Examinando por Autor "Meisel, Lee A."

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    Auxin transport inhibitors impair vesicle motility and actin cytoskeleton dynamics in diverse eukaryotes
    (National Academy of Sciences, 2008-03-18) Dhonukshe, Pankaj; Grigoriev, Ilya; Fischer, Rainer; Tominaga, Motoki; Robinson, David G.; Hasek, Jiri; Paciorek, Tomasz; Petrasek, Jan; Seifertova, Daniela; Tejos, Ricardo; Meisel, Lee A.; Zazimalova, Eva; Gadella, Theodorus W. J., Jr.; Stierhof, York-Dieter; Ueda, Takashi; Oiwa, Kazuhiro; Akhmanova, Anna; Brock, Roland; Spang, Anne; Friml, Jiri
    Many aspects of plant development, including patterning and tropisms, are largely dependent on the asymmetric distribution of the plant signaling molecule auxin. Auxin transport inhibitors (ATIs), which interfere with directional auxin transport, have been essential tools in formulating this concept. However, despite the use of ATIs in plant research for many decades, the mechanism of ATI action has remained largely elusive. Using real-time live-cell microscopy, we show here that prominent ATIs such as 2,3,5-triiodobenzoic acid (TIBA) and 2-(1-pyrenoyl) benzoic acid (PBA) inhibit vesicle trafficking in plant, yeast, and mammalian cells. Effects on micropinocytosis, rab5-labeled endosomal motility at the periphery of HeLa cells and on fibroblast mobility indicate that ATIs influence actin cytoskeleton. Visualization of actin cytoskeleton dynamics in plants, yeast, and mammalian cells show that ATIs stabilize actin. Conversely, stabilizing actin by chemical or genetic means interferes with endocytosis, vesicle motility, auxin transport, and plant development, including auxin transport-dependent processes. Our results show that a class of ATIs act as actin stabilizers and advocate that actin-dependent trafficking of auxin transport components participates in the mechanism of auxin transport. These studies also provide an example of how the common eukaryotic process of actin-based vesicle motility can fulfill a plant-specific physiological role.
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    Comparative EST transcript profiling of peach fruits under different post-harvest conditions reveals candidate genes associated with peach fruit quality
    (BMC, 2009-09-10) Vizoso, Paula; Meisel, Lee A.; Tittarelli, Andrés; Latorre, Mariano; Saba, Juan; Caroca, Rodrigo; Maldonado, Jonathan; Cambiazo, Veronica; Campos-Vargas, Reinaldo; Gonzalez, Mauricio; Orellana, Ariel; Silva, Herman
    Background: Cold storage is used to inhibit peach fruit ripening during shipment to distant markets. However, this cold storage can negatively affect the quality of the fruit when it is ripened, resulting in disorders such as wooliness, browning or leathering. In order to understand the individual and combined biological effects that factors such as cold storage and ripening have on the fruit and fruit quality, we have taken a comparative EST transcript profiling approach to identify genes that are differentially expressed in response to these factors. Results: We sequenced 50,625 Expressed Sequence Tags (ESTs) from peach mesocarp (Prunus persica O'Henry variety) stored at four different postharvest conditions. A total of 10,830 Unigenes (4,169 contigs and 6,661 singletons) were formed by assembling these ESTs. Additionally, a collection of 614 full-length and 1,109 putative full-length cDNA clones within flanking loxP recombination sites was created. Conclusion: Statistically analyzing the EST population, we have identified genes that are differentially expressed during ripening, in response to cold storage or the combined effects of cold storage and ripening. Pair-wise comparisons revealed 197 contigs with at least one significant difference in transcript abundance between at least two conditions. Gene expression profile analyses revealed that the contigs may be classified into 13 different clusters of gene expression patterns. These clusters include groups of contigs that increase or decrease transcript abundance during ripening, in response to cold or ripening plus cold. These analyses have enabled us to statistically identify novel genes and gene clusters that are differentially expressed in response to post-harvest factors such as long-term cold storage, ripening or a combination of these two factors. These differentially expressed genes reveal the complex biological processes that are associated with these factors, as well as a large number of putative gene families that may participate differentially in these processes. In particular, these analyzes suggest that woolly fruits lack the increased boost of metabolic processes necessary for ripening. Additionally, these results suggest that the mitochondria and plastids play a major role in these processes. The EST sequences and full-length cDNA clones developed in this work, combined with the large population of differentially expressed genes may serve as useful tools and markers that will enable the scientific community to better define the molecular processes that affect fruit quality in response to post-harvest conditions and the organelles that participate in these processes. © 2009 Vizoso et al; licensee BioMed Central Ltd.
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    El complejo Arp2/3 participa en el movimiento de cloroplastos en respuesta a luz azul y en la interacción cloroplastosactina en Arabidopsis thaliana
    (Universidad Andrés Bello, 2009) Rodríguez Rojas, Fernanda Jimena; Meisel, Lee A.; Facultad de Ciencias Biológicas; Escuela de Bioquímica
    Organismos fotosintéticos como las plantas han desarrollado diversos mecanismos con el fin de capturar y utilizar la energía solar para realizar complejos procesos metabólicos. Sin embargo, la alta intensidad de ciertas longitudes de onda de luz, como la luz azul ( 426-446 nm, 1 00 J..Lmoles/m -2 s-I) puede causar daños irreversibles a las estructuras intracelulares, tales como los organelos. Con el objetivo de evitar este daño por luz o "fotodaño", los cloroplastos han demostrado que pueden moverse a modo de alejamiento de esta fuente de luz, fenómeno conocido como movimiento de evasión. El movimiento de evasión de cloroplastos en respuesta a luz azul es un proceso conocido desde hace mucho tiempo, sin embargo, hasta el día de hoy se tiene muy poca información acerca de los factores moleculares que median este movimiento estimulado por luz. Con el objetivo de identificar el mecanismo molecular involucrado en el movimiento de evasión de cloroplastos en respuesta a luz, hemos implementado un ensayo de motilidad in vivo que nos permite visualizar el movimiento de cloroplastos en respuesta a luz azul en solo 15 segundos. Análisis en mutantes de Arabidopsis que han sido descritas previamente como mutantes que tienen alterada esta respuesta tales como photl, phot2 y chupl demostraron que este ensayo puede ser utilizado para identificar loci asociados al movimiento de evasión de cloroplastos. U san do este ensayo hemos podido demostrar que esta respuesta de evasión también está alterada en las mutantes que conforman el complejo nucleador de actina Arp2/3: arp3, arpc4 y arpc5; no así en las mutantes arp2 y arpc2. Adicionalmente un ensayo de interacción entre cloroplastos y filamentos de actina in vitro demostró que todos los loci pertenecientes al complejo Arp2/3 analizados en este trabajo están involucrados en esta interacción. Esto indica que aunque todos los componentes del complejo Arp2/3 son necesarios para mediar la adherencia de cloroplastos con los filamentos de actina, sólo algunos de estos componentes serian indispensables en la respuesta de evasión in vivo. Los resultados sugieren que el complejo Arp2/3 estaría participando en el movimiento de evasión de cloroplastos en respuesta a luz en Arabidopsis thaliana.
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    Multidimensional fluorescence microscopy of multiple organelles in Arabidopsis seedlings
    (BMC, 2008-05-19) Kato, Naohiro; Reynolds, Dexter; Brown, Matthew L.; Boisdore, Marietta; Fujikawa, Yukichi; Morales, Andrea; Meisel, Lee A.
    Background: The isolation of green fluorescent protein (GFP) and the development of spectral variants over the past decade have begun to reveal the dynamic nature of protein trafficking and organelle motility. In planta analyses of this dynamic process have typically been limited to only two organelles or proteins at a time in only a few cell types. Results: We generated a transgenic Arabidopsis plant that contains four spectrally different fluorescent proteins. Nuclei, plastids, mitochondria and plasma membranes were genetically tagged with cyan, red, yellow and green fluorescent proteins, respectively. In addition, methods to track nuclei, mitochondria and chloroplasts and quantify the interaction between these organelles at a submicron resolution were developed. These analyzes revealed that N-ethylmaleimide disrupts nuclear-mitochondrial but not nuclear-plastids interactions in root epidermal cells of live Arabidopsis seedlings. Conclusion: We developed a tool and associated methods for analyzing the complex dynamic of organelle-organelle interactions in real time in planta. Homozygous transgenic Arabidopsis (Kaleidocell) is available through Arabidopsis Biological Resource Center.
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    Proteomic analysis of peach fruit mesocarp softening and chilling injury using difference gel electrophoresis (DIGE)
    (BMC, 2010-01-18) Nilo, Ricardo; Saffie, Carlos; Lilley, Kathryn; Baeza-Yates, Ricardo; Cambiazo, Verónica; Campos-Vargas, Reinaldo; González, Mauricio; Meisel, Lee A.; Retamales, Julio; Silva, Herman; Orellana, Ariel
    Background: Peach fruit undergoes a rapid softening process that involves a number of metabolic changes. Storing fruit at low temperatures has been widely used to extend its postharvest life. However, this leads to undesired changes, such as mealiness and browning, which affect the quality of the fruit. In this study, a 2-D DIGE approach was designed to screen for differentially accumulated proteins in peach fruit during normal softening as well as under conditions that led to fruit chilling injury.Results: The analysis allowed us to identify 43 spots -representing about 18% of the total number analyzed- that show statistically significant changes. Thirty-nine of the proteins could be identified by mass spectrometry. Some of the proteins that changed during postharvest had been related to peach fruit ripening and cold stress in the past. However, we identified other proteins that had not been linked to these processes. A graphical display of the relationship between the differentially accumulated proteins was obtained using pairwise average-linkage cluster analysis and principal component analysis. Proteins such as endopolygalacturonase, catalase, NADP-dependent isocitrate dehydrogenase, pectin methylesterase and dehydrins were found to be very important for distinguishing between healthy and chill injured fruit. A categorization of the differentially accumulated proteins was performed using Gene Ontology annotation. The results showed that the 'response to stress', 'cellular homeostasis', 'metabolism of carbohydrates' and 'amino acid metabolism' biological processes were affected the most during the postharvest.Conclusions: Using a comparative proteomic approach with 2-D DIGE allowed us to identify proteins that showed stage-specific changes in their accumulation pattern. Several proteins that are related to response to stress, cellular homeostasis, cellular component organization and carbohydrate metabolism were detected as being differentially accumulated. Finally, a significant proportion of the proteins identified had not been associated with softening, cold storage or chilling injury-altered fruit before; thus, comparative proteomics has proven to be a valuable tool for understanding fruit softening and postharvest. © 2010 Nilo et al; licensee BioMed Central Ltd.