Gabriela Tais Saloma Soto - Academia.edu (original) (raw)

Papers by Gabriela Tais Saloma Soto

Microbial ecology, Jan 12, 2018

As other legume crops, alfalfa cultivation increases the emission of the greenhouse gas nitrous o... more As other legume crops, alfalfa cultivation increases the emission of the greenhouse gas nitrous oxide (N2O). Since legume-symbiotic nitrogen-fixing bacteria play a crucial role in this emission, it is important to understand the possible impacts of rhizobial domestication on the evolution of denitrification genes. In comparison with the genomes of non-commercial strains, those of commercial alfalfa inoculants exhibit low total genome size, low number of ORFs and high numbers of both frameshifted genes and pseudogenes, suggesting a dramatic loss of genes during bacterial domestication. Genomic analysis focused on denitrification genes revealed that commercial strains have perfectly conserved the nitrate (NAP), nitrite (NIR) and nitric (NOR) reductase clusters related to the production of N2O from nitrate but completely lost the nitrous oxide (NOS) reductase cluster (nosRZDFYLX genes) associated with the reduction of N2O to gas nitrogen. Based on these results, we propose future scree...

Journal of biotechnology, Jan 16, 2017

We here characterized the stress-tolerant alfalfa microsymbiont Sinorhizobium meliloti B401. B401... more We here characterized the stress-tolerant alfalfa microsymbiont Sinorhizobium meliloti B401. B401-treated plants showed high nitrogen fixation rates under humid and semiarid environments. The production of glycine betaine in isolated bacteroids positively correlated with low precipitation levels, suggesting that this compound acts as a critical osmoprotectant under field conditions. Genome analysis revealed that strain B401 contains alternative pathways for the biosynthesis and uptake of glycine betaine and its precursors. Such genomic information will offer substantial insight into the environmental physiology of this biotechnologically valuable nitrogen-fixing bacterium.

Journal of Molecular Evolution, 2017

Despite the vast screening for natural nitrogenfixing isolates by public and private consortia, n... more Despite the vast screening for natural nitrogenfixing isolates by public and private consortia, no significant progresses in the production of improved nitrogenfixing inoculants for alfalfa production have been made in the last years. Here, we present a comprehensive characterization of the nitrogen-fixing strain Ensifer meliloti B399 (originally named Rhizobium meliloti 102F34), probably the inoculant most widely used in alfalfa production since the 1960s. Complete nucleotide sequence and genome analysis of strain B399 showed that the three replicons present in this commercial strain and the model bacterium Ensifer meliloti 1021 are extremely similar to each other in terms of nucleotide identity and synteny conservation. In contrast to that observed in B399-treated plants, inoculation of plants with strain 1021 did not improve nitrogen content in different alfalfa cultivars under field conditions, suggesting that a small genomic divergence can drastically impact on the symbiotic phenotype. Therefore, in addition to the traditional screening of natural nitrogen-fixing isolates, the genome engineering of model strains could be an attractive strategy to improve nitrogen fixation in legume crops.

Seminario de graduacion ([licenciatura en odontologia])--Universidad de Costa Rica. Facultad de O... more Seminario de graduacion ([licenciatura en odontologia])--Universidad de Costa Rica. Facultad de Odontologia, 2005.

Revista Electronica De Desarrollo De Competencias, Jul 5, 2011

Esta investigacion pretende evaluar de forma individual y sintetica el efecto de las estrategias ... more Esta investigacion pretende evaluar de forma individual y sintetica el efecto de las estrategias metodologicas y evaluativas Mastery Learning y Evaluacion Autentica con Portafolios sobre el rendimiento academico en alumnos NB3, en la comuna de Valparaiso. Ello, para contribuir a una mejor calidad del aprendizaje de los alumnos en la asignatura comprension del medio natural. Bloom plantea como primer elemento la necesidad de crear un sistema educativo que lleve a la gran mayoria de los alumnos a alcanzar altos niveles de rendimiento academico, acortando la barrera de las diferencias entre los estudiantes a traves de la estrategia instruccional Mastery Learning. Para contrastar esta estrategia, se propuso la Evaluacion Autentica con Portafolios, con la finalidad de entregar un caracter de originalidad y de aporte de este estudio. La metodologia empleada es de caracter experimental, con grupos escogidos al azar, que tuviesen similitud en las variables al inicio de tratamiento. De ellos, uno se escogio como grupo control y tres fueron asignados como grupos experimentales, dos que aplicarian las estrategias por separado y uno en forma combinada. Se realizo un entrenamiento a cada uno de los profesores participantes, se elaboraron y validaron las pruebas, asi como tambien se seleccionaron las actividades y guias practicas para la clase. El analisis de los resultados muestra que no se encontraron tamanos de efecto significativos entre los grupos, luego de aplicadas las estrategias, por lo que no se puede asegurar que haya ocurrido algun tipo de incremento del rendimiento academico. Por esta razon y otras que se detallan al interior del texto, se ha recomendado el caracter de piloto de esta investigacion. Palabras claves: mastery learning – evaluacion autentica – comprension del medio natural.

Environmental Microbiology, 2016

SummaryA main goal of biological nitrogen fixation research has been to expand the nitrogen‐fixin... more SummaryA main goal of biological nitrogen fixation research has been to expand the nitrogen‐fixing ability to major cereal crops. In this work, we demonstrate the use of the efficient nitrogen‐fixing rhizobacterium Pseudomonas protegens Pf‐5 X940 as a chassis to engineer the transfer of nitrogen fixed by BNF to maize and wheat under non‐gnotobiotic conditions. Inoculation of maize and wheat with Pf‐5 X940 largely improved nitrogen content and biomass accumulation in both vegetative and reproductive tissues, and this beneficial effect was positively associated with high nitrogen fixation rates in roots. 15N isotope dilution analysis showed that maize and wheat plants obtained substantial amounts of fixed nitrogen from the atmosphere. Pf‐5 X940‐GFP‐tagged cells were always reisolated from the maize and wheat root surface but never from the inner root tissues. Confocal laser scanning microscopy confirmed root surface colonization of Pf‐5 X940‐GFP in wheat plants, and microcolonies were...

Biophysical Journal, 2016

Many plasma membrane channels form oligomeric assemblies, and heterooligomerization has been desc... more Many plasma membrane channels form oligomeric assemblies, and heterooligomerization has been described as a distinctive feature of some protein families. In the particular case of plant plasma membrane aquaporins (PIPs), PIP1 and PIP2 monomers interact to form heterotetramers. However, the biological properties of the different heterotetrameric configurations formed by PIP1 and PIP2 subunits have not been addressed yet. Upon coexpression of tandem PIP2-PIP1 dimers in Xenopus oocytes, we can address, for the first time to our knowledge, the functional properties of single heterotetrameric species having 2:2 stoichiometry. We have also coexpressed PIP2-PIP1 dimers with PIP1 and PIP2 monomers to experimentally investigate the localization and biological activity of each tetrameric assembly. Our results show that PIP2-PIP1 heterotetramers can assemble with 3:1, 1:3, or 2:2 stoichiometry, depending on PIP1 and PIP2 relative expression in the cell. All PIP2-PIP1 heterotetrameric species localize at the plasma membrane and present the same water transport capacity. Furthermore, the contribution of any heterotetrameric assembly to the total water transport through the plasma membrane doubles the contribution of PIP2 homotetramers. Our results also indicate that plasma membrane water transport can be modulated by the coexistence of different tetrameric species and by intracellular pH. Moreover, all the tetrameric species present similar cooperativity behavior for proton sensing. These findings throw light on the functional properties of PIP tetramers, showing that they have flexible stoichiometry dependent on the quantity of PIP1 and PIP2 molecules available. This represents, to our knowledge, a novel regulatory mechanism to adjust water transport across the plasma membrane.

Scientific Reports, 2016

The plastid organelle comprises a high proportion of nucleus-encoded proteins that were acquired ... more The plastid organelle comprises a high proportion of nucleus-encoded proteins that were acquired from different prokaryotic donors via independent horizontal gene transfers following its primary endosymbiotic origin. What forces drove the targeting of these alien proteins to the plastid remains an unresolved evolutionary question. To better understand this process we screened for suitable candidate proteins to recapitulate their prokaryote-to-eukaryote transition. Here we identify the ancient horizontal transfer of a bacterial polyphenol oxidase (PPO) gene to the nuclear genome of an early land plant ancestor and infer the possible mechanism behind the plastidial localization of the encoded enzyme. Arabidopsis plants expressing PPO versions either lacking or harbouring a plastid-targeting signal allowed examining fitness consequences associated with its subcellular localization. Markedly, a deleterious effect on plant growth was highly correlated with PPO activity only when producin...

AoB PLANTS, Jan 24, 2015

Recent advances at the molecular level are introducing a new scenario that needs to be integrated... more Recent advances at the molecular level are introducing a new scenario that needs to be integrated into the analysis of plant hydraulic properties. Although it is not yet clear to what extent this scenario alters the current proposal for the hydraulic circuit models, it introduces new insights when studying plants that are able to easily overcome water restrictions. In this context, our aim was to explore water adjustments in a halotolerant model (Beta vulgaris) by studying the coordination between the root in terms of root hydraulic conductivity (Lpr) and the shoot as reflected in the stomatal conductance (gs). The root water pathways were also analyzed in terms of root suberization (apoplastic barrier) and aquaporin transcript levels (cell-to-cell pathway). B. vulgaris showed the ability to rapidly lose (4h) and gain turgor (24 h) when submitted to salt stress (200 mM). The reduction profile observed in Lpr and gs was consistent with a coupled process. The tuning of the root water ...

FEMS Microbiology Letters, 2015

Phytophthora capsici is a virulent oomycete pathogen of many vegetable crops. Recently, it has be... more Phytophthora capsici is a virulent oomycete pathogen of many vegetable crops. Recently, it has been demonstrated that the recognition of the RXLR effector AVR3a1 of P. capsici (PcAVR3a1) triggers a hypersensitive response and plays a critical role in mediating non-host resistance. Here, we analyzed the occurrence of PcAVR3a1 in 57 isolates of P. capsici derived from globe squash, eggplant, tomato and bell pepper cocultivated in a small geographical area. The occurrence of PcAVR3a1 in environmental strains of P. capsici was confirmed by PCR in only 21 of these pathogen isolates. To understand the presence-absence pattern of PcAVR3a1 in environmental strains, the flanking region of this gene was sequenced. PcAVR3a1 was found within a genetic element that we named PcAVR3a1-GI (PcAVR3a1 genomic island). PcAVR3a1-GI was flanked by a 22-bp direct repeat, which is related to its site-specific recombination site. In addition to the PcAVR3a1 gene, PcAVR3a1-GI also encoded a phage integrase probably associated with the excision and integration of this mobile element. Exposure to plant induced the presence of an episomal circular intermediate of PcAVR3a1-GI, indicating that this mobile element is functional. Collectively, these findings provide evidence of PcAVR3a1 evolution via mobile elements in environmental strains of Phytophthora.

Journal of Molecular Evolution, 2015

The vast majority of Pseudomonas species are unable to fix atmospheric nitrogen. Although several... more The vast majority of Pseudomonas species are unable to fix atmospheric nitrogen. Although several studies have demonstrated that some strains belonging to the genus Pseudomonas sensu stricto do have the ability to fix nitrogen by the expression of horizontally acquired nitrogenase, little is known about the mechanisms of nitrogenase adaptation to the new bacterial host. Recently, we transferred the nitrogen fixation island from Pseudomonas stutzeri A1501 to the non-nitrogen-fixing bacterium Pseudomonas protegens Pf-5, and interestingly, the resulting recombinant strain Pf-5 X940 showed an uncommon phenotype of constitutive nitrogenase activity. Here, we integrated evolutionary and functional approaches to elucidate this unusual phenotype. Phylogenetic analysis showed that polyhydroxybutyrate (PHB) biosynthesis genes from natural nitrogen-fixing Pseudomonas strains have been acquired by horizontal transfer. Contrary to Pf-5 X940, its derived PHB-producing strain Pf-5 X940-PHB exhibited the inhibition of nitrogenase activity under nitrogen-excess conditions, and displayed the typical switch-on phenotype observed in natural nitrogen-fixing strains after nitrogen deficiency. This indicates a competition between PHB production and nitrogen fixation. Therefore, we propose that horizontal transfer of PHB biosynthesis genes could be an ancestral mechanism of regulation of horizontally acquired nitrogenases in the genus Pseudomonas.

Actualidades Investigativas en Educación, 2014

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FEMS microbiology letters, 2015

Snakin-1, a peptide produced by higher plants, has broad-spectrum antibiotic activity, inhibiting... more Snakin-1, a peptide produced by higher plants, has broad-spectrum antibiotic activity, inhibiting organisms ranging from Bacteria to Eukaryotes. However, the mode of action against target organisms is poorly understood. As a first step to elucidate the mechanism, we screened a mutation library of Pseudomonas fluorescens Pf-5 in LB and agar medium supplemented with alfalfa snakin-1 (MsSN1). We identified three biofilm formation-related Pseudomonas mutants that showed increased resistance to MsSN1. Genetic, physiological and bioinformatics analysis validated the results of the mutant screens, indicating that bacterial adhesion protein lapA is probably the target of MsSN1. Collectively, these findings suggest that snakin-1 acts on microbial adhesion properties.