Differences in Al tolerance between Plantago algarbiensis and P. almogravensis reflect their ability to respond to oxidative stress

We evaluated the impact of low pH and aluminum (Al) on the leaves and roots of Plantago almogravensis Franco and Plantago algarbiensis Samp., focusing on energy partitioning in photosystem II, H₂O₂ levels, lipid peroxidation, electrolyte leakage (EL), protein oxidation, total soluble protein content and antioxidant enzyme activities. In both species, Al triggered more changes in oxidative metabolism than low pH alone, particularly in the roots. We found that Al increased the levels of H₂O₂ in P. algarbiensis roots, but reduced the levels of H₂O₂ in P. almogravensis leaves and roots. Neither low pH nor Al affected the spatial heterogeneity of chlorophyll fluorescence, the maximum photochemical efficiency of PSII (F_v/F_m), the actual quantum efficiency of PSII (?_PSII) or the quantum yields of regulated (?_NPQ) and nonregulated (?_NO) energy dissipation, and there was no significant change in total soluble protein content and EL. In P. algarbiensis, Al increased the carbonyl content and the activities of superoxide dismutase (SOD) and catalase (CAT) in the roots, and also CAT, ascorbate peroxidase and guaiacol peroxidase activities in the leaves. In P. almogravensis, Al reduced the level of malondialdehyde in the roots as well as SOD activity in the leaves and roots. We found that P. almogravensis plantlets could manage the oxidative stress caused by low pH and Al, whereas the P. algarbiensis antioxidant system was unable to suppress Al toxicity completely, leading to the accumulation of H₂O₂ and consequential protein oxidation in the roots.     

Forest cover, extinction thresholds and time lags in woody plants (Myrtaceae) in the Brazilian Atlantic Forest: resources for conservation

Efforts to conserve tropical forests could be strengthened based on ecological knowledge, such as extinction thresholds in ecological processes. Many studies of extinction thresholds associated with habitat reduction have focused on animals, generally at the patch scale. However, certain plant groups are very interesting models with which to study this type of relationship, such as Myrtaceae in Neotropical forests. Because trees are long-lived organisms, local extinctions in response to habitat loss may occur in different ways due to a time lag. In this study, our objective was to assess the occurrence of extinction thresholds at the landscape scale for Myrtaceae in a large biome and the pattern of species reduction in different tree size classes. We studied nine landscapes with different amounts of available habitat (between 5 and 55 % forest cover) in different parts of the Atlantic Forest in Bahia, Brazil, and in each landscape, we evaluated four plant classes based on tree circumference: saplings (CBH between 8 and 15 cm), young (CBH between 15 and 30 cm) adults (CBH ≥30 cm) and total (all individuals with CBH ≥8 cm). Landscapes with forest cover less than 25 % presented an approximately sixfold reduction in Myrtaceae total species richness compared with landscapes with forest cover greater than 40 %. We identified a relationship with a threshold between the amount of available habitat at the landscape level and Myrtaceae richness, with a reduction in total, sapling and young species below a threshold of 40 % forest cover, whereas adults had an extinction threshold at 30 % forest cover. We discuss the differences among the categories of plants associated with a time lag and the possibilities and limitations in applying these results in environmental management.     

Landscape context determinants to plant diversity in the permanent meadows of Southern European Alps

In the Southern Alps, the role of landscape context on meadows plant diversity was evaluated using a multi-model information theoretic approach and five competing hypotheses of landscape context factors: habitat quality (H1), matrix quality (H2), habitat change (H3), matrix quality change (H4) and topography-environmental conditions (H5)- measured at three spatial scales (125, 250 and 500 m). Shannon diversity index and species richness represented plant diversity obtained in 34 plots (100 m² size). Landscape context affected plant diversity measures differently. Matrix quality change at larger scale (500 m) was the most supported hypothesis explaining Shannon diversity index, while species richness responded mostly to topography-environmental conditions in the immediate surroundings (125 m). No effects of present-day habitat and matrix quality (H1 and H2) were found. Matrix quality change affected positively Shannon diversity index through an effect of landscape neighbourhood context on farming management practices. Due to the importance of exposure and inclination of slopes, topography-environmental conditions influenced species richness mostly through energy-driven processes and farming management strategies. In terms of scale, matrix quality change was the strongest hypothesis explaining Shannon diversity index at all scales, while the underlying process affecting species richness changed with scale (H5 or H3). Overall, landscape context explained only 25–28 % of the variation in plant diversity, suggesting that landscape management may support biodiversity conservation when comprised in a global strategy including farming practices. In the study area, change in landscape diversity may be a good indicator for Shannon diversity index and south-eastern facing meadows should be preserved.     

Heat Treatment and β-Carotene Incorporation Effect in the Interaction of β-Lactoglobulin and Carboxymethylcellulose System

Encapsulation technologies using proteins or polysaccharides can be employed with the purpose of solubilizing and protecting carotenoids. However, information on the role of protein and polysaccharide interactions is still slightly limited. The aim of this work was to investigate the effect of β-carotene linked to protein β-lactoglobulin (BLG) in the interaction carboxymethylcellulose (CMC) using isothermal titration calorimetry (ITC). Firstly, BLG and CMC interaction was assessed by means of turbidity analysis. Based on the results of turbidity, the thermodynamic profile of BLG-CMC complexes at pH 4.0 was obtained using ITC analysis at 25 °C. Afterward, it was evaluated the effect of a thermal treatment applied to the BLG (68 °C for 50 min) in the interaction with CMC also using ITC and circular dichroism (CD). ITC and CD analysis showed that the heat treatment applied on BLG did not cause changes in molecular interactions. The binding isotherm of BLG-CMC complexes incorporated with β-carotene showed an increase in the molar ratio and a slight decrease in enthalpy of the system. Incorporation of β-carotene in the system did not significantly affect the BLG and CMC interaction, suggesting this system can be applied in food application as encapsulation.     

QTL mapping for resistance to Ceratocystis wilt in <Emphasis Type="Italic">Eucalyptus</Emphasis>

Ceratocystis wilt caused by the fungus Ceratocystis fimbriata, is currently one of the major diseases in commercial plantations of Eucalyptus trees in Brazil. Deployment of resistant genotypes has been the main strategy for effective disease management. The present study aimed at identifying genomic regions underlying the genetic control of resistance to Ceratocystis wilt in Eucalyptus by quantitative trait loci (QTL) mapping in an outbred hybrid progeny derived from a cross between (Eucalyptus dunnii × Eucalyptus grandis) × (Eucalyptus urophylla × Eucalyptus globulus). A segregating population of 127 individuals was phenotyped for resistance to Ceratocystis wilt using controlled inoculation under a completely randomized design with five clonal replicates per individual plant. The phenotypic resistance response followed a continuous variation, enabling us to analyze the trait in a quantitative manner. The population was genotyped with 114 microsatellite markers and 110 were mapped with an average interval of 12.3 cM. Using a sib-pair interval-mapping approach five QTLs were identified for disease resistance, located on linkage groups 1, 3, 5, 8, and 10, and their estimated individual heritability ranged from 0.096 to 0.342. The QTL on linkage group 3 overlaps with other fungal disease-resistance QTLs mapped earlier and is consistent with the annotation of several disease-resistance genes on this chromosome in the E. grandis genome. This is the first study to identify and attempt to quantify the effects of QTLs associated with resistance to Ceratocystis wilt in Eucalyptus.     

Power consumption evaluation of different fed-batch strategies for enzymatic hydrolysis of sugarcane bagasse

The minimization of costs in the distillation step of lignocellulosic ethanol production requires the use of a high solids loading during the enzymatic hydrolysis to obtain a more concentrated glucose liquor. However, this increase in biomass can lead to problems including increased mass and heat transfer resistance, decreased cellulose conversion, and increased apparent viscosity with the associated increase in power consumption. The use of fed-batch operation offers a promising way to circumvent these problems. In this study, one batch and four fed-batch strategies for solids and/or enzyme feeding during the enzymatic hydrolysis of sugarcane bagasse were evaluated. Determinations of glucose concentration, power consumption, and apparent viscosity were made throughout the experiments, and the different strategies were compared in terms of energy efficiency (mass of glucose produced according to the energy consumed). The best energy efficiency was obtained for the strategy in which substrate and enzyme were added simultaneously (0.35 kg_glucose kWh^?1). This value was 52 % higher than obtained in batch operation.     

Investigating the effects of point mutations on the affinity between the cyanobacterial lectin microvirin and high mannose-type glycans present on the HIV envelope glycoprotein

Human immunodeficiency virus (HIV) infections continue to exert an enormous impact on global human health. This led experts to emphasize the importance of new measures for preventing HIV infections, including the development of vaccines and novel drugs. In this context, a promising approach involves the use of lectins that can bind the surface envelope glycoprotein gp120 of HIV with high affinity, preventing viral entry. The cyanobacterial lectin microvirin (MVN) has been proposed as a candidate for development as a topical microbicide because of its ability to bind to high mannose-type glycans, potently inhibiting HIV-1 entry. Thus, the aim of this computational study was to investigate the effects of four point mutations (D53Q, D53E, D53K, and D53W) on the structure and affinity of MVN with di-mannose (MAN). Molecular dynamics simulations followed by binding free energy calculations using MM-GBSA were employed. The calculated binding free energy of ligand-receptor complexation of MVN with MAN was ?26.02 kcal mol^-1. We identified in the wild-type protein that residues I45, T59, and Q81 have a major contribution to the binding free energy of di-mannose. Among the investigated mutants, the most promising one was the D53W mutation, with a theoretical binding free energy value of ?29.16 kcal mol^-1. We suggest that this increased stability is due to the introduction of extra rigidity on the hinge region connecting two key structural elements of the MVN binding site.