No description available.

No description available.

Viruses can affect plant-insect interactions by altering emission of plant volatile organic compounds (VOCs). Previous work in the lab suggested that VOCs emitted by tomato (Solanum lycopersicum) plants infected with cucumber mosaic virus (CMV) were more attractive to bumblebees (Bombus terrestris) in free choice assays. I extended this work using Arabidopsis thaliana mutants with lesions in genes encoding factors in RNA silencing. In conditioning assays, I confirmed that plant VOC emission is controlled in part by the microRNA regulatory pathway. I used gas chromatography coupled to mass spectrometry and principal component analysis to confirm that CMV infection caused changes in VOC emission by tomato. VOCs collected from non-flowering mock-inoculated and CMV-infected plants were qualitatively distinct from each other. CMV-infected plants also released greater quantities of VOCs than mock-inoculated plants. CMV appears to be both ‘turning up the volume’ of plant volatile emission, whilst ‘tuning’ volatile blend composition so as to diminish levels of a repellant signal. These data are likely to explain how bumblebees can discriminate between VOCs emitted by mock-inoculated and CMV-infected plants. To determine if CMV infection of tomato plants affects plant reproductive success, I carried out a series of bumblebee pollination experiments. Bumblebees pollinate tomato by ‘buzzing’ (sonicating) the flowers, which releases pollen and enhances self-fertilization and seed production as well as pollen export. First, I established that CMV-infected tomato plants produced fruits with a lower seed yield than mock-inoculated plants. When single bumblebees were allowed to buzz-pollinate flowers in a small flying arena, the fruit that developed from buzz-pollinated flowers on virus infected plants had significantly more seeds than fruit from non-visited flowers. Subsequent experiments were performed in a large flying arena. Bumblebees consistently spent longer foraging on the mock-inoculated tomato plants but seed yield was increased by bumblebee pollination in both mock-inoculated as well as virus-infected tomato plants. However, although buzz-pollination significantly enhanced seed yield from CMV-infected plants compared to fruit from non-buzz-pollinated flowers, the yield was higher in buzz-pollinated fruits from mock-inoculated plants. Similar experiments were carried out utilizing a transgenic line of tomato that constitutively expresses the green fluorescent protein in order to estimate the level of cross-pollination from either CMV-infected plants to mock-inoculated plants or vice versa. More pollen from virus-infected plants was transferred to mock-inoculated plants than the reciprocal cross. However, some caution is needed in the interpretation of the larger scale experiments because the tomato plants were affected by a fungal infection. I investigated if the defensive plant hormone salicylic acid (SA) affects bee-perceivable VOC emission. Exogenous SA treatment renders non-flowering tomato plants more attractive to bumblebees in free choice experiments in which bees could only perceive VOCs, but bumblebees spent less time visiting SA-treated flowering tomato plants in the glasshouse (when the bumblebees were allowed unimpeded access to the flowers). Taken together, these data provide evidence that virus infection can affect host-pollinator interactions. Speculatively, CMV infection may change the fitness of susceptible plants via changes in production of pollinator-attractive VOCs and this may affect the balance of resistant or susceptible plants within the host population.

A soja (Glycine max) é uma das culturas mais importantes do mundo, os seus grãos servem tanto para a alimentação quanto para a extração de óleo para a fabricação do biodiesel. O vírus do mosaico do pepino (CMV, do inglês, “Cucumber mosaic virus”) é um vírus de RNA, patogênico a diversas plantas. O RNA de interferência é um sistema de silenciamento de RNA presente na maioria dos eucariotos no qual precursores de RNA de dupla fita (dsRNA) são processados em pequenos RNAs (sRNAs) de 21-24 nucleotídeos (nt), que podem regular a atividade de genes, elementos genéticos e vírus de uma maneira sequência específica. A integração de vírus de DNA e de retrovírus no genoma do hospedeiro já é bem conhecida tanto para sistemas eucarióticos quanto para procarióticos. Mais recentemente, foi observada a integração de vírus de RNA não retrovirais (NIRVs) em mamíferos. O presente trabalho é o primeiro a demonstrar tal evento no genoma de plantas. A partir das sequências dos sRNAs de 19-24 nt de 15 bibliotecas de sRNAs sequenciados de amostras de tecidos de soja, foram montadas sequências contíguas (“contigs”) pelo programa SOAP, algumas das quais apresentaram homologia de sequência ao RNA 1 do CMV. Por montagem de novo desses contigs foi obtida uma sequência de 3.092 nt do RNA 1 do CMV, presente em todas as bibliotecas pesquisadas de pelo menos cinco cultivares diferentes de soja. A presença dessa sequência foi confirmada em outras sete cultivares, exceto em "Willians". Foi observada uma maior presença de sRNAs derivados do CMV senso do que anti-senso nas 15 bibliotecas sequenciadas. Os sRNAs de 22-nt foram os mais abundantes. Para o vírus da mancha da vagem do feijoeiro (BPMV, do inglês “Bean pod mottle virus”) presente em uma das bibliotecas, os sRNAs de 21-nt e 22-nt representaram em torno de 80% do total de sRNAs. Foram encontrados sRNAs que variaram sob estresse biótico (Phakospora pachyrhizi) e abiótico (seca) e entre diferentes cultivares. A expressão do RNA 1 aumentou nas plantas sob estresse. Provavelmente o evento de integração ocorreu via recombinação à um retrotransposon. / The Soybean (Glycine max) is one of the world's most important crops, its seeds are used both as food and for the extraction of oil to manufacture biodiesel. The Cucumber mosaic virus (CMV) is a pathogenic RNA virus of plants. The RNA interference is a system of RNA silencing present in most eukaryotes in which precursors of double-stranded RNA (dsRNA) are processed into small RNAs (sRNAs) of 21-24 nucleotides (nt), which can regulate the activity of genes, genetic elements and virus in a sequence-specific manner. The integration of DNA virus and retrovirus into the host genome is well known both for prokaryotic and eukaryotic systems. The integration of non-retroviral RNA virus (NIRVs) in mammals was previously observed, but the present work is the first to demonstrate such an event in a plant genome. The sequences of the sRNAs ranging from 19 to 24 nt, in 15 libraries of sRNAs sequenced from samples of soybean tissues, were assembled in contigs by the program SOAP, with some preentering sequence homology to the RNA 1 of CMV. By de novo assembling of these contigs it was obtained a sequence of 3,092 nt of the CMV RNA 1, present in all libraries surveyed in at least five different varieties of soybeans. The presence of this sequence was confirmed by PCR in seven other cultivars, but in "Williams". We observed a greater presence of sRNAs derived from CMV of sense orientation than antisense in the 15 libraries sequenced. The 22-nt sRNAs were the most abundant. For the Bean pod mottle virus (BPMV), present in one of the libraries, the 21 and 22 nt sRNAs were represented by around 80% of all sRNAs. The sRNAs were found varying under biotic stress (Phakospora pachyrhizi) and abiotic (drought) and among different cultivars. RNA 1 expression increased in plants under stress. Probably the integration event occurred via recombination of a retrotransposon.

Includes bibliographical references (leaves 147-171). Studies factors affecting the rate of epidemic progress of cucumber mosaic virus in Lupinus angustifolius.

Includes bibliographical references (leaves 147-171). / xx, 171 leaves : ill. (some col.), photos ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies factors affecting the rate of epidemic progress of cucumber mosaic virus in Lupinus angustifolius. / Thesis (Ph.D.)--Dept. of Crop Protection, University of Adelaide,1992

Bibliography: leaves 116-117.

Typescript. Primarily to identify a virus which was isolated from a single Gladiolus plant early in 1962 which showed some resemblance to Cucumber mosaic virus. Exemplifies the large differences which may occur in the biological properties of viruses, even though their physico-chemical properties may be similar.

Bibliography: leaves 116-117 / viii, 131, [82] leaves, [20] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1983

A soja (Glycine max) é uma das culturas mais importantes do mundo, os seus grãos servem tanto para a alimentação quanto para a extração de óleo para a fabricação do biodiesel. O vírus do mosaico do pepino (CMV, do inglês, “Cucumber mosaic virus”) é um vírus de RNA, patogênico a diversas plantas. O RNA de interferência é um sistema de silenciamento de RNA presente na maioria dos eucariotos no qual precursores de RNA de dupla fita (dsRNA) são processados em pequenos RNAs (sRNAs) de 21-24 nucleotídeos (nt), que podem regular a atividade de genes, elementos genéticos e vírus de uma maneira sequência específica. A integração de vírus de DNA e de retrovírus no genoma do hospedeiro já é bem conhecida tanto para sistemas eucarióticos quanto para procarióticos. Mais recentemente, foi observada a integração de vírus de RNA não retrovirais (NIRVs) em mamíferos. O presente trabalho é o primeiro a demonstrar tal evento no genoma de plantas. A partir das sequências dos sRNAs de 19-24 nt de 15 bibliotecas de sRNAs sequenciados de amostras de tecidos de soja, foram montadas sequências contíguas (“contigs”) pelo programa SOAP, algumas das quais apresentaram homologia de sequência ao RNA 1 do CMV. Por montagem de novo desses contigs foi obtida uma sequência de 3.092 nt do RNA 1 do CMV, presente em todas as bibliotecas pesquisadas de pelo menos cinco cultivares diferentes de soja. A presença dessa sequência foi confirmada em outras sete cultivares, exceto em "Willians". Foi observada uma maior presença de sRNAs derivados do CMV senso do que anti-senso nas 15 bibliotecas sequenciadas. Os sRNAs de 22-nt foram os mais abundantes. Para o vírus da mancha da vagem do feijoeiro (BPMV, do inglês “Bean pod mottle virus”) presente em uma das bibliotecas, os sRNAs de 21-nt e 22-nt representaram em torno de 80% do total de sRNAs. Foram encontrados sRNAs que variaram sob estresse biótico (Phakospora pachyrhizi) e abiótico (seca) e entre diferentes cultivares. A expressão do RNA 1 aumentou nas plantas sob estresse. Provavelmente o evento de integração ocorreu via recombinação à um retrotransposon. / The Soybean (Glycine max) is one of the world's most important crops, its seeds are used both as food and for the extraction of oil to manufacture biodiesel. The Cucumber mosaic virus (CMV) is a pathogenic RNA virus of plants. The RNA interference is a system of RNA silencing present in most eukaryotes in which precursors of double-stranded RNA (dsRNA) are processed into small RNAs (sRNAs) of 21-24 nucleotides (nt), which can regulate the activity of genes, genetic elements and virus in a sequence-specific manner. The integration of DNA virus and retrovirus into the host genome is well known both for prokaryotic and eukaryotic systems. The integration of non-retroviral RNA virus (NIRVs) in mammals was previously observed, but the present work is the first to demonstrate such an event in a plant genome. The sequences of the sRNAs ranging from 19 to 24 nt, in 15 libraries of sRNAs sequenced from samples of soybean tissues, were assembled in contigs by the program SOAP, with some preentering sequence homology to the RNA 1 of CMV. By de novo assembling of these contigs it was obtained a sequence of 3,092 nt of the CMV RNA 1, present in all libraries surveyed in at least five different varieties of soybeans. The presence of this sequence was confirmed by PCR in seven other cultivars, but in "Williams". We observed a greater presence of sRNAs derived from CMV of sense orientation than antisense in the 15 libraries sequenced. The 22-nt sRNAs were the most abundant. For the Bean pod mottle virus (BPMV), present in one of the libraries, the 21 and 22 nt sRNAs were represented by around 80% of all sRNAs. The sRNAs were found varying under biotic stress (Phakospora pachyrhizi) and abiotic (drought) and among different cultivars. RNA 1 expression increased in plants under stress. Probably the integration event occurred via recombination of a retrotransposon.