Mitochondrial and peroxisomal NAD+ uptake are important for improved photosynthesis and seed yield under elevated CO2 concentrations.

As sessile organisms, plants must adapt their physiology and developmental processes to cope with challenging environmental circumstances, such as the ongoing elevation in atmospheric carbon dioxide (CO2 ) levels. Nicotinamide adenine dinucleotide (NAD+ ) is a cornerstone of plant metabolism and plays an essential role in redox homeostasis. Given that plants impaired in NAD metabolism and transport often display growth defects, low seed production and disturbed stomatal development/movement, we hypothesized that subcellular NAD distribution could be a candidate for plants to exploit the effects of CO2 fertilization. We report that an efficient subcellular NAD+ distribution is required for the fecundity-promoting effects of elevated CO2 levels. Plants with reduced expression of either mitochondrial (NDT1 or NDT2) or peroxisomal (PXN) NAD+ transporter genes grown under elevated CO2 exhibited reduced total leaf area compared with the wild-type while PXN mutants also displayed reduced leaf number. NDT2 and PXN lines grown under elevated CO2 conditions displayed reduced rosette dry weight and lower photosynthetic rates coupled with reduced stomatal conductance. Interestingly, high CO2 doubled seed production and seed weight in the wild-type, whereas the mutants were less responsive to increases in CO2 levels during reproduction, producing far fewer seeds than the wild-type under both CO2 conditions. These data highlight the importance of mitochondrial and peroxisomal NAD+ uptake mediated by distinct NAD transporter proteins to modulate photosynthesis and seed production under high CO2 levels.

Assessing nystatin cream treatment efficacy against Leishmania (L.) amazonensis infection in BALB/c model.

The current scenario for cutaneous leishmaniasis treatment includes the use of first and second-choice drugs, both therapeutic strategies presenting several adverse effects and being related to an increment of treatment-refractory parasite strains. These facts encourage the search for new treatment approaches, including repositioning drugs, such as nystatin. Although in vitro assays show that this polyene macrolide compound has leishmanicidal activity, no in vivo evidence for a similar activity has been shown so far for the commercial nystatin cream formulation. This work assessed the effects of nystatin cream (25,000 IU/g) administered on mice in an amount to completely cover the paw surface of BALB/c mice infected with Leishmania (L.) amazonensis once a day, until a total of up to 20 doses. The data presented herein points to unequivocal evidence that treatment with this formulation causes a statistically significant reduction of swelling/edema in mice paws when compared to animal groups not submitted to this treatment regimen after the fourth week of infection: lesion sizes at the sixth (p = 0.0159), seventh (p = 0.0079) and eighth (p = 0.0079) week. Furthermore, swelling/edema reduction relates to a decrease in parasite load in the footpad (∼48%) and in draining lymph nodes (∼68%) at eight weeks post-infection. This is the first report of the effectiveness of nystatin cream used as a topical treatment in BALB/c model for cutaneous leishmaniasis.

A New Strategy for Mapping Epitopes of LACK and PEPCK Proteins of Leishmania amazonensis Specific for Major Histocompatibility Complex Class I.

Leishmaniasis represents a complex of diseases with a broad clinical spectrum and epidemiological diversity, considered a major public health problem. Although there is treatment, there are still no vaccines for cutaneous leishmaniasis. Because Leishmania spp. is an intracellular protozoan with several escape mechanisms, a vaccine must provoke cellular and humoral immune responses. Previously, we identified the Leishmania homolog of receptors for activated C kinase (LACK) and phosphoenolpyruvate carboxykinase (PEPCK) proteins as strong immunogens and candidates for the development of a vaccine strategy. The present work focuses on the in silico prediction and characterization of antigenic epitopes that might interact with mice or human major histocompatibility complex class I. After immunogenicity prediction on the Immune Epitope Database (IEDB) and the Database of MHC Ligands and Peptide Motifs (SYFPEITHI), 26 peptides were selected for interaction assays with infected mouse lymphocytes by flow cytometry and ELISpot. This strategy identified nine antigenic peptides (pL1-H2, pPL3-H2, pL10-HLA, pP13-H2, pP14-H2, pP15-H2, pP16-H2, pP17-H2, pP18-H2, pP26-HLA), which are strong candidates for developing a peptide vaccine against leishmaniasis.

Detection of Antibodies against Hepatitis A Virus (HAV) by a Surface Plasmon Resonance (SPR) Biosensor: A New Diagnosis Tool Based on the Major HAV Capsid Protein VP1 (SPR-HAVP1).

Hepatitis A (HA) is an acute human infectious disease caused by a positive single-stranded RNA virus (HAV). It is mainly acquired through the fecal-oral route and is primarily spread by contact between people and exposure to contaminated water and food. Recently, large outbreaks of HA have been reported by low and moderate endemicity countries, emphasizing its importance in public health and the need for rapid and large-scale diagnostic tests to support public health decisions on HA. This work proposes a new tool for HAV diagnosis based on the association of surface plasmonic resonance with major capsid protein VP1 (SPR-HAVP1 assay), detecting IgM antibodies for HAV in human serum samples. Structural analyses of VP1 B-lymphocyte epitopes showed continuous and discontinuous epitopes. The discontinuous epitopes were identified in the N-terminal region of the VP1 protein. Both epitope types in the VP1 protein were shown by the reactivity of VP1 in native and denaturing conditions to IgM anti-HAV, which was favorable to tests of VP1 in the SPR assays. SPR-HAVP1 assays showed good performance in the detection of IgM polyclonal antibody anti-HAV. These assays were performed using a COOH5 sensor chip functionalized with VP1 protein. The sensorgram record showed a significant difference between positive and negative serum samples, which was confirmed by analysis of variation of initial and final dissociation values through time (ΔRUd/t). The data gathered here are unequivocal evidence that the SPR-HAVP1 strategy can be applied to detect IgM antibodies in human serum positive to the HAV. This is a new tool to be explored to diagnose human HAV infections.

SARS-CoV-2 Proteins Bind to Hemoglobin and Its Metabolites.

(1) Background: coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been linked to hematological dysfunctions, but there are little experimental data that explain this. Spike (S) and Nucleoprotein (N) proteins have been putatively associated with these dysfunctions. In this work, we analyzed the recruitment of hemoglobin (Hb) and other metabolites (hemin and protoporphyrin IX-PpIX) by SARS-Cov2 proteins using different approaches. (2) Methods: shotgun proteomics (LC-MS/MS) after affinity column adsorption identified hemin-binding SARS-CoV-2 proteins. The parallel synthesis of the peptides technique was used to study the interaction of the receptor bind domain (RBD) and N-terminal domain (NTD) of the S protein with Hb and in silico analysis to identify the binding motifs of the N protein. The plaque assay was used to investigate the inhibitory effect of Hb and the metabolites hemin and PpIX on virus adsorption and replication in Vero cells. (3) Results: the proteomic analysis by LC-MS/MS identified the S, N, M, Nsp3, and Nsp7 as putative hemin-binding proteins. Six short sequences in the RBD and 11 in the NTD of the spike were identified by microarray of peptides to interact with Hb and tree motifs in the N protein by in silico analysis to bind with heme. An inhibitory effect in vitro of Hb, hemin, and PpIX at different levels was observed. Strikingly, free Hb at 1mM suppressed viral replication (99%), and its interaction with SARS-CoV-2 was localized into the RBD region of the spike protein. (4) Conclusions: in this study, we identified that (at least) five proteins (S, N, M, Nsp3, and Nsp7) of SARS-CoV-2 recruit Hb/metabolites. The motifs of the RDB of SARS-CoV-2 spike, which binds Hb, and the sites of the heme bind-N protein were disclosed. In addition, these compounds and PpIX block the virus's adsorption and replication. Furthermore, we also identified heme-binding motifs and interaction with hemin in N protein and other structural (S and M) and non-structural (Nsp3 and Nsp7) proteins.

In Silico Insights into the Mechanism of Action of Epoxy-α-Lapachone and Epoxymethyl-Lawsone in Leishmania spp.

Epoxy-α-lapachone (Lap) and Epoxymethyl-lawsone (Law) are oxiranes derived from Lapachol and have been shown to be promising drugs for Leishmaniases treatment. Although, it is known the action spectrum of both compounds affect the Leishmania spp. multiplication, there are gaps in the molecular binding details of target enzymes related to the parasite's physiology. Molecular docking assays simulations were performed using DockThor server to predict the preferred orientation of both compounds to form stable complexes with key enzymes of metabolic pathway, electron transport chain, and lipids metabolism of Leishmania spp. This study showed the hit rates of both compounds interacting with lanosterol C-14 demethylase (-8.4 kcal/mol to -7.4 kcal/mol), cytochrome c (-10.2 kcal/mol to -8.8 kcal/mol), and glyceraldehyde-3-phosphate dehydrogenase (-8.5 kcal/mol to -7.5 kcal/mol) according to Leishmania spp. and assessed compounds. The set of molecular evidence reinforces the potential of both compounds as multi-target drugs for interrupt the network interactions between parasite enzymes, which can lead to a better efficacy of drugs for the treatment of leishmaniases.

Atazanavir, Alone or in Combination with Ritonavir, Inhibits SARS-CoV-2 Replication and Proinflammatory Cytokine Production.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is already responsible for far more deaths than previous pathogenic coronaviruses (CoVs) from 2002 and 2012. The identification of clinically approved drugs to be repurposed to combat 2019 CoV disease (COVID-19) would allow the rapid implementation of potentially life-saving procedures. The major protease (Mpro) of SARS-CoV-2 is considered a promising target, based on previous results from related CoVs with lopinavir (LPV), an HIV protease inhibitor. However, limited evidence exists for other clinically approved antiretroviral protease inhibitors. Extensive use of atazanavir (ATV) as antiretroviral and previous evidence suggesting its bioavailability within the respiratory tract prompted us to study this molecule against SARS-CoV-2. Our results show that ATV docks in the active site of SARS-CoV-2 Mpro with greater strength than LPV, blocking Mpro activity. We confirmed that ATV inhibits SARS-CoV-2 replication, alone or in combination with ritonavir (RTV) in Vero cells and a human pulmonary epithelial cell line. ATV/RTV also impaired virus-induced enhancement of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) levels. Together, our data strongly suggest that ATV and ATV/RTV should be considered among the candidate repurposed drugs undergoing clinical trials in the fight against COVID-19.

An overview of the sandfly fauna (Diptera: Psychodidae) followed by the detection of Leishmania DNA and blood meal identification in the state of Acre, Amazonian Brazil.

BACKGROUND: In Acre state, Brazil, the dissemination of cutaneous leishmaniasis has increased in recent years, with limited knowledge of the potential Leishmania spp. vectors involved. OBJECTIVES: Here, data concerning the sandfly fauna of Brasiléia municipality, Leishmania DNA-detection rates and the identification of blood meal sources of insects captured in 2013-2015 are presented. METHODS: Parasite detection in female sandflies was performed individually by multiplex polymerase chain reaction (PCR) (Leishmania kDNA/sandfly cacophony-gene), with the identification of Leishmania spp. by hsp70-PCR and sequencing. The identification of blood gut-content from fed females was performed by cyt b-PCR and sequencing. FINDINGS: A total of 4,473 sandflies were captured. A subgroup of 864 non-blood-fed females evaluated for the presence of Leishmania DNA showed 2.9% positivity for Leishmania (Viannia) braziliensis and L. (V.) guyanensis. The identification of blood meal sources was performed in 96 blood-fed females, allowing the identification of 13 vertebrate species. In nine/96 fed females, DNA from L. (V.) shawi, L. (V.) guyanensis, L. (V.) braziliensis and Endotrypanum sp. was detected. MAIN CONCLUSIONS: In Brumptomyia sp. and Evandromyia termitophila, the first report of Leishmania DNA-detection is provided in Acre; Nyssomyia shawi is implicated as potential vector of L. (V.) braziliensis and L. (V.) guyanensis for the first time in Brazil.

Insights into the proteomic profile and gene expression of Lutzomyia longipalpis-derived Lulo cell line.

BACKGROUND: Lutzomyia longipalpis-derived cell line (Lulo) has been suggested as a model for studies of interaction between sandflies and Leishmania. OBJECTIVES: Here, we present data of proteomic and gene expression analyses of Lulo cell related to interactions with Leishmania (Viannia) braziliensis. METHODS: Lulo cell protein extracts were analysed through a combination of two-dimensional gel electrophoresis and mass spectrometry and resulting spots were further investigated in silico to identify proteins using Mascot search and, afterwards, resulting sequences were applied for analysis with VectorBase. RESULTS: Sixty-four spots were identified showing similarities to other proteins registered in the databases and could be classified according to their biological function, such as ion-binding proteins (23%), proteases (14%), cytoskeletal proteins (11%) and interactive membrane proteins (9.5%). Effects of interaction with L. (V.) braziliensis with the expression of three genes (enolase, tubulin and vacuolar transport protein) were observed after an eight-hour timeframe and compared to culture without parasites, and demonstrated the impact of parasite interaction with the expression of the following genes: LLOJ000219 (1.69-fold), LLOJ000326 (1.43-fold) and LLOJ006663 (2.41-fold). CONCLUSIONS: This set of results adds relevant information regarding the usefulness of the Lulo cell line for studies with Leishmania parasites that indicate variations of protein expression.

Zinc toxicity in seedlings of three trees from the Fabaceae associated with arbuscular mycorrhizal fungi.

Due to diverse human activities zinc (Zn) may reach phytotoxic levels in the soil. Here, we evaluated the differential sensibility of three Brazilian tree species from the Fabaceae to increasing soil Zn concentrations and its physiological response to cope with excess Zn. A greenhouse experiment was conducted with the species: Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, and the addition of 0, 200, 400 and 600 mg Zn kg-1 to the soil. Plants were harvested after three months of cultivation, and growth, root symbiosis, biochemical markers and elemental composition were analyzed. Soil Zn addition reduced seedling growth, irrespective of the species, with a strong reduction in M. caesalpiniaefolia. Regarding root symbiosis, in N2-fixing species, nitrogenase activity was reduced by the highest Zn concentrations. Zn addition caused plants nutritional imbalances, mainly in roots. The content of photosynthetic pigments in leaves decreased up to 40%, suggesting that high Zn contents interfered with its biosynthesis, and altered the content of foliar polyamines and free amino acids, depending on the species and the soil Zn concentration. Zn toxicity in M. caesalpiniaefolia plants was observed at available soil Zn concentrations greater than 100 mg kg-1 (DTPA-extractable), being the most sensitive species and E. speciosa was moderately sensitive. S. parahyba was a moderately tolerant species, which seems to be related to polyamines accumulation and to mycorrhizal association. This last species has the potential for revegetation of areas with moderately high soil Zn concentration and for phytostabilization purposes. Future research evaluating the tolerance to multiple metal stress under field conditions should confirm S. parayba suitability in Zn contaminated areas of tropical regions.

The Mitochondrial Thioredoxin System Contributes to the Metabolic Responses Under Drought Episodes in Arabidopsis.

Thioredoxins (Trxs) modulate metabolic responses during stress conditions; however, the mechanisms governing the responses of plants subjected to multiple drought events and the role of Trxs under these conditions are not well understood. Here we explored the significance of the mitochondrial Trx system in Arabidopsis following exposure to single and repeated drought events. We analyzed the previously characterized NADPH-dependent Trx reductase A and B double mutant (ntra ntrb) and two independent mitochondrial thioredoxin o1 (trxo1) mutant lines. Following similar reductions in relative water content (∼50%), Trx mutants subjected to two drought cycles displayed a significantly higher maximum quantum efficiency (Fv/Fm) and were less sensitive to drought than their wild-type counterparts and than all genotypes subjected to a single drought event. Trx mutant plants displayed a faster recovery after two cycles of drought, as observed by the higher accumulation of secondary metabolites and higher stomatal conductance. Our results indicate that plants exposed to multiple drought cycles are able to modulate their subsequent metabolic and physiological response, suggesting the occurrence of an exquisite acclimation in stressed Arabidopsis plants. Moreover, this differential acclimation involves the participation of a set of metabolic changes as well as redox poise alteration following stress recovery.

Identification and characterization of metabolite quantitative trait loci in tomato leaves and comparison with those reported for fruits and seeds.

INTRODUCTION: To date, most studies of natural variation and metabolite quantitative trait loci (mQTL) in tomato have focused on fruit metabolism, leaving aside the identification of genomic regions involved in the regulation of leaf metabolism. OBJECTIVE: This study was conducted to identify leaf mQTL in tomato and to assess the association of leaf metabolites and physiological traits with the metabolite levels from other tissues. METHODS: The analysis of components of leaf metabolism was performed by phenotypying 76 tomato ILs with chromosome segments of the wild species Solanum pennellii in the genetic background of a cultivated tomato (S. lycopersicum) variety M82. The plants were cultivated in two different environments in independent years and samples were harvested from mature leaves of non-flowering plants at the middle of the light period. The non-targeted metabolite profiling was obtained by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). With the data set obtained in this study and already published metabolomics data from seed and fruit, we performed QTL mapping, heritability and correlation analyses. RESULTS: Changes in metabolite contents were evident in the ILs that are potentially important with respect to stress responses and plant physiology. By analyzing the obtained data, we identified 42 positive and 76 negative mQTL involved in carbon and nitrogen metabolism. CONCLUSIONS: Overall, these findings allowed the identification of S. lycopersicum genome regions involved in the regulation of leaf primary carbon and nitrogen metabolism, as well as the association of leaf metabolites with metabolites from seeds and fruits.

Insights into the tracking of the cysteine proteinase B COOH-terminal polypeptide of Leishmania (Leishmania) amazonensis by surface plasmon resonance.

Leishmania (Leishmania) amazonensis has adaptive mechanisms to the host environment that are guided by its proteinases, including cysteine proteinase B (CPB), and primarily its COOH-terminal region (Cyspep). This work aimed to track the fate of Cyspep by surface plasmon resonance (SPR) of promastigotes and amastigotes to gain a greater understanding of the adaptation of this parasite in both hosts. This strategy consisted of antibody immobilization on a COOH1 surface, followed by interaction with parasite proteins and epoxysuccinyl-L-leucylamido(4-guanidino)butane (E-64). Pro-CPB and Cyspep were detected using specific polyclonal antibodies against a recombinant Cyspep in both parasite forms. The parasitic supernatants from amastigotes and promastigotes exhibited higher anti-Cyspep recognition compared with that in the subcellular fractions. As the supernatant of the promastigote cultures exhibited resonance unit values indicative of an effective with to E-64, this result was assumed to be Pro-CPB detection. Finally, after using three sequential SPR assay steps, we propose that amastigotes and promastigotes release Cyspep into the extracellular environment, but only promastigotes release this polypeptide as Pro-CPB.

Serine Proteinases in Leishmania (Viannia) braziliensis Promastigotes Have Distinct Subcellular Distributions and Expression.

Serine proteinases in Leishmania (Viannia) braziliensis promastigotes were assessed in this work. This study included the investigation of the enzymatic activity of subcellular fractions obtained from benzamidine affinity chromatography, reverse transcription polymerase chain reactions, and in silico assays of subcellular localization of subtilisin. Promastigote serine proteinases showed gelatinolytic activity with molecular masses of 43 kDa to 170 kDa in the cytosolic fraction and 67 kDa to 170 kDa in the membranous fraction. Serine proteinase activities were detected using N-benzyloxycarbonyl-l-phenylalanyl-l-arginine 7-amino-4-methylcoumarin (Z-FR-AMC) and N-succinyl-l-alanine-l-phenylalanine-l-lysine 7-amino-4-methylcoumarin (Suc-AFK-AMC) as substrates in the cytosolic fraction (Z-FR-AMC = 392 ± 30 µmol.min-1 mg of protein-1 and Suc-AFK-AMC = 252 ± 20 µmol.min-1 mg of protein-1) and in the membranous fraction (Z-FR-AMC = 53 ± 5 µmol.min-1 mg of protein-1 and Suc-AFK-AMC = 63.6 ± 6.5 µmol.min-1 mg of protein-1). Enzyme specificity was shown by inhibition with aprotinin (19% to 80% inhibition) and phenylmethanesulfonyl fluoride (3% to 69%), depending on the subcellular fraction and substrate. The expression of subtilisin (LbrM.13.0860 and LbrM.28.2570) and tryparedoxin peroxidase (LbrM.15.1080) genes was observed by the detection of RNA transcripts 200 bp, 162 bp, and 166 bp long, respectively. Subsequent in silico assays showed LbrM.13.0860 can be located in the cytosol and LbrM.28.2570 in the membrane of the parasite. Data obtained here show the subcellular distribution and expression of serine proteinases, including the subtilisin-like serine proteinases in L. (V.) braziliensis promastigotes.

The genetic architecture of photosynthesis and plant growth-related traits in tomato.

To identify genomic regions involved in the regulation of fundamental physiological processes such as photosynthesis and respiration, a population of Solanum pennellii introgression lines was analyzed. We determined phenotypes for physiological, metabolic, and growth related traits, including gas exchange and chlorophyll fluorescence parameters. Data analysis allowed the identification of 208 physiological and metabolic quantitative trait loci with 33 of these being associated to smaller intervals of the genomic regions, termed BINs. Eight BINs were identified that were associated with higher assimilation rates than the recurrent parent M82. Two and 10 genomic regions were related to shoot and root dry matter accumulation, respectively. Nine genomic regions were associated with starch levels, whereas 12 BINs were associated with the levels of other metabolites. Additionally, a comprehensive and detailed annotation of the genomic regions spanning these quantitative trait loci allowed us to identify 87 candidate genes that putatively control the investigated traits. We confirmed 8 of these at the level of variance in gene expression. Taken together, our results allowed the identification of candidate genes that most likely regulate photosynthesis, primary metabolism, and plant growth and as such provide new avenues for crop improvement.

Metabolic diversity in tuber tissues of native Chiloé potatoes and commercial cultivars of Solanum tuberosum ssp. tuberosum L.

INTRODUCTION: The native potatoes (Solanum tuberosum ssp. tuberosum L.) cultivated on Chiloé Island in southern Chile have great variability in terms of tuber shape, size, color and flavor. These traits have been preserved throughout generations due to the geographical position of Chiloé, as well as the different uses given by local farmers. OBJECTIVES: The present study aimed to investigate the diversity of metabolites in skin and pulp tissues of eleven native accessions of potatoes from Chile, and evaluate the metabolite associations between tuber tissues. METHODS: For a deeper characterization of these accessions, we performed a comprehensive metabolic study in skin and pulp tissues of tubers, 3 months after harvesting. Specific targeted quantification of metabolites using 96 well microplates, and high-performance liquid chromatography combined with non-targeted metabolite profiling by gas chromatography time-of-flight mass spectrometry were used in this study. RESULTS: We observed differential levels of antioxidant activity and phenolic compounds between skin and pulp compared to a common commercial cultivar (Desireé). In addition, we uncovered considerable metabolite variability between different tuber tissues and between native potatoes. Network correlation analysis revealed different metabolite associations among tuber tissues that indicate distinct associations between primary metabolite and anthocyanin levels, and antioxidant activity in skin and pulp tissues. Moreover, multivariate analysis lead to the grouping of native and commercial cultivars based on metabolites from both skin and pulp tissues. CONCLUSIONS: As well as providing important information to potato producers and breeding programs on the levels of health relevant phytochemicals and other abundant metabolites such as starch, proteins and amino acids, this study highlights the associations of different metabolites in tuber skins and pulp, indicating the need for distinct strategies for metabolic engineering in these tissues. Furthermore, this study shows that native Chilean potato accessions have great potential as a natural source of phytochemicals.

Understanding serine proteases implications on Leishmania spp lifecycle.

Serine proteases have significant functions over a broad range of relevant biological processes to the Leishmania spp lifecycle. Data gathered here present an update on the Leishmania spp serine proteases and the status of these enzymes as part of the parasite degradome. The serine protease genes (n = 26 to 28) in Leishmania spp, which encode proteins with a wide range of molecular masses (35 kDa-115 kDa), are described along with their degrees of chromosomal and allelic synteny. Amid 17 putative Leishmania spp serine proteases, only ∼18% were experimentally demonstrated, as: signal peptidases that remove the signal peptide from secretory pre-proteins, maturases of other proteins and with metacaspase-like activity. These enzymes include those of clans SB, SC and SF. Classical inhibitors of serine proteases are used as tools for the characterization and investigation of Leishmania spp. Endogenous serine protease inhibitors, which are ecotin-like, can act modulating host actions. However, crude or synthetic based-natural serine protease inhibitors, such as potato tuber extract, Stichodactyla helianthus protease inhibitor I, fukugetin and epoxy-α-lapachone act on parasitic serine proteases and are promising leishmanicidal agents. The functional interrelationship between serine proteases and other Leishmania spp proteins demonstrate essential functions of these enzymes in parasite physiology and therefore their value as targets for leishmaniasis treatment.

Antileishmanial Activity of 2-Methoxy-4H-spiro-[naphthalene-1,2'-oxiran]-4-one (Epoxymethoxy-lawsone): A Promising New Drug Candidate for Leishmaniasis Treatment.

Epoxymethoxylawsone is a naphthoquinone derivative promising as drug candidate for the treatment of leishmaniases. In the present work the effectiveness of epoxymethoxylawsone, and meglumine antimoniate on Leishmania (Leishmania) amazonensis parasites and on mice paw lesions of infected BALB/c mice was assessed. In an intracellular amastigotes assay, the half-maximal inhibitory concentration (IC50) value for epoxymethoxylawsone was slightly higher (1.7-fold) than that found for meglumine antimoniate. The efficacy of both drugs became more evident after 48 h of exposure when either the oxirane compound and reference drug reached 18-fold and 7.4-fold lower IC50 values (0.40 ± 0.001 µM and 0.60 ± 0.02 µM), respectively. Promastigotes were also affected by epoxymethoxylawsone after 24 h of incubation (IC50 = 45.45 ± 5.0 µM), but with IC50 6-fold higher than those found for intracellular amastigotes. Cytotoxicity analysis revealed that epoxymethoxylawsone (CC50 = 40.05 ± µM) has 1.7-fold higher effects than meglumine antimoniate (CC50 = 24.14 ± 2.6 µM). Treatment of the paw lesion in infected BALB/c mice with epoxymethoxy-lawsone led to a significant 27% reduction (p < 0.05) of the lesion size, for all administrated doses, compared to the control group. Lesion reduction was also detected after mice treatment with meglumine antimoniate, reaching 31.0% (0.23 mg of Sb(V)/Kg/day and 2.27 mg of Sb(V)/Kg/day) and 64.0% (22.7 mg of Sb(V)/Kg/day). In addition, mice lesion ultrastructural changes were evidenced in amastigotes. The set of data gathered here indicate that epoxymethoxylawsone has pronounced effects on parasites and merits furthering to the preclinical stage.

Exploring the unbinding of Leishmania (L.) amazonensis CPB derived-epitopes from H2 MHC class I proteins.

New strategies to control Leishmania disease demand an extensive knowledge about several aspects of infection including the understanding of its molecular events. In murine models, cysteine proteinase B from Leishmania amazonensis promotes regulation of immune response, and fragments from its C-terminus extension (cyspep) can play a decisive role in the host-parasite interaction. The interaction between cyspep-derived peptides and major histocompatibility complex (MHC) proteins is a crucial factor in Leishmania infections. Seven cyspep-derived peptides, previously identified as capable of interacting with H-2 (murine) MHC class I proteins, were studied in this work. We established a protocol to simulate the unbinding of these peptides from the cleft of H-2 receptors. From the simulations, we estimated the corresponding free energy of dissociation (ΔGd ) and described the molecular events that occur during the exit of peptides from the cleft. To test the reliability of this method, we first applied it to a calibration set of four crystallographic MHC/peptide complexes. Next, we explored the unbinding of the seven complexes mentioned above. Results were consistent with ΔGd values obtained from surface plasmon resonance (SPR) experiments. We also identified some of the primary interactions between peptides and H-2 receptors, and we detected three regions of influence for the interaction. This pattern was systematically observed for the peptides and helped determine a minimum distance for the real interaction between peptides and H-2 proteins occurring at ∼ 25 Å.

Natural genetic variation for morphological and molecular determinants of plant growth and yield.

The rates of increase in yield of the main commercial crops have been steadily falling in many areas worldwide. This generates concerns because there is a growing demand for plant biomass due to the increasing population. Plant yield should thus be improved in the context of climate change and decreasing natural resources. It is a major challenge which could be tackled by improving and/or altering light-use efficiency, CO2 uptake and fixation, primary metabolism, plant architecture and leaf morphology, and developmental plant processes. In this review, we discuss some of the traits which could lead to yield increase, with a focus on how natural genetic variation could be harnessed. Moreover, we provide insights for advancing our understanding of the molecular aspects governing plant growth and yield, and propose future avenues for improvement of crop yield. We also suggest that knowledge accumulated over the last decade in the field of molecular physiology should be integrated into new ideotypes.