Análisis del comportamiento de un motor encendido por compresión funcionando con el sistema dual diésel-gas natural

El objetivo de este trabajo fue evaluar cuantitativamente la utilización de gas natural comprimido (GNC) proveniente del Chaco paraguayo, en la operación de motores diésel en forma dual, haciendo un mínimo de modificaciones en los mismos. Para el uso de GNC, se añadió, una cámara de mezcla de gas en el múltiple de admisión de aire y un kit de conversión (consta de un regulador de presión de gas y el sistema electrónico de conmutación del regulador) a un motor diésel bicilindro acoplado a un banco de pruebas. En el sistema dual, el motor mostró un rendimiento térmico similar en comparación con el funcionamiento a diésel exclusivo para cargas medias a elevadas y menores rendimientos a bajas cargas. El análisis de costes mostró viabilidad económica en ciertos rangos de sustitución, resultando importante para la promoción de la explotación del gas natural en Paraguay, considerando que el 100% de los derivados del petróleo son importados.The objective of this work is to quantitatively evaluate the use of Compressed Natural Gas (CNG) which comes from the Paraguayan Chaco, in the operation of diesel engines in a dual form, making a minimum of modifications in them. For the use of CNG, a cross-flow gas mixing chamber was added to the air inlet manifold, a conversion kit (consisting of a gas pressure regulator and the electronic regulator switching system), to a Diesel engine coupled to a test bank. In the dual system, the engine showed a similar thermal performance compared to the exclusive diesel operation for medium to high loads and lower performance at low loads. The analysis of costs showed economic viability in certain ranges of substitution, being important for the promotion of the exploitation of the natural gas in Paraguay, considering that 100% of the oil derivatives are imported.Fil: Sebriano Paredes, César Jesús. Universidad Nacional de Itapúa (Paraguay).Fil: Cano Coscia, Eugenio José. Universidad Nacional de Itapúa (Paraguay).Fil: Riveros Saavedra, Waldy Aníbal. Universidad Nacional de Itapúa (Paraguay)

Expression QTL (eQTLs) Analyses Reveal Candidate Genes Associated With Fruit Flesh Softening Rate in Peach [Prunus persica (L.) Batsch]

Indexación: ScopusSignificant differences in softening rate have been reported between melting flesh in peach and nectarine varieties. This trait seems to be controlled by several genes. We aimed to identify candidate genes involved in fruit softening rate by integrating quantitative trait loci (QTL) and expression QTL (eQTL) analyses, comparing siblings with contrasting softening rates. We used a segregating population derived from nectarine cv. ‘Venus’ selfing, which was phenotyped for softening rate during three seasons. Six siblings with high (HSR) and six with low softening rate (LSR) were sequenced using RNA-Seq. A group of 5,041 differentially expressed genes was identified. Also, we found a QTL with a LOD (logarithm of odds) score of 9.7 on LG4 in all analyzed seasons. Furthermore, we detected 1,062 eQTLs, of which 133 were found co-localizing with the identified QTL. Gene Ontology (GO) analysis showed ‘Response to auxin’ as one the main over-represented categories. Our findings suggest over-expression of auxin biosynthetic related genes in the HSR group, which implies a higher expression and/or accumulation of auxin, thereby triggering fast softening. Conversely, the LSR phenotype might be explained by an altered auxin-homeostasis associated with low auxin levels. This work will contribute to unraveling the genetic mechanisms responsible for the softening rate in peaches and nectarines and lead to the development of molecular markers. © Copyright © 2019 Carrasco-Valenzuela, Muñoz-Espinoza, Riveros, Pedreschi, Arús, Campos-Vargas and Meneses.https://www.frontiersin.org/articles/10.3389/fpls.2019.01581/ful

Identification of DNA Methylation and Transcriptomic Profiles Associated With Fruit Mealiness in Prunus persica (L.) Batsch

Peach (Prunus persica) fruits have a fast ripening process and a shelf-life of days, presenting a challenge for long-distance consuming markets. To prolong shelf-life, peach fruits are stored at low temperatures (0 to 7 °C) for at least two weeks, which can lead to the development of mealiness, a physiological disorder that reduces fruit quality and decreases consumer acceptance. Several studies have been made to understand this disorder, however, the molecular mechanisms underlying mealiness are not fully understood. Epigenetic factors, such as DNA methylation, modulate gene expression according to the genetic background and environmental conditions. In this sense, the aim of this work was to identify differentially methylated regions (DMRs) that could affect gene expression in contrasting individuals for mealiness. Peach flesh was studied at harvest time (E1 stage) and after cold storage (E3 stage) for 30 days. The distribution of DNA methylations within the eight chromosomes of P. persica showed higher methylation levels in pericentromeric regions and most differences between mealy and normal fruits were at Chr1, Chr4, and Chr8. Notably, differences in Chr4 co-localized with previous QTLs associated with mealiness. Additionally, the number of DMRs was higher in CHH cytosines of normal and mealy fruits at E3; however, most DMRs were attributed to mealy fruits from E1, increasing at E3. From RNA-Seq data, we observed that differentially expressed genes (DEGs) between normal and mealy fruits were associated with ethylene signaling, cell wall modification, lipid metabolism, oxidative stress and iron homeostasis. When integrating the annotation of DMRs and DEGs, we identified a CYP450 82A and an UDP-ARABINOSE 4 EPIMERASE 1 gene that were downregulated and hypermethylated in mealy fruits, coinciding with the co-localization of a transposable element (TE). Altogether, this study indicates that genetic differences between tolerant and susceptible individuals is predominantly affecting epigenetic regulation over gene expression, which could contribute to a metabolic alteration from earlier stages of development, resulting in mealiness at later stages. Finally, this epigenetic mark should be further studied for the development of new molecular tools in support of breeding programs

Main Molecular Pathways Associated with Copper Tolerance Response in <i>Imperata cylindrica</i> by de novo Transcriptome Assembly

The metallophyte Imperata cylindrica inhabits copper (Cu) polluted soils in large areas from Central Chile. Here, we subjected clonal vegetative plantlets to 300 mg Cu kg−1 of substrate for 21 days to identify the main molecular pathways involved in the response to Cu stress. Transcriptomic analyses were performed for shoots and roots, with and without Cu supply. RNA-Seq and de novo transcriptome assembly were performed to identify the gene response associated with molecular mechanisms of Cu tolerance in I. cylindrica. De novo transcriptome revealed a total of 200,521 transcripts (1777 bp) comprising ~91% complete ultra-conserved genes in the eukaryote and Plantae database. The differentially expressed genes (DEGs) in roots were 7386, with 3558 of them being up-regulated and the other 3828 down-regulated. The transcriptome response in shoots was significantly less, showing only 13 up-regulated and 23 down-regulated genes. Interestingly, DEGs mainly related with actin and cytoskeleton formation, and to a minor degree, some DEGs associated with metal transporters and superoxide dismutase activity in root tissues were found. These transcriptomic results suggest that cytoskeleton could be acting as a mechanism of Cu-binding in the root, resulting in a high Cu tolerance response in this metallophyte, which deserve to be analyzed ultra-structurally. Our study contributes to reinforcing the potential of I. cylindrica as a candidate plant species to be used as a phytoremediation agent in Cu-contaminated environments

Response mechanisms of “Hass” avocado to sequential 1–methylcyclopropene applications at different maturity stages during cold storage

1–Methylcyclopropene (1–MCP) is used for extending the postharvest life of the avocado during storage. In this study, fruits from two maturity stages at harvest were used: low dry matter (20–23%) and high dry matter (27%), combined with 1–MCP at different times after harvest, i.e., 0, 7, 14, and 21 d at 5 °C, to identify the threshold of the ethylene inhibition response in “Hass” avocado. Our results showed changes in ethylene production rates and transcript accumulation of genes involved in ethylene metabolism when measured at harvest and during storage. 1–MCP treated fruit up to 14 d of storage showed similar values of firmness and skin color as fruit treated at harvest time. In contrast, when the application was performed after 21 d, the fruit showed ripening attributes like those of the untreated ones. We performed a transcriptomic analysis, to further understand the lack of response to 1-MCP at 21 d of storage. Results showed an increase of transcripts involved in the ‘response to ethylene’. All genes evaluated showed similar expression profiles induced by cold storage time, with a peak at 21 d of storage and an increased softening of the fruit and peel color. Our results should help to understand the molecular mechanisms of the avocado ripening process.Facultad de Ciencias Agrarias y Forestale

Expression QTL (eQTLs) Analyses Reveal Candidate Genes Associated With Fruit Flesh Softening Rate in Peach [Prunus persica (L.) Batsch]

Significant differences in softening rate have been reported between melting flesh in peach and nectarine varieties. This trait seems to be controlled by several genes. We aimed to identify candidate genes involved in fruit softening rate by integrating quantitative trait loci (QTL) and expression QTL (eQTL) analyses, comparing siblings with contrasting softening rates. We used a segregating population derived from nectarine cv. 'Venus' selfing, which was phenotyped for softening rate during three seasons. Six siblings with high (HSR) and six with low softening rate (LSR) were sequenced using RNA-Seq. A group of 5,041 differentially expressed genes was identified. Also, we found a QTL with a LOD (logarithm of odds) score of 9.7 on LG4 in all analyzed seasons. Furthermore, we detected 1,062 eQTLs, of which 133 were found co-localizing with the identified QTL. Gene Ontology (GO) analysis showed 'Response to auxin' as one the main over-represented categories. Our findings suggest over-expression of auxin biosynthetic related genes in the HSR group, which implies a higher expression and/or accumulation of auxin, thereby triggering fast softening. Conversely, the LSR phenotype might be explained by an altered auxin-homeostasis associated with low auxin levels. This work will contribute to unraveling the genetic mechanisms responsible for the softening rate in peaches and nectarines and lead to the development of molecular markers