University, Diss., 2007--Würzburg.

Thesis (Ph.D.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 27, 2006) Vita. Includes bibliographical references.

This thesis describes fundamental biological characteristics of soybean. Main topic of the thesis is finding resistence of twelve soybean varieties to bacterial blight. Virulence of four Pseudomonas syringae pv. glycinea isolates was tested in laboratory conditions to find isolates with the highest virulence, which were then used for testing of selected soybean varieties resistance to this patogen. The highest virulence was found in Šumperk 112 isolate and Žabčice isolate. These isolates were used for testing of soybean varieties resistance. The lowest resistance was found in Moravians variety, low resistance was found in Laurentiana variety and Bru-nensis variety. High resistance was found in Gallec variety and Chinese NM3 variety.

Small RNAs are important regulators for a variety of biological processes, including leaf development, flowering-time, embryogenesis and defense responses. Most ancient miRNAs are conserved among different plant species and well characterized, while young MIRNA genes are considered to be non-conserved, highly species-specific and less well-studied. miR163 is a non-conserved miRNA and its locus has evolved recently by inverted duplication events of its target gene. Previously, we have shown that miR163 acts as a negative regulator of defense response. However, it remains unclear how miR163 and its targets are being regulated in response to pathogen attacks. Here, we further elucidated the molecular controls and the involvement of miR163 and its targets in plant defense response. Elevated level of miR163 was observed by Pst treatment in Arabidopsis thaliana, and this upregulation was found to be important in controlling the accumulation of its targets (PXMT1 and FAMT), to which they were also inducible by Pst treatment. Transcript and protein level analyses in transgenic plants overexpressing miR163-resistant form of PXMT1 or FAMT provided evidence for miR163 in fine-tuning its targets, suggesting that the stress-inducible miR163 and its targets act in concert in affecting defense genes expression. Epigenetically, histone deacetylation was found to involve in the repression of miR163 targets before and after Pst infection. Our findings revealed additional mechanistic insights to the controls and the evolutionary significance of young miRNA in mediating plant defense pathways against biotic stresses.

No description available.

M.Sc. (Biochemistry) / Pseudomonas, as originally defined by Migula (1894), was a genus encompassing an assembly of rod-shaped, Gram-negative, aerobic gammaproteobacteria, possessing one or more polar flagella for motility. This vague description resulted in the misclassification of polarly flagellated proteobacteria that had not been completely characterized. Re-evaluation of the taxonomy of Pseudomonads was set into motion by advancements in molecular biology. Following this revision, Pseudomonads were clustered based on the homogeneity in their 16S rRNA sequence (Anzai et al., 2000). Research on Pseudomonas species has gained momentum owing to their significant prospects in biotechnological processes. Their exploitation for use as cleaning, biocontrol and bioremediation agents dates back to the 1980s (Sebastian and Kolattukudy, 1988; Weller, 1988)...

The major outer membrane protein OprF from Pseudomonas aeruginosa was compared with OprF from the fluorescent phytopathogen Pseudomonas syringae. The P. syringae oprF gene was subcloned and sequenced and found to code for a sequence of 344 amino acids containing a 24 amino acid leader sequence. The mature protein, with a deduced molecular weight of 34,225, contained four cysteine residues and an alanine-proline rich area. Comparison of the P. syringae OprF amino acid sequence with the P. aeruginosa OprF and the E. coli OmpA sequences showed that the sequences were most similar at the carboxy-terrninal ends. Restriction enzyme site heterogeneity near the oprF gene from nine different P. syringae pathovars was determined. All pathovars had a conserved SalI site within the gene and conserved PstI. and BamHI sites near the ends of the gene. The location of the PstI and the SalI sites outside the gene was variable, although similar. Immunological relatedness between P. syringae OprF from the different pathovars and P. aeruginosa OprF was confirmed. Protein OprF from all the pathovars was shown to be 2-mercaptoethanol modifiable and more easily heat modifiable than was OprF from P. aeruginosa. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

Plants rely on innate immunity to perceive and respond to pathogenic microbes. Pathogenic microbes suppress and evade plant immune responses to obtain nutrients and multiply resulting in plant diseases and death. One battleground for the arms race between plants and microbial invaders is located in the leaf intercellular space, specifically between Pseudomonas bacteria and Arabidopsis. This thesis seeks to understand the virulence mechanisms that allow Pseudomonas bacteria to grow within the leaves of Arabidopsis and how the plant immune response reduces pathogen growth and reproduction. Some plant pathogens produce specific extracellular polysaccharides to potentially enhance pathogenicity during infection of plants. The objective of this thesis is to understand the importance of biofilms for Pseudomonas success and determine if Arabidopsis suppresses biofilm formation as part of the plant immune response. It was hypothesized that biofilm formation contributes to Pseudomonas success in planta and Arabidopsis suppresses biofilm formation during PAMP-Triggered Immunity (PTI) to reduce bacterial growth. Wild-type plants and defense mutants were infiltrated with flg22 or mock (water) treatments to induce or mock-induce PTI in plants, followed by observing GFP-expressing Pseudomonas via florescence microscopy to determine if biofilm-like aggregate formation was occurring. In vivo studies in this thesis indicate that biofilm-like aggregate formation contributes to bacterial success during Arabidopsis infection. Additionally, the phytohormone, salicylic acid (SA), accumulates in leaf intercellular spaces of resistant plants during PTI that suppresses biofilm formation, suggesting that SA acts as an anti-microbial and anti-biofilm agent that contributes to the suppression of pathogen growth during plant defense. / Thesis / Master of Science (MSc)

Pseudomonas syringae pv. syringae B728a, an aggressive bacterial pathogen of bean, utilizes large surface populations and extracellular signaling to initiate a fundamental change from an epiphytic to a pathogenic lifestyle. Extracytoplasmic function (ECF) sigma (σ) factors serve as important regulatory factors in responding to various environmental signals. Bioinformatic analysis of the B728a genome has revealed 10 ECF sigma factors, five of which have high levels of sequence similarity to the FecI-type of ECF sigma factors and play a known role in the regulation of various iron transport systems. Because iron is essential for the induction of major virulence factors in B728a, I hypothesized that these FecI-type sigma factors may play a critical role in the bacterium’s transition between lifestyles. Deletion mutants of two FecI-type sigma factors, Psyr_1040 and Psyr_1107, in B728a have been created using homologous recombination based on the phage λ Red recombinase method. This study shows that the B728a FecI-type sigma factors, Psyr_1040 and Psyr_1107 are affected by conditions of iron stress, and influence the expression of putative outer membrane receptors and transmembrane sensors associated with these genes. Moreover, Psyr_1107 contributes to the expression of a cluster of predicted pili assembly genes downstream of it. Mutations in Psyr_1040 and Psyr_1107 affect the population levels of B728a in bean plants, since in planta growth of deletion mutants of B728a lacking Psyr_1040 and Psyr_1107 appears to be slower than wild-type B728a. In this thesis, the possible roles of Psyr_1040 and Psyr_1107 in the adaptation of B728a to a pathogenic lifestyle are addressed using a combination of phenotypic characterization and quantitative real-time PCR (qRT-PCR) analyses.

Orientador: Adriana Zanin Kronka / Banca: Daniela Comelis Bertolin / Banca: Marileia Regina Ferreira / Banca: Ana Paula de Oliveira Amaral Mello / Banca: Edson Luiz Lopes Baldin / Resumo: A pinta bacteriana do tomateiro, causada por Pseudomonas syringae pv. tomato Okabe (Pst), é uma das principais doenças da cultura, pois pode reduzir a qualidade e o rendimento da produção, afetando o mercado de tomates frescos e transformados. A semente de tomate infectada por Pst, além de manter a bactéria viável por um longo período, também é importante por ser uma fonte primária de inóculo, justificando a necessidade de utilização de sementes isentas do patógeno. Desse modo, esse trabalho teve como objetivos avaliar a eficiência da termoterapia e da aplicação de óleos essenciais como alternativas para o tratamento de sementes de tomate, visando ao manejo de Pst. Inicialmente, foi verificada a ação in vitro dos óleos essenciais (OE) de citronela (Cymbopogon nardus (L.) Rendle), capim-limão (Cymbopogon citratus (DC.) Stapf), tomilho (Thymus vulgaris L.) e melaleuca (Melaleuca alternifolia Cheel), nas concentrações de 1%, 2% e 3%, utilizando-se leite em pó (LP - 1%) como emulsificante. Sulfato de estreptomicina (25mg/mL) e água esterilizada + LP foram incluídos como testemunhas. Os OE de tomilho (2 e 3%) e de citronela (nas três concentrações) e o sulfato de estreptomicina inibiram o desenvolvimento da colônia bacteriana, promovendo a formação do halo de inibição. Em seguida, foram conduzidos experimentos independentes, um para testar o tratamento de sementes com os OE selecionados (citronela a 1% e tomilho a 2%) e outro, com a termoterapia (50°C/30' e 50°C/25'). Todos os exp... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The bacterial speck of tomato, caused by the bacterium Pseudomonas syringae pv. tomato (Pst), is among the main diseases of this crop, as it can reduce the quality and production yield, affecting the market of fresh and processed tomatoes. Pstinfected tomato seed, besides maintaining the bacterium viable for a long period, is also important because it is a primary source of inoculum, demonstrating the need of using Pst-free seeds. Thus, the objective of this work was to evaluate the efficiency of thermotherapy and the application of essential oils as alternatives for tomato seeds treatment, aiming at the management of Pst. Initially, the essential oils (EO) of citronella, lemon grass, thyme and tea tree were evaluated in concentrations of 1%, 2% and 3% (powder milk (PM - 1%) was used as emulsifier). Streptomycin sulfate (25mg/mL) and sterile water + PM were included as controls. Thyme (2% and 3%) and citronella (at three concentrations) EO and streptomycin sulfate inhibited the bacterial colonies development, promoting inhibition halo the formation. Then, independent experiments were carried out, one to test the seed treatment with the selected EOs (citronella 1% and thyme 2%) and another with thermotherapy (50°C/30' and 50°C/25'). All experiments were performed in duplicate. The incidence of Pst in seeds, germination and vigor (plant height) were evaluated. All the tested treatments promoted the eradication of Pst in the seeds. Pst presence in the seeds did not interfere in seeds germination, but promoted a reduction in plant height. Treatment with thyme EO resulted in a significant germination and vigor reduction. Thermal treatments (both temperature/exposure time combinations) and 1% citronella EO were found to be viable alternatives for Pst management in tomato seeds / Doutor