Role of polyhydroxybutyrate and glycogen as carbon storage compounds in pea and bean bacteroids

Rhizobium leguminosarum synthesizes polyhydroxybutyrate and glycogen as its main carbon storage compounds. To examine the role of these compounds in bacteroid development and in symbiotic efficiency, single and double mutants of R. legumosarum bv. viciae were made which lack polyhydroxybutyrate synthase (phaC), glycogen synthase (glgA), or both. For comparison, a single phaC mutant also was isolated in a bean-nodulating strain of R. leguminosarum bv. phaseoli. In one large glasshouse trial, the growth of pea plants inoculated with the R. leguminosarum bv. viciae phaC mutant were significantly reduced compared with wild-type-inoculated plants. However, in subsequent glasshouse and growth-room studies, the growth of pea plants inoculated with the mutant were similar to wildtype-inoculated plants. Bean plants were unaffected by the loss of polyhydroxybutyrate biosynthesis in bacteroids. Pea plants nodulated by a glycogen synthase mutants or the glgA/phaC double mutant, grew as well as the wild type in growth-room experiments. Light and electron micrographs revealed that pea nodules infected with the glgA mutant accumulated large amounts of starch in the II/III interzone. This suggests that glycogen may be the dominant carbon storage compound in pea bacteroids. Polyhydroxybutyrate was present in bacteria in the infection thread of pea plants but was broken down during bacteroid formation. In nodules infected with a phaC mutant of R. leguminosarum bv. viciae, there was a drop in the amount of starch in the II/III interzone, where bacteroids form. Therefore, we propose a carbon burst hypothesis for bacteroid formation, where polyhydroxybutyrate accumulated by bacteria is degraded to fuel bacteroid differentiation.

Water uptake and use by morphologically contrasting maize/pea cultivars in sole and intercrops in temperate conditions

Growth and water use of sole crops and intercrops of morphologically contrasting maize and pea cultivars were measured in two years. The maize cultivars were Nancis with erectophile and Sophy with planophile leaves and the pea cultivars Maro a leafy pea and Princess a semi-leafless pea. In the first part of the season water use was lower for sole maize but intercrops and sole pea used similar amounts of water. By 90 days after sowing, when peas had matured, all crops had used similar amounts of water. Maize had slightly greater water use efficiency than peas. Cultivars Nancis and Princess tended to have greater water use efficiency than Sophy and Maro respectively. Intercrops produced more dry matter than sole crops and therefore had consistently greater water use efficiencies.

Regulation of L-alanine dehydrogenase in Rhizobium leguminosarum bv. viciae and its role in pea nodules

Alanine dehydrogenase (AldA) is the principal enzyme with which pea bacteroids synthesize alanine de novo. In free-living culture, AMA activity is induced by carboxylic acids (succinate, malate, and pyruvate), although the best inducer is alanine. Measurement of the intracellular concentration of alanine showed that AldA contributes to net alanine synthesis in laboratory cultures. Divergently transcribed from aldA is an AsnC type regulator, aldR. Mutation of aldR prevents induction of AldA activity. Plasmid-borne gusA fusions showed that aldR is required for transcription of both aldA and aldR; hence, AldR is autoregulatory. However, plasmid fusions containing the aldA-aldR intergenic region could apparently titrate out AldR, sometimes resulting in a complete loss of AldA enzyme activity. Therefore, integrated aldR::gusA and aldA::gusA fusions, as well as Northern blotting, were used to confirm the induction of aldA activity. Both aldA and aldR were expressed in the II/III interzone and zone III of pea nodules. Overexpression of aldA in bacteroids did not alter the ability of pea plants to fix nitrogen, as measured by acetylene reduction, but caused a large reduction in the size and dry weight of plants. This suggests that overexpression of aldA impairs the ability of bacteroids to donate fixed nitrogen that the plant can productively assimilate. We propose that the role of AldA may be to balance the alanine level for optimal functioning of bacteroid metabolism rather than to synthesize alanine as the sole product of N-2 reduction.

Mutant alleles at the rugosus loci in pea affect seed moisture sorption isotherms and the relations between seed longevity and moisture content

Pea (Pisum sativum L.) mutant near-isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined in hermetic storage at 65 °C, also differed: longevity in the mutant near-isogenic lines was poorer and less sensitive to moisture content than in the wild type (i.e. CW was lower). The low-moisture-content limit (mc) to this relation also differed, being lower in the mutant near-isogenic lines (5.4–5.9%) than in the wild type (6.1%). In contrast, all four near-isogenic lines showed no difference (P >0.25) in the negative semi-logarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is concluded that the effect of these alleles at the r and rb loci on seed longevity was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption isotherms. However, this explanation could not be invoked at moisture contents below mc where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.

Genotype and temperature influence pea aphid resistance to a fungal entomopathogen

The influence of temperature on life history traits of four Acyrthosiphon pisum clones was investigated, together with their resistance to one genotype of the fungal entomopathogen Erynia neoaphidis . There was no difference among aphid clones in development rate, but they did differ in fecundity. Both development rate and fecundity were influenced by temperature, but all clones showed similar responses to the changes in temperature (i.e. the interaction term was nonsignificant). However, there were significant differences among clones in susceptibility to the pathogen, and this was influenced by temperature. Furthermore, the clones differed in how temperature influenced susceptibility, with susceptibility rankings changing with temperature. Two clones showed changes in susceptibility which mirrored changes in the in vitro vegetative growth rate of E. neoaphidis at different temperatures, whereas two other clones differed considerably from this expected response. Such interactions between genotype and temperature may help maintain heritable variation in aphid susceptibility to fungal pathogen attack and have implications for our understanding of disease dynamics in natural populations. This study also highlights the difficulties of drawing conclusions about the efficacy of a biological control agent when only a restricted range of pest genotypes or environmental conditions are considered.

Influence of temperature on pea aphid Acyrthosiphon pisum (Hemiptera: Aphididae) resistance to natural enemy attack

The ability to resist or avoid natural enemy attack is a critically important insect life history trait, yet little is understood of how these traits may be affected by temperature. This study investigated how different genotypes of the pea aphid Acyrthosiphon pisum Harris, a pest of leguminous crops, varied in resistance to three different natural enemies (a fungal pathogen, two species of parasitoid wasp and a coccinellid beetle), and whether expression of resistance was influenced by temperature. Substantial clonal variation in resistance to the three natural enemies was found. Temperature influenced the number of aphids succumbing to the fungal pathogen Erynia neoaphidis Remaudiere & Hermebert, with resistance increasing at higher temperatures (18 vs. 28degreesC). A temperature difference of 5degreesC (18 vs. 23degreesC) did not affect the ability of A. pisum to resist attack by the parasitoids Aphidius ervi Haliday and A. eadyi Stary Gonzalez & Hall. Escape behaviour from foraging coccinellid beetles (Hippodamia convergens Guerin-Meneville) was not directly influenced by aphid clone or temperature (16 vs. 21degreesC). However, there were significant interactions between clone and temperature (while most clones did not respond to temperature, one was less likely to escape at 16degreesC), and between aphid clone and ladybird presence (some clones showed greater changes in escape behaviour in response to the presence of foraging coccinellids than others). Therefore, while larger temperature differences may alter interactions between Acyrthosiphon pisum and an entomopathogen, there is little evidence to suggest that smaller changes in temperature will alter pea aphid-natural enemy interactions.

The competitive ability of pea-barley intercrops against weeds and the interactions with crop productivity and soil N availability

Grain legumes, such as peas (Pisum sativum L.), are known to be weak competitors against weeds when grown as the sole crop. In this study, the weed-suppression effect of pea–barley (Hordeum vulgare L.)intercropping compared to the respective sole crops was examined in organic field experiments across Western Europe (i.e., Denmark, the United Kingdom, France, Germany and Italy). Spring pea (P) and barley(B) were sown either as the sole crop, at the recommended plant density (P100 and B100, respectively), or in replacement (P50B50) or additive (P100B50)intercropping designs for three seasons (2003–2005). The weed biomass was three times higher under the pea sole crops than under both the intercrops and barley sole crops at maturity. The inclusion of joint experiments in several countries and various growing conditions showed that intercrops maintain a highly asymmetric competition over weeds, regardless of the particular weed infestation (species and productivity), the crop biomass or the soil nitrogen availability. The intercropping weed suppression was highly resilient, whereas the weed suppression in pea sole crops was lower and more variable. The pea–barley intercrops exhibited high levels of weed suppression, even with a low percentage of barley in the total biomass. Despite a reduced leaf area in the case of a low soil N availability, the barley sole crops and intercrops displayed high weed suppression, probably because of their strong competitive capability to absorb soil N. Higher soil N availabilities entailed increased leaf areas and competitive ability for light, which contributed to the overall competitive ability against weeds for all of the treatments. The contribution of the weeds in the total dry matter and soil N acquisition was higher in the pea sole crop than in the other treatments, in spite of the higher leaf areas in the pea crops.

Arabinose and protocatechuate catabolism genes are important for growth of Rhizobium leguminosarum biovar viciae in the pea rhizosphere

Background and aims: To form nitrogen-fixing nodules on pea roots, Rhizobium leguminosarum biovar viciae must be competitive in the rhizosphere. Our aim was to identify genes important for rhizosphere fitness. Methods: Signature-tagged mutants were screened using microarrays to identify mutants reduced for growth in pea rhizospheres. Candidate mutants were assessed relative to controls for growth in minimal medium, growth in pea rhizospheres and for infection of peas in mixed inoculants. Mutated genes were identified by DNA sequencing and confirmed by transduction. Results: Of 5508 signature-tagged mutants, microarrays implicated 50 as having decreased rhizosphere fitness. Growth tests identified six mutants with rhizosphere-specific phenotypes. The mutation in one of the genes (araE) was in an arabinose catabolism operon and blocked growth on arabinose. The mutation in another gene (pcaM), encoding a predicted solute binding protein for protocatechuate and hydroxybenzoate uptake, decreased growth on protocatechuate. Both mutants were decreased for nodule infection competitiveness with mixed inoculants, but nodulated peas normally when inoculated alone. Other mutants with similar phenotypes had mutations predicted to affect secondary metabolism. Conclusions: Catabolism of arabinose and protocatechuate in the pea rhizosphere is important for competitiveness of R.l. viciae. Other genes predicted to be involved in secondary metabolism are also important.

Adaptation of Rhizobium leguminosarum to pea, alfalfa and sugar beet rhizospheres investigated by comparative transcriptomics

Background The rhizosphere is the microbe-rich zone around plant roots and is a key determinant of the biosphere's productivity. Comparative transcriptomics was used to investigate general and plant-specific adaptations during rhizosphere colonization. Rhizobium leguminosarum biovar viciae was grown in the rhizospheres of pea (its legume nodulation host), alfalfa (a non-host legume) and sugar beet (non-legume). Gene expression data were compared to metabolic and transportome maps to understand adaptation to the rhizosphere. Results Carbon metabolism was dominated by organic acids, with a strong bias towards aromatic amino acids, C1 and C2 compounds. This was confirmed by induction of the glyoxylate cycle required for C2 metabolism and gluconeogenesis in all rhizospheres. Gluconeogenesis is repressed in R. leguminosarum by sugars, suggesting that although numerous sugar and putative complex carbohydrate transport systems are induced in the rhizosphere, they are less important carbon sources than organic acids. A common core of rhizosphere-induced genes was identified, of which 66% are of unknown function. Many genes were induced in the rhizosphere of the legumes, but not sugar beet, and several were plant specific. The plasmid pRL8 can be considered pea rhizosphere specific, enabling adaptation of R. leguminosarum to its host. Mutation of many of the up-regulated genes reduced competitiveness for pea rhizosphere colonization, while two genes specifically up-regulated in the pea rhizosphere reduced colonization of the pea but not alfalfa rhizosphere. Conclusions Comparative transcriptome analysis has enabled differentiation between factors conserved across plants for rhizosphere colonization as well as identification of exquisite specific adaptation to host plants.

Differential uptake, partitioning and transfer of Cd and Zn in the soil-pea plant-aphid system

The biomagnification of trace metals during transfer from contaminated soil to higher trophic levels may potentially result in the exposure of predatory arthropods to toxic concentrations of these elements. This study examined the transfer of Cd and Zn in a soil−plant−arthropod system grown in series of field plots that had received two annual applications of municipal biosolids with elevated levels of Cd and Zn. Results showed that biosolids amendment significantly increased the concentration of Cd in the soil and the shoots of pea plants and the concentration of Zn in the soil, pea roots, shoots, and pods. In addition, the ratio of Cd to Zn concentration showed that Zn was preferentially transferred compared to Cd through all parts of the system. As a consequence, Zn was biomagnified by the system whereas Cd was biominimized. Cd and Zn are considered to exhibit similar behaviors in biological systems. However, the Cd/Zn ratios demonstrated that in this system, Cd is much less labile in the root−shoot−pod and shoot−aphid pathways than Zn.

Peça por peça: sistematização de um programa de responsabilidade social

O objetivo da dissertação foi analisar o processo de desenvolvimento e a aplicação de ações sociais e trabalho voluntário, que demonstram a preocupação da empresa com o seu papel social, através de uma participação mais ativa, concreta e efetiva, influenciando na ocorrência das mudanças que a sociedade necessita. O foco do estudo foi analisar um dessas empresas, notadamente a Robert Bosch Limitada, de capital alemão, radicada no Brasil desde o início da década de 1950. Sendo considerada, mais especificamente, uma de suas unidades, localizada no Paraná desde 1975. A Bosch Curitiba, através da implementação de um programa de ação social baseado principalmente na educação e no desenvolvimento sustentável, pretendeu criar condições para que a comunidade de um bairro da periferia de Curitiba pudesse identificar oportunidades de desenvolvimento econômico e social. Esta dissertação é o resultado dessa discussão e se desenvolveu por meio de um programa de ação social que evidencia a importância da participação ativa da empresa na comunidade, baseada em projetos que evidenciam a educação como a essência para o desenvolvimento social. A Vila Verde, comunidade da periferia de Curitiba, foi escolhida pela empresa para implantar o programa de responsabilidade social (Peça por Peça). Nessa comunidade, o foco principal foram os membros da faixa etária de O a 18 anos. O programa, portanto, teve a participação de uma empresa, dos seus colaboradores, como voluntários, e das escolas da comunidade envolvida. A coleta dos dados deu-se por diferentes procedimentos: pesquisa bibliográfica, pesquisa documental, observação participante e entrevistas. Os dados qualitativos foram comparados, e foram apresentados em forma de relatório. Os dados quantitativos foram tabulados e avaliados, servindo de apoio e confirmação aos resultados apresentados pela análise dos dados quantitativos. A atuação do programa social, Peça por Peça, foi no sentido de sensibilizar, estimular e criar condições de conscientizar os envolvidos que as mudanças necessárias somente serão efetivas na medida em que aumentar o seu nível de comprometimento, ou seja, tomar-se uma população capaz de se organizar e de preservar e defender seus interesses e anseios, desenvolvendo seu papel natural do exercício da cidadania e de uma convivência social que assegure direitos básicos para qualquer processo e evolução de uma sociedade. Sistematizar um programa de responsabilidade social, mais do que pretender criar soluções inovadoras, busca consolidar um outro pressuposto, em que a maioria das atividades sociais implementadas, sejam elas de cunho filantrópico ou não, dificilmente conseguem se manter e alegando várias razões, mas de que alguma forma sempre se reflete na falta de uma sistemática de trabalho, com metas, monitoramento, resultados esperados, com um planejamento estratégico que projete as ações a curto, médio e longo prazo. Isso também é uma evidência de que um projeto social não direcionado para atividades assistencialistas, mas sim para a busca de exercer efetivamente a responsabilidade social, não deve ter no fator tempo a principal referência de sucesso do empreendimento, mas sim de pequenas ações de melhoria de forma continuada e planejada, auto-sustentada, efetiva, mensurável e compartilhada.

Uma investigação das relações familiares na peça "Do Fundo do Lago Escuro (Assunto de Família)", de Domingos de Oliveira

A partir de três conceitos fundamentais para a compreensão da dinâmica das relações familiares: a pseudo-mutualidade, elaborada por Wynne, nos Estados Unidos, o postulado fusional, desenvolvido por Hochmann, na França e a mistificação, por Laing, na Inglaterra, investigou-se a estrutura de relações familiares em um texto teatral brasileiro, atual, "Do Fundo do Lago Escuro", de Domingos de Oliveira. Os três conceitos acima citados, fundamentais para a compreensão da dinâmica das relações familiares dentro de uma perspectiva sistêmica (não-psicanalítica),estão interrelacionados entre si e surgiram apartir de estudos realizados com famílias com um membro esquizofrênico, em três diferentes paises. Buscou-se estabelecer os pontos de contato, as divergências metodológicas, teóricas e ideológicas e os aspectos complementares dos referidos conceitos, bem como verificar sua aplicabilidade a uma estrutura familiar considerada representativa de certa parcela da sociedade brasileira, em determinada ocasião. Concluiu-se pela aplicabilidade dos conceitos, desenvolvidos em três diferentes países, a uma dada estrutura familiar brasileira em um dado momento histórico, e pela aplicabilidade dos conceitos a um grupo familiar que não apresenta, através de qualquer de seus membros, um quadro esquizofrênico manifesto.

O corpo tornado voz : a experiência pedagógica da peça radiofônica

Este trabalho apresenta o rádio, mais especificamente a peça radiofônica, como uma experiência pedagógica para atores que assim ampliam seu repertório e tornam a voz protagonista da ação. Entendendo a linguagem radiofônica como linguagem artística e o rádio como um meio expressivo, o estudo pretende um conhecimento vocal voltado para o efeito da voz, sua dimensão temporal e espacial e o estatuto de corpo que ela assume nessas condições. Traz a perspectiva da pedagogia do ator, considerando o ouvinte como interlocutor, sem o que a ação do ator não se concretiza. Utiliza como objeto de pesquisa, a investigação O trabalho do ator voltado para um veículo radiofônico, realizada no âmbito do Departamento de Arte Dramática, Instituto de Artes da Universidade Federal do Rio Grande do Sul, e busca sistematizar para o exercício radiofônico as práticas desenvolvidas pelos atores em seu processo de criação. Para tanto, articula diálogos com as vozes e idéias de Rudolf Arnheim, Werner Klippert, Eduardo Meditsch, Constantin Stanislavski, João Francisco Duarte Junior e Jorge Larrosa, entre outros. Como desdobramento, mostra a possibilidade de promover a oralidade e o exercício radiofônico como expressões individuais e como experiências criativas coletivas e pedagógicas, em atividades para a sala de aula em todos os níveis de ensino, para a oficina e para a ação cultural. Demarca, ainda, a busca por uma expressão radiofônica contemporânea, uma linguagem que faça sentido hoje, abrindo espaço para a escuta ainda que num mundo coberto de imagens.

Improvisação na música contemporânea de concerto : parâmetros para execução da cadenza da peça "The days fly by" de Frederic Rzewski

A presente pesquisa apresenta uma proposta de treinamento para a improvisação de uma cadenza na peça “The Days Fly By” de Frederick Rzewski. A improvisação é um aspecto que se manifesta de várias maneiras no trabalho e na trajetória deste compositor, sendo ele próprio pianista reconhecido por seus improvisos de cadenzas em concertos tradicionais. Seu processo de composição está intimamente relacionado ao da improvisação. É comum em suas composições a inclusão de uma seção em aberto para ser improvisada pelo intérprete. Utilizo os conceitos de referente, base de conhecimento de Jeff Pressing e ponto de partida de Bruno Nettl associados a um modelo de aprendizagem da improvisação proposto por Barry J. Kenny & Martin Gellrich. Esta pesquisa apresenta proposta de exercícios de improvisação fundamentados nos elementos detectados em uma análise da peça.

Peça para caixa clara

O professor realiza a execução de uma peça para caixa clara, de modo a demonstrar aos alunos sua execução correta.