Two component systems: physiological effect of a third component

Signal transduction systems mediate the response and adaptation of organisms to environmental changes. In prokaryotes, this signal transduction is often done through Two Component Systems (TCS). These TCS are phosphotransfer protein cascades, and in their prototypical form they are composed by a kinase that senses the environmental signals (SK) and by a response regulator (RR) that regulates the cellular response. This basic motif can be modified by the addition of a third protein that interacts either with the SK or the RR in a way that could change the dynamic response of the TCS module. In this work we aim at understanding the effect of such an additional protein (which we call ‘‘third component’’) on the functional properties of a prototypical TCS. To do so we build mathematical models of TCS with alternative designs for their interaction with that third component. These mathematical models are analyzed in order to identify the differences in dynamic behavior inherent to each design, with respect to functionally relevant properties such as sensitivity to changes in either the parameter values or the molecular concentrations, temporal responsiveness, possibility of multiple steady states, or stochastic fluctuations in the system. The differences are then correlated to the physiological requirements that impinge on the functioning of the TCS. This analysis sheds light on both, the dynamic behavior of synthetically designed TCS, and the conditions under which natural selection might favor each of the designs. We find that a third component that modulates SK activity increases the parameter space where a bistable response of the TCS module to signals is possible, if SK is monofunctional, but decreases it when the SK is bifunctional. The presence of a third component that modulates RR activity decreases the parameter space where a bistable response of the TCS module to signals is possible.

Investigação da toxicidade reprodutiva do fungicida Procloraz, com ênfase sobre aspectos morfofuncionais do epidídimo de ratos adultos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fungicidas de efeitos fisiológicos no desenvolvimento de plantas de pimentão enxertadas e não enxertadas sob cultivo protegido

Pós-graduação em Agronomia (Horticultura) - FCA

Participação das NETs (neutrophil extracellular traps) na atividade fungicida de neutrófilos humanos contra o Paracoccidioides brasiliensis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aplicação de produtos de efeitos fisiológicos na pro- dução de brócolis tipo ramoso

Pós-graduação em Agronomia (Horticultura) - FCA

Fungicidas de efeitos fisiológicos no metabolismo e desenvolvimento de plantas de melão rendilhado sob cultivo protegido

Pós-graduação em Agronomia (Horticultura) - FCA

Effect of diurnal cycling temperatures on cardiovascular- ventilatory function in statically-acclimated rainbow trout, Salmo gairdneri

Four groups of rainbow trout, Salmo gairdneri, were acclimated to 2°, 10°, and 18°e, and to a diurnal temperature cycle (100 ± 4°C). To evaluate the influence of cycling temperatures in terms of an immediate as opposed to acclimatory response various ventilatory-cardiovascular rate functions were observed for trout, either acclimated to cycling temperatures or acclimated to constant temperatures and exposed to a diurnal temperature cycle for the first time (10° ± 4°C for trout acclimated to 10°C; 18°+ 4°C for trout acclimated to l8°e). Gill resistance and the cardiac to ventilatory rate ratio were then calculated. Following a post preparatory recovery period of 36 hr, measurements were made over a 48 hour period with the first 24 hours being at constant temperature in the case of statically-acclimated fish followed by 24 hours under cyclic temperature conditions. Trout exhibited marked changes in oxygen consumption (Vo ) with temp- 2 erature both between acclimation groups, and in response to the diurnal temperature cycle. This increase in oxygen uptake appears to have been achieved by adjustment of ventilatory and, to some extent, cardiovascular activity. Trout exhibited significant changes in ventilatory rate (VR), stroke volume (Vsv), and flow (VG) in response to temperature. Marked changes in cardiac rate were also observed. These findings are discussed in relation to their importance in convective oxygen transport via water and blood at the gills and tissues. Trout also exhibited marked changes in pressure waveforms associated with the action of the resp; ratory pumps with temperature. Mean differenti a 1 pressure increased with temperature as did gill resistance and utilization. This data is discussed in relation to its importance in diffusive oxygen transport and the conditions for gas exchange at the gills. With one exception, rainbow trout were able to respond to changes in oxygen demand and availability associated with changes in temperature by means of adjustments in ventilation, and possibly pafusion, and the conditions for gas exchange at the gills. Trout acclimated to 18°C, however, and exposed to high cyclic temperatures, showed signs of the ventilatory and cardiovascular distress problems commonly associated with low circulating levels of oxygen in the blood. It appears these trout were unable to fully meet the oxygen requirements associated with c~ling temperatures above 18°C. These findings were discussed in relation to possible limitations in the cardiovascular-ventilatory response at high temperatures. The response of trout acclimated to cycling temperatures was generally similar to that for trout acclimated to constant temperatures and exposed to cycling temperatures for the first time. This result suggested that both groups of fish may have been acclimated to a similar thermal range, regardless of the acclimation regime employed. Such a phenomenon would allow trout of either acclimation group to respond equally well to the imposed temperature cycle. Rainbow trout showed no evidence of significant diurnal rhythm in any parameters observed at constant temperatures (2°, 10°, and 18° C), and under a 12/12 light-dark photoperiod regime. This was not taken to indicate an absence of circadian rhythms in these trout, but rather a deficiency in the recording methods used in the study.

Efeito do manejo cultural e químico na incidência e severidade da mancha-preta dos citros

A citricultura apresenta vários problemas fitossanitários, dentre os quais a mancha-preta dos citros (Guignardia citricarpa). O controle desta doença baseia-se no emprego de práticas culturais e no uso de fungicidas. Avaliou-se o efeito do manejo do mato em conjunto com o químico no controle da doença. Os experimentos foram instalados em pomares de laranjeiras-doces, nos municípios de Matão, Rio Claro e Mogi Guaçu, no Estado de São Paulo. No manejo do mato, comparou-se o uso isolado de roçadeira ecológica com o conjugado rastelo mecânico e trincha, aos 35 dias, após 2/3 de pétalas caídas. No controle químico, foram realizadas duas pulverizações com fungicida protetor e de 2 a 5 pulverizações da mistura de produto sistêmico com protetor, aos 45 dias, após 2/3 de pétalas caídas, em intervalos de aplicação de 35 dias. em todas as aplicações, foi adicionado óleo mineral emulsionável (0,25%). Avaliou-se a área abaixo da curva de progresso da incidência e severidade da doença, com os dados de cinco avaliações realizadas quinzenalmente, a partir da maturidade fisiológica dos frutos. em todas as áreas, o uso do controle químico, associado com o manejo do mato, reduziu a intensidade da doença.

Efeitos fisiológicos de fungicidas no desenvolvimento de plantas de melão rendilhado, cultivadas em ambiente protegido

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

População de plantas e uso de piraclostrobina na cultura do milho: alterações agronômicas e fisiológicas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sensitivity of Colletotrichum lindemuthianum from green beans to fungicides and race determination of isolates from State of Sao Paulo, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Expression and characterization of glycogen synthase kinase-3 mutants and their effect on glycogen synthase activity in intact cells.

In these studies we expressed and characterized wild-type (WT) GSK-3 (glycogen synthase kinase-3) and its mutants, and examined their physiological effect on glycogen synthase activity. The GSK-3 mutants included mutation at serine-9 either to alanine (S9A) or glutamic acid (S9E) and an inactive mutant, K85,86MA. Expression of WT and the various mutants in a cell-free system indicated that S9A and S9E exhibit increased kinase activity as compared with WT. Subsequently, 293 cells were transiently transfected with WT GSK-3 and mutants. Cells expressing the S9A mutant exhibited higher kinase activity (2.6-fold of control cells) as compared with cells expressing WT and S9E (1.8- and 2.0-fold, respectively, of control cells). Combined, these results suggest serine-9 as a key regulatory site of GSK-3 inactivation, and indicate that glutamic acid cannot mimic the function of the phosphorylated residue. The GSK-3-expressing cell system enabled us to examine whether GSK-3 can induce changes in the endogenous glycogen synthase activity. A decrease in glycogen synthase activity (50%) was observed in cells expressing the S9A mutant. Similarly, glycogen synthase activity was suppressed in cells expressing WT and the S9E mutant (20-30%, respectively). These studies indicate that activation of GSK-3 is sufficient to inhibit glycogen synthase in intact cells, and provide evidence supporting a physiological role for GSK-3 in regulating glycogen synthase and glycogen metabolism.

Compatibilidade entre tratamentos químico e biológico de sementes de feijão para controle de Fusarium oxysporum f. sp. phaseoli

Atualmente, a produtividade do feijoeiro comum (Phaseolus vulgaris L.) pode ser reduzida devido à ocorrência de doenças em todo o território nacional, destacando-se a murcha de fusário, causada por Fusarium oxysporum f. sp. phaseoli (Fop). No campo, o patógeno é disseminado a longas distâncias através das sementes infectadas e/ou contaminadas e a sua sobrevivência ocorre, principalmente, no solo. Os objetivos deste trabalho foram: avaliar a inibição do crescimento micelial de Fop por Trichoderma spp.; classificar a sensibilidade in vitro de Fop e Trichoderma spp., separadamente, a fungicidas e verificar a compatibilidade entre fungicidas químicos e biológicos para controle de Fop, presente nas sementes e no solo. Para avaliar a inibição do crescimento micelial de Fop, foram utilizados três isolados do patógeno, os quais foram confrontados, in vitro, com três isolados de Trichoderma spp. em testes de cultura pareada e produção de metabólitos voláteis a 20-22°C. Os experimentos foram conduzidos em delineamento inteiramente casualizado, com cinco repetições para cada isolado de Trichoderma. Para a classificação da sensibilidade in vitro de Fop e Trichoderma a fungicidas, foram avaliados os mesmos isolados anteriormente utilizados. Foram comparados dez fungicidas, em doses entre 0 a 100 mg L-1 que foram ajustadas de acordo com a CI50 de cada fungicida. Com base na percentagem de inibição do crescimento micelial, foram estimados os valores da concentração inibitória de 50% (CI50) e 100% (CI100) e selecionaram-se os fungicidas compatíveis com Trichoderma spp. A compatibilidade entre tratamentos químico e biológico foi avaliada através da inoculação artificial de sementes de feijão com um isolado de Fop (IAC 11.299-1) e infestação do mesmo no solo. As sementes foram tratadas com os fungicidas fludioxonil, flutriafol e tiofanato metílico, e com os três produtos biológicos, separadamente e em misturas. Avaliou-se o efeito dos tratamentos por meio dos testes de sanidade, germinação, comprimento de plântulas, massa da matéria seca em laboratório e índice de velocidade de emergência e porcentagem de emergência em estufa não climatizada. O efeito protetor dos tratamentos foi verificado através do teste de transmissão do patógeno solo-planta. Todos os isolados de Trichoderma apresentaram antagonismo in vitro contra Fop. No teste de cultura pareada foi observada uma redução de 15 a 20% no crescimento micelial do patógeno. No teste de produção de metabólitos voláteis, o isolado T12-1086G05 foi responsável pela maior inibição do crescimento micelial de Fop (10 a 48%). Os testes de sensibilidade in vitro mostraram que tiofanato metílico, flutriafol e fludioxonil foram compatíveis com Trichoderma (CI50 > 2 mg L-1). Com exceção do flutriafol e do GF 422 isolados e em mistura, todos os tratamentos foram eficientes na erradicação de Fop nas sementes, sem afetar a sua qualidade fisiológica. No teste de transmissão, verificou-se que a incidência de Fop foi de 5 a 40% no hipocótilo e de 5 a 30% nas raízes de feijoeiro provenientes de sementes tratadas com os produtos.

Physiological energetics of the thick shell mussel Mytilus coruscus exposed to seawater acidification and thermal stress

Anthropogenic CO2 emissions have caused seawater temperature elevation and ocean acidification. In view of both phenomena are occurring simultaneously, their combined effects on marine species must be experimentally evaluated. The purpose of this study was to estimate the combined effects of seawater acidification and temperature increase on the energy budget of the thick shell mussel Mytilus coruscus. Juvenile mussels were exposed to six combined treatments with three pH levels (8.1, 7.7 and 7.3) * two temperatures (25 °C and 30 °C) for 14 d. We found that clearance rates (CRs), food absorption efficiencies (AEs), respiration rates (RRs), ammonium excretion rates (ER), scope for growth (SFG) and O:N ratios were significantly reduced by elevated temperature sometimes during the whole experiments. Low pH showed significant negative effects on RR and ER, and significantly increased O:N ratios, but showed almost no effects on CR, AE and SFG of M. coruscus. Nevertheless, their interactive effects were observed in RR, ER and O:N ratios. PCA revealed positive relationships among most physiological indicators, especially between SFG and CR under normal temperatures compared to high temperatures. PCA also showed that the high RR was closely correlated to an increasing ER with increasing pH levels. These results suggest that physiological energetics of juvenile M. coruscus are able to acclimate to CO2 acidification with a little physiological effect, but not increased temperatures. Therefore, the negative effects of a temperature increase could potentially impact the ecophysiological responses of M. coruscus and have significant ecological consequences, mainly in those habitats where this species is dominant in terms of abundance and biomass.