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Papers by Leonardo Orlando
International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2000
Citrus trees in Uruguay are mainly grafted on trifoliate orange after the dissemination of citrus... more Citrus trees in Uruguay are mainly grafted on trifoliate orange after the dissemination of citrus tristeza virus in the 1940s. Trifoliate orange is very susceptible to citrus exocortis viroid (CEVd), but the occurrence of typical rootstock symptoms are difficult to find in citrus orchards in Uruguay. Several samples from orange and grapefruit trees grafted on trifoliate orange, with dwarfing and rootstock bark scaling were chosen, as well as asymptomatic trees to determine the presence of citrus viroids. The detection of viroids was done by biological assays on Etrog citron Arizona 861, herbaceous hosts and sequential polyacryamide gel electrophoresis. Several cDNA probes labeled with 32 P or digoxigenin were tested and were hybridized with samples from different isolates collected from citrus orchards. The cDNA probe was produced from a severe Uruguayan CEVd isolate (CEVd-Uy1) which had been previously cloned and sequenced. The following citrus viroids were found: CEVd, CVd-Ia, CVd-Ib, CVd-IIa, CVd-IIIa and CVd-IIIb; no CVd-IV was found in the samples collected. Several viroid combinations were found in the same trees. Characterization of the citrus viroids is an important step for the control and prevention of these agents in Uruguayan citrus industry that is 90% grafted on a susceptible rootstock.
Boletin Tecnico/Technical Bulletin
ABSTRACT
Aging, 2011
RasGRF1 is a Ras-guanine nucleotide exchange factor implicated in a variety of physiological proc... more RasGRF1 is a Ras-guanine nucleotide exchange factor implicated in a variety of physiological processes including learning and memory and glucose homeostasis. To determine the role of RASGRF1 in aging, lifespan and metabolic parameters were analyzed in aged RasGrf1(-/-) mice. We observed that mice deficient for RasGrf1(-/-) display an increase in average and most importantly, in maximal lifespan (20% higher than controls). This was not due to the role of Ras in cancer because tumor-free survival was also enhanced in these animals. Aged RasGrf1(-/-) displayed better motor coordination than control mice. Protection against oxidative stress was similarly preserved in old RasGrf1(-/-). IGF-I levels were lower in RasGrf1(-/-) than in controls. Furthermore, SIRT1 expression was increased in RasGrf1(-/-) animals. Consistent with this, the blood metabolomic profiles of RasGrf1-deficient mice resembled those observed in calorie-restricted animals. In addition, cardiac glucose consumption as d...
Frontiers in Bioscience, 2012
The Plant Journal, 2007
In many plants, photomorphogenesis is the default developmental program after seed germination, a... more In many plants, photomorphogenesis is the default developmental program after seed germination, and provides the key features that allow adaptation to light. This program is actively repressed if germination occurs in the absence of light, through a mechanism dependent on the E3 ubiquitin ligase activity that is encoded in Arabidopsis by COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1), which induces proteolytic degradation of transcription factors necessary for light-regulated development, such as HY5 (LONG HYPOCOTYL 5) and HYH (LONG HYPOCOTYL 5 HOMOLOG), and stabilization of transcription factors that promote skotomorphogenesis, such as PIF3 (PHYTOCHROME INTERACTING FACTOR 3). Seedlings deficient in gibberellin (GA) synthesis or signaling display a de-etiolated phenotype when grown in darkness, equivalent to the phenotype of cop1 mutants, which indicates that the switch between photo-and skotomorphogenesis is also under hormonal control. Here we provide evidence for the existence of crosstalk between GA and the COP1-mediated pathway, and identify HY5 and the PIF family as nodes of a regulatory network. This interaction occurs through distinct molecular mechanisms, based on the observation that GA signaling regulates protein stability of HY5, and the activity of PIF3.
PLoS ONE, 2011
Background: Although the AIB1 oncogene has an important role during the early phase of the cell c... more Background: Although the AIB1 oncogene has an important role during the early phase of the cell cycle as a coactivator of E2F1, little is known about its function during mitosis. Methodology/Principal Findings: Mitotic cells isolated by nocodazole treatment as well as by shake-off revealed a posttranslational modification occurring in AIB1 specifically during mitosis. This modification was sensitive to the treatment with phosphatase, suggesting its modification by phosphorylation. Using specific inhibitors and in vitro kinase assays we demonstrate that AIB1 is phosphorylated on Ser728 and Ser867 by Cdk1/cyclin B at the onset of mitosis and remains phosphorylated until exit from M phase. Differences in the sensitivity to phosphatase inhibitors suggest that PP1 mediates dephosphorylation of AIB1 at the end of mitosis. The phosphorylation of AIB1 during mitosis was not associated with ubiquitylation or degradation, as confirmed by western blotting and flow cytometry analysis. In addition, luciferase reporter assays showed that this phosphorylation did not alter the transcriptional properties of AIB1. Importantly, fluorescence microscopy and sub-cellular fractionation showed that AIB1 phosphorylation correlated with the exclusion from the condensed chromatin, thus preventing access to the promoters of AIB1-dependent genes. Phospho-specific antibodies developed against Ser728 further demonstrated the presence of phosphorylated AIB1 only in mitotic cells where it was localized preferentially in the periphery of the cell. Conclusions: Collectively, our results describe a new mechanism for the regulation of AIB1 during mitosis, whereby phosphorylation of AIB1 by Cdk1 correlates with the subcellular redistribution of AIB1 from a chromatin-associated state in interphase to a more peripheral localization during mitosis. At the exit of mitosis, AIB1 is dephosphorylated, presumably by PP1. This exclusion from chromatin during mitosis may represent a mechanism for governing the transcriptional activity of AIB1.
BOLETIN TECNICO DE CIENCIAS …
... Agronomía en Salto (EEFAS) una línea de selección y creación de portainjertos cítricos a trav... more ... Agronomía en Salto (EEFAS) una línea de selección y creación de portainjertos cítricos a través de polinizaciones de naranjas, pomelos y la mandarina Híbrida con ... Anderson (7) identificó por isoenzimas los plantines de origen cigótico de una población de citrumelo Swingle. ...
International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2000
Citrus trees in Uruguay are mainly grafted on trifoliate orange after the dissemination of citrus... more Citrus trees in Uruguay are mainly grafted on trifoliate orange after the dissemination of citrus tristeza virus in the 1940s. Trifoliate orange is very susceptible to citrus exocortis viroid (CEVd), but the occurrence of typical rootstock symptoms are difficult to find in citrus orchards in Uruguay. Several samples from orange and grapefruit trees grafted on trifoliate orange, with dwarfing and rootstock bark scaling were chosen, as well as asymptomatic trees to determine the presence of citrus viroids. The detection of viroids was done by biological assays on Etrog citron Arizona 861, herbaceous hosts and sequential polyacryamide gel electrophoresis. Several cDNA probes labeled with 32 P or digoxigenin were tested and were hybridized with samples from different isolates collected from citrus orchards. The cDNA probe was produced from a severe Uruguayan CEVd isolate (CEVd-Uy1) which had been previously cloned and sequenced. The following citrus viroids were found: CEVd, CVd-Ia, CVd-Ib, CVd-IIa, CVd-IIIa and CVd-IIIb; no CVd-IV was found in the samples collected. Several viroid combinations were found in the same trees. Characterization of the citrus viroids is an important step for the control and prevention of these agents in Uruguayan citrus industry that is 90% grafted on a susceptible rootstock.
Boletin Tecnico/Technical Bulletin
ABSTRACT
Aging, 2011
RasGRF1 is a Ras-guanine nucleotide exchange factor implicated in a variety of physiological proc... more RasGRF1 is a Ras-guanine nucleotide exchange factor implicated in a variety of physiological processes including learning and memory and glucose homeostasis. To determine the role of RASGRF1 in aging, lifespan and metabolic parameters were analyzed in aged RasGrf1(-/-) mice. We observed that mice deficient for RasGrf1(-/-) display an increase in average and most importantly, in maximal lifespan (20% higher than controls). This was not due to the role of Ras in cancer because tumor-free survival was also enhanced in these animals. Aged RasGrf1(-/-) displayed better motor coordination than control mice. Protection against oxidative stress was similarly preserved in old RasGrf1(-/-). IGF-I levels were lower in RasGrf1(-/-) than in controls. Furthermore, SIRT1 expression was increased in RasGrf1(-/-) animals. Consistent with this, the blood metabolomic profiles of RasGrf1-deficient mice resembled those observed in calorie-restricted animals. In addition, cardiac glucose consumption as d...
Frontiers in Bioscience, 2012
The Plant Journal, 2007
In many plants, photomorphogenesis is the default developmental program after seed germination, a... more In many plants, photomorphogenesis is the default developmental program after seed germination, and provides the key features that allow adaptation to light. This program is actively repressed if germination occurs in the absence of light, through a mechanism dependent on the E3 ubiquitin ligase activity that is encoded in Arabidopsis by COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1), which induces proteolytic degradation of transcription factors necessary for light-regulated development, such as HY5 (LONG HYPOCOTYL 5) and HYH (LONG HYPOCOTYL 5 HOMOLOG), and stabilization of transcription factors that promote skotomorphogenesis, such as PIF3 (PHYTOCHROME INTERACTING FACTOR 3). Seedlings deficient in gibberellin (GA) synthesis or signaling display a de-etiolated phenotype when grown in darkness, equivalent to the phenotype of cop1 mutants, which indicates that the switch between photo-and skotomorphogenesis is also under hormonal control. Here we provide evidence for the existence of crosstalk between GA and the COP1-mediated pathway, and identify HY5 and the PIF family as nodes of a regulatory network. This interaction occurs through distinct molecular mechanisms, based on the observation that GA signaling regulates protein stability of HY5, and the activity of PIF3.
PLoS ONE, 2011
Background: Although the AIB1 oncogene has an important role during the early phase of the cell c... more Background: Although the AIB1 oncogene has an important role during the early phase of the cell cycle as a coactivator of E2F1, little is known about its function during mitosis. Methodology/Principal Findings: Mitotic cells isolated by nocodazole treatment as well as by shake-off revealed a posttranslational modification occurring in AIB1 specifically during mitosis. This modification was sensitive to the treatment with phosphatase, suggesting its modification by phosphorylation. Using specific inhibitors and in vitro kinase assays we demonstrate that AIB1 is phosphorylated on Ser728 and Ser867 by Cdk1/cyclin B at the onset of mitosis and remains phosphorylated until exit from M phase. Differences in the sensitivity to phosphatase inhibitors suggest that PP1 mediates dephosphorylation of AIB1 at the end of mitosis. The phosphorylation of AIB1 during mitosis was not associated with ubiquitylation or degradation, as confirmed by western blotting and flow cytometry analysis. In addition, luciferase reporter assays showed that this phosphorylation did not alter the transcriptional properties of AIB1. Importantly, fluorescence microscopy and sub-cellular fractionation showed that AIB1 phosphorylation correlated with the exclusion from the condensed chromatin, thus preventing access to the promoters of AIB1-dependent genes. Phospho-specific antibodies developed against Ser728 further demonstrated the presence of phosphorylated AIB1 only in mitotic cells where it was localized preferentially in the periphery of the cell. Conclusions: Collectively, our results describe a new mechanism for the regulation of AIB1 during mitosis, whereby phosphorylation of AIB1 by Cdk1 correlates with the subcellular redistribution of AIB1 from a chromatin-associated state in interphase to a more peripheral localization during mitosis. At the exit of mitosis, AIB1 is dephosphorylated, presumably by PP1. This exclusion from chromatin during mitosis may represent a mechanism for governing the transcriptional activity of AIB1.
BOLETIN TECNICO DE CIENCIAS …
... Agronomía en Salto (EEFAS) una línea de selección y creación de portainjertos cítricos a trav... more ... Agronomía en Salto (EEFAS) una línea de selección y creación de portainjertos cítricos a través de polinizaciones de naranjas, pomelos y la mandarina Híbrida con ... Anderson (7) identificó por isoenzimas los plantines de origen cigótico de una población de citrumelo Swingle. ...