Structural insights into SARS-CoV-2 spike protein and its natural mutants found in Mexican population.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a newly emerged coronavirus responsible for coronavirus disease 2019 (COVID-19); it become a pandemic since March 2020. To date, there have been described three lineages of SARS-CoV-2 circulating worldwide, two of them are found among Mexican population, within these, we observed three mutations of spike (S) protein located at amino acids H49Y, D614G, and T573I. To understand if these mutations could affect the structural behavior of S protein of SARS-CoV-2, as well as the binding with S protein inhibitors (cepharanthine, nelfinavir, and hydroxychloroquine), molecular dynamic simulations and molecular docking were employed. It was found that these punctual mutations affect considerably the structural behavior of the S protein compared to wild type, which also affect the binding of its inhibitors into their respective binding site. Thus, further experimental studies are needed to explore if these affectations have an impact on drug-S protein binding and its possible clinical effect.

Iron responsive-like elements in the parasite Entamoeba histolytica.

In Entamoeba histolytica, iron modulates virulence and gene expression via unknown regulatory mechanisms. The existence of a posttranscriptional iron regulatory system parallel with the iron-responsive element (IRE)/iron regulatory protein (IRP) system in the protozoan Trichomonas vaginalis has recently been reported. Due to their evolutionary closeness and the importance of iron for growth and virulence in these protozoa, we hypothesized the existence of an IRE/IRP-like mechanism in E. histolytica. To determine the presence of IRE-like elements in some mRNAs from this parasite, we performed in silico analyses of the 5'- and 3'-UTRs of mRNAs encoding virulence factors and cytoskeleton, ribosomal and metabolism proteins. The Zuker mfold software predicted IRE-like secondary structures in 52 of the 135 mRNAs analysed. However, only nine structures shared sequence similarity with the apical loop sequence (CAGUGN) of the previously reported human IRE-ferritin, whereas the GUU/UUG protozoan-specific motif was detected in 23 stem-loop structures. A new motif, AUU/AUUU, was also observed in 23 structures, suggesting the possible existence of an amoeba-specific motif. Additionally, cross-linking and RNA electrophoretic mobility shift assays showed specific RNA-protein interactions, using as a model two amoebic IRE-like elements from iron-regulated mRNAs and HeLa, T. vaginalis and E. histolytica cytoplasmic proteins. Our data suggest the presence of a posttranscriptional iron regulatory IRE/IRP-like mechanism in E. histolytica.

Plant characterization of genetically modified maize hybrids MON-89Ø34-3 × MON-88Ø17-3, MON-89Ø34-3 × MON-ØØ6Ø3-6, and MON-ØØ6Ø3-6: alternatives for maize production in Mexico.

Environmental risk assessment (ERA) of genetically modified (GM) crops is a process to evaluate whether the biotechnology trait(s) in a GM crop may result in increased pest potential or harm to the environment. In this analysis, two GM insect-resistant (IR) herbicide-tolerant maize hybrids (MON-89Ø34-3 × MON-88Ø17-3 and MON-89Ø34-3 × MON-ØØ6Ø3-6) and one herbicide-tolerant GM hybrid (MON-ØØ6Ø3-6) were compared with conventional maize hybrids of similar genetic backgrounds. Two sets of studies, Experimental Phase and Pilot Phase, were conducted across five ecological regions (ecoregions) in Mexico during 2009-2013, and data were subject to meta-analysis. Results from the Experimental Phase studies, which were used for ERA, indicated that the three GM hybrids were not different from conventional maize for early stand count, days-to-silking, days-to-anthesis, root lodging, stalk lodging, or final stand count. Statistically significant differences were observed for seedling vigor, ear height, plant height, grain moisture, and grain yield, particularly in the IR hybrids; however, none of these phenotypic differences are expected to contribute to a biological or ecological change that would result in an increased pest potential or ecological risk when cultivating these GM hybrids. Overall, results from the Experimental Phase studies are consistent with those from other world regions, confirming that there are no additional risks compared to conventional maize. Results from Pilot Phase studies indicated that, compared to conventional maize hybrids, no differences were detected for the agronomic and phenotypic characteristics measured on the three GM maize hybrids, with the exception of grain moisture and grain yield in the IR hybrids. Since MON-89Ø34-3 × MON-88Ø17-3 and MON-89Ø34-3 × MON-ØØ6Ø3-6 confer resistance to target insect pests, they are an alternative for farmers in Mexico to protect the crop from insect damage. Additionally, the herbicide tolerance conferred by all three GM hybrids enables more cost-effective weed management.

Pollen-Mediated Gene Flow in Maize: Implications for Isolation Requirements and Coexistence in Mexico, the Center of Origin of Maize.

Mexico, the center of origin of maize (Zea mays L.), has taken actions to preserve the identity and diversity of maize landraces and wild relatives. Historically, spatial isolation has been used in seed production to maintain seed purity. Spatial isolation can also be a key component for a strategy to minimize pollen-mediated gene flow in Mexico between transgenic maize and sexually compatible plants of maize conventional hybrids, landraces, and wild relatives. The objective of this research was to generate field maize-to-maize outcrossing data to help guide coexistence discussions in Mexico. In this study, outcrossing rates were determined and modeled from eight locations in six northern states, which represent the most economically important areas for the cultivation of hybrid maize in Mexico. At each site, pollen source plots were planted with a yellow-kernel maize hybrid and surrounded by plots with a white-kernel conventional maize hybrid (pollen recipient) of the same maturity. Outcrossing rates were then quantified by assessing the number of yellow kernels harvested from white-kernel hybrid plots. The highest outcrossing values were observed near the pollen source (12.9% at 1 m distance). The outcrossing levels declined sharply to 4.6, 2.7, 1.4, 1.0, 0.9, 0.5, and 0.5% as the distance from the pollen source increased to 2, 4, 8, 12, 16, 20, and 25 m, respectively. At distances beyond 20 m outcrossing values at all locations were below 1%. These trends are consistent with studies conducted in other world regions. The results suggest that coexistence measures that have been implemented in other geographies, such as spatial isolation, would be successful in Mexico to minimize transgenic maize pollen flow to conventional maize hybrids, landraces and wild relatives.

Alimento para niños preparado con harinas de maíz de calidad proteínica y garbanzo extruidos / Weaning food from quality protein maize and chickpea extruded flours / Alimento para crianças preparado com farinhas de milho de qualidade proteínica e grãos-de-bico extrusado

El presente estudio tuvo tres objetivos: 1) Determinar la mejor combinación de harina de maíz de calidad proteínica extruido (HME) y harina de garbanzo extruido (HGE) para producir un alimento para niños de alta calidad proteínica y elevada aceptabilidad sensorial, 2) formular el alimento infantil tipo atole a partir de la mezcla HME/HGE optimizada, y 3) evaluar las propiedades nutricionales de la mezcla HME/HGE optimizada y del alimento. Se aplicó la metodología de superficie de respuesta para determinar la combinación óptima HME/HGE. La mejor combinación HME/HGE fue 21,2:78,8%; esta mezcla tuvo contenidos (en materia seca) de 20,07% de proteína, 5,70% de lípidos y 71,14% de carbohidratos; su perfil de aminoácidos esenciales cubrió satisfactoriamente los requerimientos para niños de 2-5 años de edad recomendados por FAO/WHO, excepto para triptófano. El alimento infantil tipo atole derivado de esta mezcla tuvo un contenido de proteína de 4,52%, que es 14,4% de la energía del alimento, adecuado para un alimento para niños. Cada 100g de alimento infantil aportan 6,3-12,6% y 23,8-34,8% del requerimiento diario de energía y proteína para niños y niñas de 1-8 años de edad. El alimento infantil tuvo 62,1% de digestibilidad de la proteína in vitro, C-PER de 1,93 y calificación entre "me gusta mucho" y "me gusta extremadamente" en una prueba hedónica para aceptabilidad general. Este alimento podría utilizarse como alimento soporte del crecimiento infantil.

The present study had three objectives: 1) To determine the best combination of quality extruded protein maize flour (EMF) and extruded chickpea flour (ECF) for producing a weaning food of high quality protein and high sensory acceptability, 2) to make a kind of infant food (atole) with an optimal EMF/ECF blend, and 3) to evaluate the nutritional properties of the optimized EMF/ECF mixture and the weaning food. Response surface methodology was applied to determine the optimal EMF/ECF combination. The best EMF/ECF combination was 21.2:78.8%. This mixture contained (in dry matter) 20.07% protein, 5.70% lipids and 71.14% carbohydrates; its essential amino acids (EAA) profile satisfactorily covered the requirements for children 2-5 years old recommended by FAO/WHO, except for tryptophan. The atole-type weaning food prepared with the optimized mixture had a protein content of 4.52%, which accounts for 14.4% of the supplied energy, suitable for a weaning food. Each 100g of the weaning food supply, respectively, 6.3-12.6% and 23.8-34.8% of the daily energy and protein requirements for children 1-8 years old. The weaning food had a 62.1% protein digestibility in vitro, a C-PER of 1.93, and was evaluated between "very liked" and "extremely liked" in a hedonic test for overall acceptability. This food could be used to support the growth of infants.

O presente estudo teve três objetivos: 1) Determinar a melhor combinação de farinha de milho de qualidade proteínica extrusado (HME) e farinha de grão-de-bico extrusado (HGE) para produzir um alimento para crianças de alta qualidade proteínica e elevada aceitabilidade sensorial, 2) formular o alimento infantil tipo mingau a partir da mistura HME/HGE otimizada, e 3) avaliar as propriedades nutricionais da mistura HME/HGE otimizada e do alimento. Aplicou-se a metodologia de superfície de resposta para determinar a combinação ótima HME/HGE. A melhor combinação HME/HGE 21,2:78,8%; esta mistura teve conteúdos (em matéria seca) de 20,07% de proteína, 5,70% de lipídios e 71,14% de carboidratos; seu perfil de aminoácidos essenciais cobriu satisfatoriamente os requerimentos para crianças de 2-5 anos de idade recomendados por FAO/WHO, exceto para triptófano. O alimento infantil tipo mingau derivado desta mistura teve um conteúdo de proteína de 4,52%, que é 14,4% da energia do alimento, adequado para um alimento para crianças. Cada 100g de alimento infantil aportam 6,3-12,6% e 23,8-34,8% do requerimento diário de energia e proteína para meninos e meninas 1-8 anos de idade. O alimento infantil teve 62,1% de digestibilidade da proteína in vitro, C-PER de 1,93 e qualificação entre "gosto muito" e "gosto demasiado" em uma prova hedônica para aceitabilidade general. Este alimento poderia utilizar-se como alimento suporte do crescimento infantil.