Manitoba is the second largest potato producer in Canada after Prince Edward Island. This crop faces many disease problems including the most famous and devastating one, late blight, caused by the oomycete pathogen Phytophthora infestans. More than 150 years have elapsed since this disease caused the Irish potato famine, but strategies for managing it often remain unsustainable and costly. With the advent of molecular biology, genetic engineering, and now, genomics-based approaches, it may be possible to initiate studies which will address important questions regarding very complex host-pathogen interactions. Dr. Daayf’s lab has shown that the most aggressive strains of P. infestans suppress potato defense mechanisms, through transcriptional inhibition of PAL and HMGR pathways. Therefore, the objective of the current study was to carry out a molecular characterization of potato defense suppression by Phytophthora infestans. Gene expression profiling was accomplished by developing a new subtractive hybridization (SH)/cDNA-AFLP combinational approach. This approach is a gel-based subtractive hybridization profiling technique that uses the advantages of cDNA-AFLP and subtractive hybridization in order to amplify cDNA products in a polyacrylamide gel and remove the constitutively/commonly expressed sequences. Using this approach differentially expressed genes involved in the potato-Phytophthora infestans interaction were identified. These included genes potentially controlling pathogenesis or avr genes in P. infestans as well as those potentially involved in potato resistance or susceptibility to this pathogen. Using the subtractive hybridization (SH)/cDNA-AFLP combinational approach, DOXP-MEP pathway genes were identified for first time in potato and its regulation in response to the oomycete P. infestans. The DOXP-MEP pathway, also called the non-mevalonate route is an alternative terpenoids' biosynthetic route that was discovered first in eubacteria and soon after in photosynthetic organisms such as higher plants, algae as well as in cyanobacteria. In addition, potato plants treated with glucans extracted from P. infestans, the elicitor eicosapentanoic acid (EPA) and P. infestans isolates were analyzed to study the accumulation of phenolic compounds and expression level of genes from the phenylpropanoid, mevalonate and DOXP-MEP pathway.

Manitoba is the second largest potato producer in Canada after Prince Edward Island. This crop faces many disease problems including the most famous and devastating one, late blight, caused by the oomycete pathogen Phytophthora infestans. More than 150 years have elapsed since this disease caused the Irish potato famine, but strategies for managing it often remain unsustainable and costly. With the advent of molecular biology, genetic engineering, and now, genomics-based approaches, it may be possible to initiate studies which will address important questions regarding very complex host-pathogen interactions. Dr. Daayf’s lab has shown that the most aggressive strains of P. infestans suppress potato defense mechanisms, through transcriptional inhibition of PAL and HMGR pathways. Therefore, the objective of the current study was to carry out a molecular characterization of potato defense suppression by Phytophthora infestans. Gene expression profiling was accomplished by developing a new subtractive hybridization (SH)/cDNA-AFLP combinational approach. This approach is a gel-based subtractive hybridization profiling technique that uses the advantages of cDNA-AFLP and subtractive hybridization in order to amplify cDNA products in a polyacrylamide gel and remove the constitutively/commonly expressed sequences. Using this approach differentially expressed genes involved in the potato-Phytophthora infestans interaction were identified. These included genes potentially controlling pathogenesis or avr genes in P. infestans as well as those potentially involved in potato resistance or susceptibility to this pathogen. Using the subtractive hybridization (SH)/cDNA-AFLP combinational approach, DOXP-MEP pathway genes were identified for first time in potato and its regulation in response to the oomycete P. infestans. The DOXP-MEP pathway, also called the non-mevalonate route is an alternative terpenoids' biosynthetic route that was discovered first in eubacteria and soon after in photosynthetic organisms such as higher plants, algae as well as in cyanobacteria. In addition, potato plants treated with glucans extracted from P. infestans, the elicitor eicosapentanoic acid (EPA) and P. infestans isolates were analyzed to study the accumulation of phenolic compounds and expression level of genes from the phenylpropanoid, mevalonate and DOXP-MEP pathway.

Köln, University, Diss., 2002.

En la actualidad, según la Organización Mundial de la Salud (OMS) 2008, se calcula que existe entre 16 a 18 millones de personas a nivel mundial afectadas por el parásito Trypanosoma cruzi, cuyo vector principal es Triatoma infestans. En nuestro país, la enfermedad se presenta en forma endémica en la región sur afectando principalmente a los departamentos costeros de Ica, Arequipa, Moquegua y Tacna. La falta de conocimiento del vector y la mala implementación de programas para su control, han dado como resultado altos índices de mortandad en la población y la adaptación cada vez mejor del insecto al ambiente doméstico y por ende al ser humano. En el presente trabajo, utilizando individuos nativos de Triatoma infestans pertenecientes a las localidades de Santa Rita de Siguas y Nazca, se confirmo el número cromosómico, y aplicando la técnica del bandeo “C”, utilizada para identificar los bloques de heterocromatina y usarlos como marcadores cromosómicos diferenciando el genoma andino del no andino en las poblaciones en estudio. Mediante la posición de los bloques heterocromáticos se han detectado polimorfismos cromosómicos en número y posición a nivel de los autosomas de los individuos intra e interpoblacionales, y se ha podido determinar el tipo de genoma (andino o no andino) para las poblaciones estudiadas. Por primera vez se evidencia la presencia de población con genoma del grupo andino (población de Ica) que aparece a baja altitud. Palabras clave: Bandeo C, Santa Rita de Siguas, Nazca, polimorfismos cromosómicos, bloques de heterocromatina. / --- Currently, according to the World Health Organization (WHO) 2008, it is estimated that between 16 and 18 million people worldwide are affected by the parasite Trypanosoma cruzi, which main vector is Triatoma infestans. The path vector of disease transmission is the main cause of the high levels of disease and mortality. In our country, the disease occurs endemically in the southern region, mainly affecting the coastal departments of Ica, Arequipa, Moquegua and Tacna. The lack of knowledge of the vector and poor implementation of programs for its control, result in high mortality rates in the population and the best ever adaptation of the insect to the home environment, consequently to humans. In the present work, using native individuals of Triatoma infestans from endemic areas for Chagas disease, belonging to the villages of Santa Rita de Siguas and Nazca, and applying cytogenetic techniques such as squash technique it was confirmed the chromosome number. The C-banding technique was used to determinate heterochromatic zones along the chromosome fiber, which allowed the identification of heterochromatin blocks so that they could be used as chromosomal markers in order to be able to differentiate the Andean genome from the no- Andean one in the populations studied. By the position of heterochromatic blocks, chromosomal polymorphisms were detected at the number and position of the autosomes of individuals within and between populations, and the type of genome has been detected (Andean or no-Andean) for the populations studied. It is shown, for the first time, the presence of population with the Andean group genome (population of Ica) that appears at low altitude. Key words: C banding, Santa Rita de Siguas, Nazca, chromosomal polymorphisms, heterochromatin blocks.

No description available.

Diseases caused by micro-organisms are still a major threat to the agro-industry worldwide. Diseases not only have negative effects on crop yields, but also they can affect the quality of crops post-harvest. Genetic engineering is one of several strategies that have been developed to control plant diseases and to enhance plant disease resistance to pathogens. Although some genetic strategies have provided plants with enhanced disease resistance, some pathogens can easily overcome this resistance by rapid evolution resulting in a lack of durability in the field. The oomycete Phytophthora infestans, the causal pathogen of late blight disease of potato, is an example of a crop pathogen that causes a major problem in one of the most important crops worldwide. Many efforts have been made trying to control this pathogen including chemical controls and genetic engineering, but unfortunately it remains a severe problem and the control measures are rarely very successful. Due to the complexity of this pathogen, and to limit the need for chemical control, breeding programmes to incorporate durable forms of genetic resistance are crucially needed. Although, this type of resistance is believed to be effective against all known races of P. infestans and provide in additional some level of general resistance, until now the genetic bases of this type of resistance is still unknown and the molecular mechanisms poorly understood. This project set out to isolate and identify gene sequences that are induced during the compatible interaction between cultured potato plants and P. infestans, specifically those leading to the establishment of durable resistance. It was demonstrated that the potato variety Stirling is capable of developing this type of resistance as judged by the development of resistant shoots during the interaction with Phytophthora. These shoots showed very strong resistance not only to Phytophthora but also to other potato pathogens (R. solani and F. sulphureum) even after two generations of culturing the plants in the absence of the pathogen. The fast production of ROS and the tight deposition of callose surrounding the hypersensitive cells, which deprive the pathogen of nutrients and limit pathogen growth to a small region of the plant, may be important factors in the success of the durable plants in defending themselves against the pathogen attack.

In order to identify potential avirulence factors of <i>Phytophthora infestans</i>, secreted protein profiles of six strains (IPO-0, CBS431.90, IPO-655-2A, IPO-428-2, 88069 and 90128) with different avirulence phenotypes were analysed by proteomics.  The proteins from culture filtrates were visualised on 2D gels with a total number between 350 and 1000.  PiAVR X was found only in avirulent strains and considered therefore as a possible avirulence determinant.  Its expression increased in all strains tested when grown in Modified Henniger medium.  Single nucleotide polymorphisms (SNPs) were detected within a 735 nt fragment of <i>PiAvrX</i> but none was linked to avirulence characteristics.  The consensus EST database facilitated identification of approximately 50% of 45 most abundant proteins excised from strain 88069.  Beta-glucosidase, Pi-NIP2 (<i>Phytophthora infestans</i> necrosis inducing protein-like protein), enoyl CoA hydratase, glutathione S transferase, peptidylprolyl isomerase, acidic chitinase and Pi-PR1 (<i>Phytophthora infestans </i>homologue of plant PR-1 protein) were among the identified proteins with a recognisable signal sequence.  Enolase, quinine-oxido reductase, nucleoside di-phosphate kinase, actin depolymerisation factor, thioredoxin, ubiquitin and 14-3-3 protein were also identified but without a signal peptide.  The occurrence and expression of <i>Pi-nip2, Pi-chi1 </i>and <i>Pi-pr1</i> were confirmed in the strains tested.  Transformants were obtained from <i>P. infestans</i> strain T30-4 via a biolistic particle delivery approach using a single plasmid vector containing <i>Pi-pr1</i>.  Detailed analysis of these transformants did not demonstrate induction of homology-dependent gene silencing.  It was found that transformation rates were different among the tested <i>P. infestans</i> strains.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 110-115) / Microfiche. / xiv, 115 leaves, bound ill. (some col.) 29 cm

Hohenheim, Univ., Diss., 2007.

Thesis (Lic. Ing. Agronómica)--Universidad Católica Boliviana San Pablo, Unidad Académica de Carmen Pampa Carrera de Ingeniería Agronómica, 2003. / Reproduced from copy at BYU's Benson Institute. Includes bibliographical references (leaves 59-63).