéine correspondante sont exprimés dans les tissus vasculaires de la tige, c'est-à-dire le phloème, le cambium et le xylème. Par comparaison avec les plantes de type sauvage, la sous-expression de PtaRHE1 suite à l’expression d’un microARN (i) a donné lieu à une modification dans la morphologie des fibres secondaire de phloème avec une plus forte densité cellulaire et des paroi de fibres plus mince, (ii) à une modification de la qualité de lignine avec moins d’unité S au niveau des tissus de l’écorce, ces résultats suggèrent un rôle de PtaRHE1 dans la formation et / ou la maturation des fibres. La sur-expression de PtaRHE1 chez les peupliers engendre un phénotype pléiotropique caractérisé par l’enroulement des feuilles et une inhibition du développement racinaire. L’expression du gène codant pour le facteur de transcription WRKY23 est positivement corrélée à celui de PtaRHE1 dans le xylème de la tige des lignées sur-exprimant ou sous-exprimant PtaRHE1. Sur base d’un modèle, nous suggérons un rôle pour le couple PtaRHE1/PtaWRKY23 dans le développement des tissus vasculaires. De plus, nous avons montré que l'expression de PtaRHE1 et l'accumulation de la protéine correspondante sont modulées par l'humidité de l’air et du sol ainsi que par l'acide abscissique. Les informations présentées dans ce travail indiquent un rôle de PtaRHE1 au cours de développement de la plante ainsi que pendant la réponse au stress biotique et abiotique / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished