The N'-terminal domain of glyceraldehyde-3-phosphate dehydrogenase of the apicomplexan Plasmodium falciparum mediates GTPase Rab2-dependent recruitment to membranes.

Spatial and temporal distribution of the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase (pfGAPDH) and aldolase (pfAldolase) of Plasmodium falciparum were investigated using specific mAbs and indirect immunofluorescence analysis (IFA). Both glycolytic enzymes were co-localized during ring and trophozoite stages of both liver and asexual blood stage parasites. During schizogony, pfGAPDH became associated with the periphery of the parasites and eventually accumulated in the apical region of merozoites, while pfAldolase showed no segregation. Subcellular fractionation experiments demonstrated that pfGAPDH was found in both the membrane-containing pellet and the supernatant fraction of parasite lysates. In contrast, pfAldolase was only found in the supernatant fraction. A quantitative binding assay showed that pfGAPDH could be recruited to HeLa cell microsomal membranes in response to mammalian GTPase Rab2, indicating that Rab2-dependent recruitment of cytosolic components to membranes is conserved in evolution. Two overlapping fragments of pfGAPDH (residues 1-192 and 133-337) were evaluated in the microsomal binding assay. We found that the N'-terminal fragment competitively inhibited Rab2-stimulated pfGAPDH recruitment. Thus, the domain mediating the evolutionarily conserved Rab2-dependent membrane recruitment is located in the N'-terminus of GAPDH. Together, these results suggest that pfGAPDH exerts non-glycolytic function(s) in P. falciparum, possibly including a role in vesicular transport and biogenesis of apical organelles

A Ypt32p Exchange Factor Is a Putative Effector of Ypt1p

Ypt1p regulates vesicle tethering and fusion events from the ER to the Golgi and through the early Golgi. Genetic studies have suggested a functional relationship between Ypt1p and Ypt31p/Ypt32p. Ypt31p and Ypt32p are a pair of functionally redundant GTPases that act after Ypt1p to mediate intra-Golgi traffic or the budding of post-Golgi vesicles from the trans-Golgi. Here we report that a novel Ypt32p exchange factor is a putative effector of Ypt1p. These findings implicate small GTP-binding proteins of the Ypt/Rab family in a signal cascade that directs membrane traffic through the secretory pathway

Efeito da adubação alternativa do maracujazeiro-amarelo nas características químicas e físicas do solo Alternative manuring of the yellow passion fruit plant: effects on chemical and physical characteristics of the soil

Adubações minerais e orgânicas promovem alterações nas condições físicas e químicas do solo, com conseqüente efeito na produtividade das culturas. Um experimento foi realizado no Município de Campos dos Goytacazes, RJ, de fevereiro de 2005 a julho de 2006, para comparar diferentes adubos orgânicos com a adubação mineral do maracujazeiro-amarelo quanto aos efeitos sobre as características químicas e físicas do solo adubado. O delineamento experimental foi em blocos casualizados, com quatro repetições e seis tratamentos, correspondentes às seguintes adubações por planta: (AM) adubação mineral = 100 g da fórmula NPK 20-5-20 + cobertura morta (CM); EB = 5 L de esterco bovino + CM; FOC = 500 g de farinha de ossos e carne + CM; RM = 5 L de raspa de mandioca + CM; TF C/CM = 5 L de torta de filtro + CM; TF S/CM = 5 L de torta de filtro - sem CM. A adubação mineral foi feita a cada 30 dias e as adubações orgânicas a cada 60 dias. Foram avaliados os atributos químicos: pH, condutividade elétrica, teores de P, K, Ca, Mg, Na, Al, H + Al, e matéria orgânica; e os físicos: granulometria, densidade do solo e das partículas, porosidade total, macro e microporosidade, capacidade de campo, ponto de murcha e água disponível em três diferentes profundidades (0-5, 5-10, 10-15 cm). Os adubos orgânicos aplicados no maracujazeiro promoveram mudanças significativas nas características químicas do solo, em comparação com a adubação mineral tradicional, em que houve aumento do pH e do H + Al em todas as profundidades, e redução dos teores de Al nas camadas mais profundas. Houve, ainda, aumento nos teores de nutrientes no solo e, por conseqüência, na soma de bases, principalmente na camada superior, sendo a torta de filtro o composto orgânico mais eficiente em promover tais melhorias, inclusive aumentando a CTC do solo. Apenas a torta de filtro promoveu alterações nas características físicas do solo, reduzindo as quantidades de areia grossa e aumentando as quantidades de silte, argila e matéria orgânica. As demais características físicas do solo não foram influenciadas pela adição de adubos orgânicos no maracujazeiro, em comparação com a adubação mineral tradicional.<br>The supply of mineral and organic manuring promotes alterations in the physical and chemical conditions of the soil, with consequent effects on crop productivity. An experiment was accomplished in the county of Campos dos Goytacazes, RJ, from February 2004 to July 2006, to compare different organic fertilizers with the traditional chemical manuring of the yellow passion fruit plant regarding their effects on chemical and physical characteristics of the fertilized soil. The experiment had a randomized complete block design with four replicates, with six treatments of fertilizer levels per plant as follows: (AQ) Chemical manuring = 100 g of the formula 20-5-20 (N-P2O5-K2O) + mulching (CM); EB = 5 L of bovine manure + CM; FOC = 500 g of bone and meat flour + CM; RM = 5 L of cassava abrades + CM; TF + CM = 5 L of sugar cane plant filter pie + CM; TF = 5 L of sugar cane filter pie without CM. Chemical manuring was done every 30 days, while organic manuring every 60 days. The soil chemical characteristics (pH, electric conductivity, levels of P, K, Ca, Mg, Na Al, H + Al, and organic matter) and physical characteristics (granulometry, density of the soil and of the particles, total porosity, macro and microporosity, field capacity, wilting point and water availability) were determined in 0-5, 5-10, 10-15 cm soil layers. The organic fertilizers applied to passion fruit plant modified significantly the soil chemical characteristics, in comparison to the traditional chemical manuring, increasing pH and H + Al in all soil depths, and reducing Al availability in the deepest layers. There was also an increase in the availability of nutrients in the soil and so in the sum of bases, mainly in the surface layer, the filter pie being the most efficient organic manure in promoting such improvements, besides increasing soil CTC. Only the filter pie modified the soil physical characteristics, reducing the amounts of coarse sand and increasing the amounts of silt, clay and organic matter. The other physical characteristics of the soil were not influenced by the addition of organic fertilizers to the passion fruit plant, in comparison with the traditional chemical fertilizers

Mineralização de carbono e de nitrogênio provenientes de composto de lixo urbano em argissolo Carbon and nitrogen mineralization in an ultisol fertilized with urban waste compost

Estudos da mineralização do C e do N em solos que receberam aplicação de composto de lixo urbano são importantes para avaliar o comportamento desse resíduo no solo e dar subsídios para definir as doses adequadas às culturas, com vistas em atender à necessidade de N das plantas. Foram realizados dois experimentos em condições de laboratório com o objetivo de avaliar a mineralização de C e de N em um Argissolo textura média adubado com composto de lixo urbano. No primeiro experimento, utilizou-se delineamento inteiramente ao acaso, com cinco tratamentos e três repetições, com os tratamentos constituídos de cinco doses de composto de lixo urbano, equivalentes a 0, 30, 60, 90 e 120 t ha-1. No segundo experimento, empregou-se esquema fatorial, com delineamento inteiramente ao acaso e três repetições, combinando as mesmas cinco doses de composto de lixo urbano utilizadas no primeiro experimento e 11 tempos de incubação (0, 7, 14, 28, 42, 56, 70, 84, 98, 112 e 126 dias). Os maiores aumentos de N-NO3- no solo foram obtidos até os 42 dias de incubação, independentemente da dose de composto de lixo aplicada, percebendo-se, a partir dos 70 dias, tendência de estabilização. A fração de mineralização de C-orgânico em C-CO2 menor do que 2 % em 168 dias indica que o composto de lixo urbano é material que contribui para aumentar os estoques de matéria orgânica do solo. Na ausência de adubação nitrogenada complementar, a fração de mineralização de N-orgânico de 12 % em 126 dias evidencia que o composto de lixo urbano apresenta potencial fertilizante de liberação lenta de N para as plantas.<br>Studies about nitrogen and carbon mineralization in soils amended with urban waste compost are important to evaluate the reactions of this waste in soil and to define the best rates for crops. Two experiments were carried out under laboratory conditions to evaluate carbon and nitrogen mineralization in an Ultisol fertilized with urban waste compost. The Ultisol first experiment had a completely randomized design, with five urban waste compost rates of 0, 30, 60, 90, and 120 t ha-1 and three replicates. In the second experiment, N mineralization was evaluated at the same waste compost rates along eleven incubation periods (0, 7, 14, 28, 42, 56, 70, 84, 98, 112, and 126 days), in three replicates. The following results were obtained for a medium texture Ultisol fertilized with urban waste compost: regardless of urban waste compost dose the greatest increase in N-NO3- in the soil was found up to 42 days, stabilizing afterwards; the mineralization rate of organic carbon of less than 2 % in 168 days indicates that urban waste compost contributes to increase soil organic matter. In the absence of other N fertilizers, urban waste compost releases N to plants slowly at a rate of 12 % in 126 days, demonstrating its potential as slow-release nitrogen fertilizer