Search

Wheat straw, one of the most abundant agricultural residues worldwide, can be used to produce biogas, which is considered one of the most efficiently produced renewable energies. Wheat grown with the dual-purpose of producing food and biogas should display simultaneously high grain and straw yields, low lodging susceptibility and high conversion efficiency of straw into biogas. The aims of this study were to determine the best food-fuel dual-purpose wheat candidates among 36 wheat genotypes—including French, CIMMYT and local (Criollo) germplasm—used in breeding programs in Argentina and to gain some insights into the relationships between key traits relevant for dual-purpose wheat genotypes. Results High variability in individual key traits for dual-purpose wheat ideotype has been found. Genotypes of French origin displayed the highest grain yield, and those of CIMMYT origin, the lowest straw yield. Genotypes of Criollo origin showed the highest lodging susceptibility, and French ones, the lowest. Straw yield was positively correlated with grain yield in all genotypes, and negatively correlated with plant height in genotypes of Criollo origin. Straw conversion into biogas was measured in terms of the biogas potential production and kinetic parameters Bmax (maximum specific biogas production) and k (first-order kinetic constant) were analyzed. All key traits were analyzed together by a principal component analysis. Baguette 31 and SNR Nogal, two genotypes of French origin, showed high grain yield, high-to-very high straw yield, low lodging susceptibility, and moderate-to-high Bmax and k. Buck Guapo and Buck Baqueano, two genotypes of Criollo origin, displayed good values for grain yield, straw yield and Bmax and k. However, their high lodging susceptibility precludes their production in shallow soils or high-input systems. Lastly, some old genotypes (e.g. Klein Atlas) harbored a good combination of all key traits and could prove valuable to be included in future breeding programs for dual-purpose wheat. Conclusions While none of the genotypes excelled in every key trait, a few candidates showed potential for dual-purpose ideotype, particularly Baguette 31 and SNR Nogal. The challenge lays in gathering all attributes for food and 2G fuel in the same genotype. EEA Balcarce Fil: Gabbanelli, Nadia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina. Fil: Gabbanelli, Nadia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Fil: Erbetta, Elisa. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina. Fil: Erbetta, Elisa. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Fil: Sanz Smachetti, Maria Eugenia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina. Fil: Sanz Smachetti, Maria Eugenia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Fil: Lorenzo, Máximo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Fil: Lorenzo, Máximo. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Fil: Talia, Paola Mónica. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Agrobiotecnología y Biología Molecular; Argentina. Fil: Ramírez, Ignacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Fil: Ramírez, Ignacio. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Fil: Vera, Magdalena. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Fil: Vera, Magdalena. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Fil: Durruty, Ignacio. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina. Fil: Pontaroli, Ana Clara. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina. Fil: Pontaroli, Ana Clara. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Fil: Echarte, María Mercedes. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina. Fil: Echarte, María Mercedes. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina.

High oleic hybrids of sunflower are widely cultivated around the world. The effect of temperature on oleic acid percentage of these hybrids is a concern, since oils with oleic acid percentage above a threshold receive a prime over the regular price. The objective of this work was to identify the main avenues for the genetic improvement of oleic acid percentage of high oleic hybrids of sunflower, both in current and future global warming scenarios. A data set obtained in a trial network allowed to explore the oleic acid percentage response to temperature of high oleic hybrids in the argentine sunflower growing region (between 29 and 38° LS, 46 trials in 15 locations during the period 2005/06–2012/2013). A similar data set was used to evaluate the variability in phenology. Mean values and stability across environments of oleic acid percentage differed among the studied high oleic hybrids. Differences in the parameter values of a sigmoid equation evidenced the variability in the response of oleic acid to temperature. Oleic acid percentage was simulated with a model that included this equation coupled to a phenology module, for different sowing dates and locations with contrasting temperature, under current conditions and a global warming scenario. It was possible to identify a low number of temperatures and field environments useful to reproduce the rankings of hybrids obtained with a wide range of temperatures. This information could be used to phenotype for high oleic percentage with a low number of experiments and reduce the efforts to identify better high oleic genotypes. Simulations show that the maximum oleic acid percentage is currently not attained in 50% of the studied hybrids in some sowing dates, even at the warmest locations, while in a future global warming scenario it would not be attained in 30% of the studied hybrids in the colder locations. Sensitivity analysis was performed for parameters of the sigmoid equation and the phenology module determining when the critical period for fatty acid composition occurs. In both in current and future scenarios, phenology parameters showed a null or low effect on oleic acid percentage. Two parameters of the sigmoid equation showed a significant impact, which differed between current and future scenarios. Simulations suggest that the stability of oleic acid percentage could still be a concern in the future. However, selecting for key parameter values for a given scenario could help to obtain better high oleic hybrids of sunflower.

Most of the studies addressing the influence of management practices on seasonal crop water use efficiency (i.e., the ratio between shoot biomass and evapotranspiration in a seasonal scale, WUE(B, ET, s)) have focused on their effect on evaporation. Processes specifically related to the crop transpiration component received less attention as possible mechanisms underlying WUE(B, ET, s) responses. In this study, we provide empirical evidence in support to theoretical predictions on how agronomic management practices such as N supply or plant density changes modify maize (Zea mays L.) transpiration efficiency for shoot biomass production (i.e., the ratio between shoot biomass and transpiration in a seasonal scale, WUE(B, T, s)); and determine the contribution of crop conductance (gc) and radiation use efficiency (RUEB) to the response of WUE(B, T, s) to these management practices. Maize crops were grown at Balcarce, Argentina during four seasons. Treatments included two rates of N (i.e., 120 kg N ha−1 or non-fertilized during Seasons 1 and 2) or three plant densities (4, 8 and 12 plants m−2 with no N limitations, during Seasons 3 and 4). Measurements comprised (i) soil water content, evaporation and intercepted photosynthetically active radiation (iPAR) during the whole crop season, and (ii) shoot dry matter at physiological maturity (PM). Crop evapotranspiration (ET) was calculated by means of a water balance and soil evaporation (E) was estimated with micro-lysimeters. Crop transpiration (T) was estimated as the difference between ET and E; RUEB and WUE(B, T, s) were estimated from the ratio between crop biomass at PM and seasonal iPAR or T, respectively; and gc was estimated as T/iPAR (mm MJ−1). Higher N supply and plant densities positively affected WUE(B, ET, s) of maize crops, by increasing WUE(B, T, s) (ca. 19% for N supply and 8–12% for plant density) in addition to decreasing soil water evaporation. Changes in WUE(B, T, s) due to N supply were accounted by RUEB changes while gc was the main trait contributing to WUE(B, T, s) response to plant density. Crop conductance significantly decreased with maximum LAI increments up to 3.9. This work highlights the importance of considering crop conductance changes in response to management practices such as changing plant density.

Temperature and solar radiation during grain filling are the main drivers of grain weight and composition in several crops. While significant progress has been done on the effect of solar radiation intercepted by the plants (ISR) on grain weight (GW, mg) and oil content (OC, mg grain−1) of sunflower (Helianthus Annus L.), the effects of temperature on these traits are far from clear. As temperature affects the rate of plant development, increasing temperature would shorten grain filling duration and so, the critical period for ISR effect on GW and OC (indirect effect of temperature). However, direct effects of temperature non-mediated by ISR accumulation could also affect these traits. The objectives of this work were a) to characterize the responses of grain weight and oil content to mean temperature during grain filling in two traditional sunflower hybrids and b) to determine whether these responses can be exclusively explained by changes in ISR or any direct effect of temperature should also be considered. Two experimental approaches have been used to address these objectives: i) temperature manipulation at constant incident radiation in growth chambers; ii) modification of radiation interception in the field in different locations and years (different mean temperatures). Growth chamber experiments showed that GW and OC respond to temperature in a plateau lineal shape. At low incident radiation such as that of growth chambers, temperature effects on GW can be exclusively explained by reductions in ISR, while both direct and indirect effects of MT are evident on OC. Results obtained in field experiments confirmed this behavior at low radiation. Both GW and OC exponentially increased up to a maximum with ISR disregarding MT. Mathematical models were established to describe the responses of GW and OC to MT and ISR. These models consider MT x ISR interactive effects on GW; and MT - ISR additive effects on OC. The combination of growth chamber and field experiments observations allowed to unravel different mechanisms underlying the responses of GW and OC to temperature: at low incident radiation intensity, increasing temperature decreased GW exclusively by reducing ISR accumulation (indirect effects) while at higher radiation, temperature displays both direct (non-mediated by ISR) and indirect (ISR mediated) effects on GW. OC is affected by temperature in both direct and indirect way disregarding ISR. This work constitutes an important contribution towards understanding the effect of temperature during grain filling on sunflower yield and its relationship to solar radiation effects.

Corn stover is a biogas feedstock capable of enhancing agriculture bioenergy potential. Although the influence of growing conditions on biogas yield of corn stover has been reported, the joint effects of water and nitrogen on biogas production potential have not been addressed. A two year experiment (Exp. 1 and Exp. 2) was conducted in Balcarce, Argentina to assess nitrogen supply effects on stover composition and potential methane yield of corn crops grown under contrasting water regimes. Treatments were a combination of two nitrogen fertilization doses (0 and 120 kg ha−1) and two water regimes (irrigated and rainfed). Biomass composition (mass closure procedure) was determined, a BMP test was carried out and first-order kinetic parameters were obtained. Interactive effects of nitrogen and water on stover composition were found. BMP tests showed that the biogas production rate (k) decreased upon irrigation while its response to nitrogen depended on water availability. Nitrogen supply decreased specific biogas potential (Bmax) independently of water availability. Methane yield increased with nitrogen fertilization under irrigation, while it decreased under rainfed conditions. The observed water and nitrogen supply interactive effects on stover yield, methane yield and biomass conversion efficiency highlights the importance of considering the joint effects of multiple factors when trying to assess the effects of the environment on biomass quality for bioenergy purposes.

The weight and composition of soybean seeds (Glycine Max L. Merrill) depend on changes in carbon and nitrogen assimilate supply during grain filling. Soybean pods and seeds are green, evidencing their capacity to capture light. However, the current physiological knowledge does not consider any effect of incident solar radiation reaching the pods on seed weight and composition. The objective of this work was to investigate the response of seed weight and composition to changes in assimilate supply from leaves, to the incident solar radiation reaching the pods and to the combination of both, changes in assimilate supply from the leaves and incident solar radiation on pods of soybean plants. Field experiments were performed during two growing seasons at Balcarce, Argentina. Treatments modified the amount of assimilates supplied by the leaves (plant shading, defoliation), the solar radiation reaching the pods (pod shading) or both (defoliation and pod shading) during seed filling. Plant shading and defoliation reduced seed weight, oil concentration and oil and protein content and increased the concentration of saturated and poli-unsaturated fatty acids while reduced oleic acid percentage. Pod shading increased the concentration of stearic acid and reduced the concentration of linolenic acid. When pods were shaded on defoliated plants, seed weight and oil and protein content decreased while fatty acid composition was similar to values obtained under defoliation treatment. Based on these results, a conceptual model that considers photoheterotrophic nature of reproductive structures of soybean is proposed. Seed weight, oil and protein content and oil fatty acid composition depended on assimilate availability for the seeds. The response of oil and protein content to assimilate supply depended on whether leaves were present or not. The effect of solar radiation incident on pods depended on the amount of assimilates available for the seeds: (i) when carbon allocated was low (defoliation treatments), pods contributed to seed carbon economy but solar radiation incident on them did not affect fatty acid composition; (ii) when carbon allocated to the seeds was high (intact plants), contribution of pods to seed carbon economy was not significant, but the amount of solar radiation incident on pods produced significant changes in fatty acid composition. Fil: Bianculli, Mariana Lujan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina Fil: Aguirrezábal, Luis Adolfo Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina Fil: Pereyra Irujo, Gustavo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Echarte, Maria Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina

This study quantified maize (Zea mays L.) water use efficiency for grain yield (WUEg) in response to plant density under contrasting water regimes; and focused on relevant eco-physiologial processes underlying the responses of maize WUEg to plant density (i.e., the proportion of transpiration in the total water used, T/ET; and the crop growth rate during the critical period for kernel set, CGRcp). Maize crops were grown at Balcarce, Argentina during two seasons. Treatments included two water regimes (i.e., rainfed and irrigated) and three plant densities (4, 8 and 12 plants m−2). Measurements comprised (i) soil water content and iPAR during the whole growing season, (ii) shoot biomass around silking and (iii) grain yield and shoot biomass at physiological maturity. Crop ET was calculated by means of water balance and soil evaporation was measured with micro-lysimeters. The response of WUEg to increasing plant density from 4 to 8 or from 4 to 12 plants m−2 was influenced by seasonal water supply. Both seasonal ET and T/ET consistently increased with plant densities across contrasting water regimes. Although increments in T/ET partition were in accordance with increasing iPAR, they did not promote higher WUEg at low water supply. Grain yield increased with plant density, except in the driest environment where no response of either grain yield nor WUEg to plant density was detected. Our results showed that the response of CGRcp to plant density increments (i) depended on the water supply, and (ii) contributed to explain WUEg response to plant density under contrasting water supplies.

We evaluated the influence of the termination dates of a winter cover crop on (i) soil water availability during soybean (Glycine max L. (Merr)) growing season, (ii) soybean evapotranspiration (ET) and iii) water productivity in soybean (WP = Grain yield/ET) in a humid environment (i.e., 50 % of years with annual rainfall ≥900 mm). Experiments were carried out at Balcarce, Argentina during two growing seasons. Treatments included (i) soybean monoculture, (ii) soybean following a cover crop with an early termination date, and (iii) soybean following a cover crop with a delayed termination date (∼25 days later than the early one). Oat (Avena sativa L.) was used as a cover crop. Soil water content was measured with a neutron probe from cover crop sowing to soybean physiological maturity, and soybean ET was calculated by means of a soil water balance. Cover crop shoot biomass was determined immediately before termination dates and soybean grain yield was quantified at physiological maturity. Cover crops reduced soil available water (SAW) at cover crops termination date from 18 to 23 mm at early and delayed termination dates, respectively; and reductions were mostly evident in the upper 40 cm of the soil profile. Termination delays of around 25 days increased 60 % cover crops shoot biomass production, and promoted larger SAW reductions at termination date. However, cover crops had little impact on SAW during soybean growing season and they did not influence soybean grain yield. Moreover, our findings evidenced that in this humid environment (i) soybean ET was reduced between 12 and 17 mm following a cover crop, (ii) larger soybean ET reductions were associated with larger cover crops shoot biomass production, and (iii) WP in soybean was slightly improved (4–10%) by the inclusion of a cover crop.

The fatty acid composition of sunflower (Helianthus annuus L.) oil closely depends on the environmental conditions during grain filling. Temperature and solar radiation are the main environmental factors driving oil fatty acid composition. Minimum night temperature and intercepted solar radiation per plant (ISR) during grain filling independently affect oleic acid percentage of traditional sunflower oil. Critical period for temperature effect on this trait has been shown to be placed between 100 and 300ºC day after flowering (ºCd af). The period of maximal sensitivity of fatty acid composition to ISR remains unknown. The aim of the present work was to identify the time window of high sensitivity (critical period) of fatty acid composition to ISR of sunflower oil. For this, ISR was modified by shading (50 or 80%) or thinning (50%) field grown sunflower hybrid DK3820 during different periods of grain filling. The timing of maximal sensitivity of fatty acid composition to source variations at post flowering periods was explored and analyzed by two widely used approaches: i) evaluation of the relative oleic acid percentage under short shading treatments in relation to the control; ii) window-pane analysis of the response of oleic acid percentage to ISR. The first approach provided different critical periods depending on the level of radiation reduction. By the second approach, a developmental interval during which oleic acid was most sensitive to ISR regardless of the radiation level was determined. The critical period began at 350ºCd af and ended at 450ºCd af. Critical period of radiation effect on oleic acid concentration differed from radiation effect on grain weight and oil concentration and from the critical period of temperature effect on oil fatty acid composition. Different critical periods for different traits and specific environmental factors are indicative of the complexity of the interaction between environmental conditions and grain growth and oil synthesis dynamics. Fil: Echarte, Maria Mercedes. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires. Estación Experimental Agropecuaria Balcarce. Area de Investigación en Agronomía; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata; Argentina Fil: Puntel, Laila Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata; Argentina Fil: Aguirrezábal, Luis Adolfo Nazareno. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias. Departamento de Producción Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata; Argentina

As part of pioneering efforts to assess the potential of native microalgae as biofuel feedstock in South-Eastern Buenos Aires, 34 monoalgal cultures (corresponding to the Phylum Chlorophyta) were established and 21 were selected for further growth and biomass composition characterization. Novel RNA sequences in the ITS1-5.8S-ITS2 region were identified. Some strains showed desirable traits as biodiesel feedstock such as (i) apparent maximal doubling times of 6h, (ii) lipids accumulation of up to 43% of their dry biomass, (iii) high ration of mono-unsaturated to poly-unsaturated fatty acids, (iv) high response to CO(2) supplementation, and (v) complete sedimentation in 4h. Data of the outdoors performance of some strains suggested they might represent valuable resources for future research towards the regional development of the technology for microalgae-based biofuels.

Fatty acid composition of Helianthus annuus L. (sunflower) oil depends on intercepted solar radiation per plant (ISR) during grain filling. This effect could be accounted for by the assimilate availability of the grains (the source-sink ratio). However, the current physiological-biochemical knowledge does not consider any effect of carbon availability on oil fatty acid composition. The objective of this work was to address the regulation of fatty acid composition by assimilate supply to sunflower grains. A wide range of source-sink ratios was obtained by manipulating either the source or the sink during grain filling. Assimilate supply was also modified by injecting sucrose into the receptacle of sunflower capitula. Grain weight and oil content depended on both ISR and source-sink ratio in a curvilinear manner. When sink size was decreased by grain excision, ISR failed to explain oil fatty acid composition, while source-sink ratio appropriately described it. Sucrose injection significantly increased grain weight, oil content, and oleic acid percentage of shaded plants. It is concluded that effects of ISR on fatty acid composition are a consequence of changes in assimilate availability for grain oil synthesis. To explain these results a conceptual model is proposed: when assimilate supply limits grain growth and oil synthesis, mainly linoleic acid is synthesized. As the assimilate supply increases, oleic acid desaturation process gets saturated and oleic acid accumulates.

Oil fatty acid composition of sunflower ( Helianthus annuus L.) closely depends on the environmental conditions during grain filling. Temperature and solar radiation are main environmental factors driving oil chemical composition, as revealed by experiments in which the effects of these variables were investigated separately. The present work aims at investigating whether both temperature and irradiance act independently or they interact in exerting their effects on oleic acid percentage of sunflower oil. With this purpose, minimum night temperature (MNT) and intercepted solar radiation (ISR) per plant were together modified during the grain filling period of the traditional sunflower hybrid ACA 885. Two experimental approaches were performed: (a) radiation was modified in three locations at different latitudes (location × radiation experiments), (b) radiation and temperature were modified in a factorial design within one location by using field shelters ( in situ temperature × radiation experiments). Regardless location or year effect, oleic acid percentage increased with ISR per plant up to a maximum value, which depended on MNT. In situ temperature × radiation experiments showed that plant heating increased oleic acid percentage under any radiation condition assayed, while plant shading produced a drop in oleic acid that was independent of MNT. Statistically significant interaction between MNT and ISR per plant was not detected. A mathematical relationship that considered that MNT and ISR per plant additively contribute to oleic acid percentage was established and verified using data from location × radiation experiments. This equation predicted well independent experimental data from in situ temperature × radiation experiments. Results obtained in this work could improve model prediction of oil quality of sunflower grown under different environmental conditions, and contribute to unravel the mechanisms underlying oleic acid percentage in sunflower oil.

The observation that several cargoes move bidirectionally along microtubules in vivo raised the question regarding how molecular motors with opposed polarity coordinate during transport. In this work, we analyzed the switch of microtubule motors during the transport of melanosomes in Xenopus melanophores by registering trajectories of these organelles moving along microtubules using a fast and precise tracking method. We analyzed in detail the intervals of trajectories showing reversions in the original direction of transport and processive motion in the opposite direction for at least 250 nm. In most of the cases, the speed of the melanosome before the reversion slowly decreases with time approaching zero then, the organelle returns over the same path moving initially at a very high speed and slowing down with time. These results could be explained according to a model in which reversions are triggered by an elastic collision of the cargo with obstacles in the cytosol. This interaction generates a force opposed to the movement of the motor-driven organelle increasing the probability of detaching the active motors from the track. The model can explain reversions in melanosome trajectories as well as other characteristics of in vivo transport along microtubules observed by other authors. Our results suggest that the crowded cytoplasm plays a key role in regulating the coordination of microtubules-dependent motors. © 2008 Humana Press Inc. Fil: Bruno, Luciana. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Echarte, Maria Mercedes. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; Argentina Fil: Levi, Valeria. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

The plasma membrane calcium ATPase (PMCA) reacts with ATP to form acid-stable phosphorylated intermediates (EP) that can be measured using (gamma-32P)ATP. However, the steady-state level of EP at [ATP] higher than 100 microM has not yet been studied due to methodological problems. Using a microscale method and a purified preparation of PMCA from human red blood cells, we measured the steady-state concentration of EP as a function of [ATP] up to 2 mM at different concentrations of Mg2+, both at 4 and 25 degrees C. We have measured the Ca2+-ATPase activity (v) under the same conditions as those used for phosphorylation experiments. While the curves of ATPase activity vs [ATP] were well described by the Michaelis-Menten equation, the corresponding curves of EP required more complex fitting equations, exhibiting at least a high- and a low-affinity component. Mg2+ increases the apparent affinity for ATP of this latter component, but it shows no significant effect on its high-affinity one or on the Ca2+-ATPase activity. We calculated the turnover of EP (k(pEP)) as the ratio v/EP. At 1 mM Mg2+, k(pEP) increases hyperbolically with [ATP], while at 8 microM Mg2+, it exhibits a behavior that cannot be explained by the currently accepted mechanism for ATP hydrolysis. These results, together with measurements of the rate of dephosphorylation at 4 degrees C, suggest that ATP is acting in additional steps involving the interconversion of phosphorylated intermediates during the hydrolysis of the nucleotide.

Grain quality is a complex character primarily determined by processes at the crop level. This chapter reviews the effects of environment, genotype, and their interactions, on grain oil and protein concentration and composition. The focus is on sunflower as an oilseed model and bread wheat as a cereal model. Sunflower oil composition is analyzed in terms of concentration and composition of fatty acids, tocopherols and phytosterols while, in bread wheat, grain prolamin composition is considered. Process-based crop models accounting for grain yield in both species, and for concentration and composition of oil (sunflower) and protein (wheat) are described. A combination of modeling and experiments allowed analysis of the relationships between quality traits and yield. Finally, we use physiologically-based relationships of yield and oil attributes (sunflower) and yield and protein attributes (wheat) to design management and breeding strategies for grain quality improvement.

P-ATPases are characterized by the formation of acid-stable phosphorylated intermediates (EP) during their reaction cycle. We have developed a microscale method to determine EP that involves the phosphorylation of the enzyme using [gamma-(32)P]ATP and precipitation with TCA; separation of the sample by SDS-PAGE, and measurement of the enzyme protein and (32)P-labeled EP by digital analysis of both the stained gel and its autoradiogram, respectively. The principal advantages of this method over typical procedures (filtration and centrifugation) are the low amount of enzyme required and the substantial decrease in the blank values and data scattering produced by unspecific phosphorylation and nonquantitative recovering of the enzyme. Application of this new method to a purified preparation of the plasma membrane calcium ATPase (PMCA) results in overcoming the difficulties of measuring EP at high ATP concentrations. A biphasic behavior of the substrate curve for EP was observed when the study was extended to ATP levels within the physiological range. Since, in principle, the method does not require the use of highly purified preparations, it could be helpful for the study of phosphorylated intermediates especially under conditions in which small amounts of protein are available, e.g., mutated variants of P-ATPases.

Thermal stability of plasma membrane Ca2+ pump was systematically studied in three micellar systems of different composition, and related with the interactions amphiphile-protein measured by fluorescence resonance energy transfer. Thermal denaturation was characterized as an irreversible process that is well described by a first order kinetic with an activation energy of 222 ± 12 kJ/mol in the range 33-45°C. Upon increasing the mole fraction of phospholipid in the mixed micelles where the Ca2+ pump was reconstituted, the kinetic coefficient for the inactivation process diminished until it reached a constant value, different for each phospholipid species. We propose a model in which thermal stability of the pump depends on the composition of the amphiphile monolayer directly in contact with the transmembrane protein surface. Application of this model shows that the maximal pump stability is attained when 80% of this surface is covered by phospholipids. This analysis provides an indirect measure of the relative affinity phospholipid/detergent for the hydrophobic transmembrane surface of the protein (K(LD)) showing that those phospholipids with higher affinity provide greater stability to the Ca2+ pump. We developed a method for directly measure K(LD) by using fluorescence resonance energy transfer from the membrane protein tryptophan residues to a pyrene-labeled phospholipid. K(LD) values obtained by this procedure agree with those obtained from the model, providing a strong evidence to support its validity. Fil: Levi, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Rossi, Juan Pablo Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Echarte, Maria Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Castello, Pablo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina Fil: Gonzalez Flecha, Francisco Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

The retrograde transport of nerve growth factor (NGF) in neurite-like processes of living differentiated PC12 cells was studied using streptavidin-quantum dots (QDs) coupled to monobiotin-NGF. These reagents were active in differentiation, binding, internalization, and transport. Ten-35% of the QD-NGF-receptor complexes were mobile. Quantitative single particle tracking revealed a bidirectional step-like motion, requiring intact microtubules, with a net retrograde velocity of 0.054+/-0.020 microm/s. Individual runs had a mean velocity of approximately 0.15 microm/s at room temperature, and the run times were exponentially distributed. The photostability and brightness of QDs permit extended real-time analysis of individual QDbNGF- receptor complexes trafficking within neurites.