12 research outputs found
Modeling of a Gas Release from Underground Pipeline
The underground gas releases from buried pipelines can cause serious damage to the environment, properties, and population. This work aims at modelling the underground gas releases using a computational fluid dynamics numerical tool to allow the user to obtain a desired property (velocity, release rate, etc.) and visualize the behavior of a release. This was done through performing a sensitivity analysis on five crucial parameters that affect the results significantly, namely, the meshing size, soil particle diameter, turbulence model and the granular viscosity characterizing the soil. The resulting model was validated and used to delineate the boundaries between the different regimes corresponding to various release forces. The regimes are the resulting outcomes of the methaneâs flow which vary according to its release force ranging from migration through the soil, to uplift visible on the ground, till a crater formation. The pipeline burial depth was changed to investigate the effect of the change of burial height on the regime. The result was presented on a nomograph that allows to identify the regime corresponding to a given inlet force and pipeline burial depth, for an upward release orientation. The effect of the release orientation on the outcome was investigated for given pressures
CaractĂ©risation de protĂ©ines interagissant avec eIF4E, phosphorylĂ©es par TOR et modulant lâinitiation de la traduction coiffe-dĂ©pendante chez Arabidopsis
The target of rapamycin (TOR) is an evolutionarily conserved kinase that is a critical sensor of nutritional and cellular energy and a major regulator of cell growth. TOR controls cap-dependent translation initiation, in particular the assembly of the eIF4F complex, by modulating the activity of eIF4E-binding proteins (4E-BPs). In their unphosphorylated state 4E-BP proteins sequester eIF4E and repress translation. Upon phosphorylation by TOR, 4E-BPs have a low affinity binding to eIF4E and are replaced by eIF4G thus activating translation initiation. 4E-BPs have been discovered in yeast and mammals but remain to be obscure in plants. Here, we identified and characterized two Arabidopsis proteins termed TOR Regulatory Proteins (ToRPs 1 and 2) that display some characteristics of mammalian 4E-BPs. ToRP1 and ToRP2 contain a canonical eIF4E-binding motif (4E-BM) found in mammalian 4E-BPs and Arabidopsis eIF4G and eIFiso4G. ToRP1 interacts with eIF4E, and, surprisingly, the N-terminal HEAT domain of TOR in the yeast two-hybrid system. ToRP1 and ToRP2 are highly phosphorylated at several phosphorylation sites in TOR-dependent manner in planta. Two of these phosphorylation sites have been identified asâS49 and S89âtheir phosphorylation status modulates ToRP1 binding to eIF4E in the yeast two-hybrid system. In plant protoplasts, ToRP2 can function as translation repressor of mRNAs that are strictly cap-dependent. Our results suggest that ToRPs can specifically bind the Arabidopsis cap-binding proteins (eIF4E/eIFiso4E) and regulate translation initiation under the control of TORChez les mammifĂšres lâinitiation de la traduction et, plus particuliĂšrement, la formation du complexe eIF4F, est principalement rĂ©gulĂ©e par la protĂ©ine kinase TOR (Target of rapamycin). Cette voie de rĂ©gulation fait intervenir les protĂ©ines 4E-BP (eIF4E-binding proteins) dont lâactivitĂ© est modulĂ©e par la phosphorylation par TOR. Sous leur forme non-phosphorylĂ©e, les 4E-BP se lient au facteur dâinitiation eIF4E, empĂȘchent son recrutement dans le complexe eIF4F et inhibent ainsi lâinitiation de la traduction. PhosphorylĂ©es par TOR, les 4E-BP perdent leur affinitĂ© pour eIF4E et sont remplacĂ©es par eIF4G ce qui active la traduction. La rĂ©gulation de lâinitiation de la traduction par TOR via 4E-BP a Ă©tĂ© bien dĂ©crite dans plusieurs modĂšles eucaryotes, tels que la levure, les insectes et les mammifĂšres, mais reste encore obscure chez les plantes. Les recherches rĂ©alisĂ©es au cours de ma thĂšse ont permis lâidentification de deux protĂ©ines homologues de 4E-BP chez Arabidopsis. Ces protĂ©ines, que nous avons appelĂ©es ToRP1 et ToRP2 (TOR Regulatory Proteins), sont caractĂ©risĂ©es par la prĂ©sence dâun motif consensus indispensable pour la liaison Ă eIF4E, et qui existe chez les protĂ©ines 4E-BP des mammifĂšres ainsi que chez eIF4G et eIFiso4G dâArabidopsis. La protĂ©ine ToRP1 est capable dâinteragir spĂ©cifiquement avec eIF4E, mais aussi avec TOR via son extrĂ©mitĂ© N-terminale en systĂšme double-hybride de levure. ToRP1 et ToRP2 ont Ă©galement Ă©tĂ© caractĂ©risĂ©es comme Ă©tant des cibles directement phosphorylĂ©es par TOR chez Arabidopsis. Deux sĂ©rines, en position 49 et 89 dans la protĂ©ine ToRP1, ont Ă©tĂ© identifiĂ©es comme des sites potentiels de cette phosphorylation. De plus, lâĂ©tat de phosphorylation de ces sites affecte lâinteraction avec eIF4E en systĂšme double-hybride de levure. Par ailleurs, des plants dâArabidopsis dĂ©ficients en ToRP1 et ToRP2 renforcent la traduction strictement coiffe-dĂ©pendante de lâARNm CYCB1;1, alors que la surexpression de ToRP1 ou de ToRP2 rĂ©prime sa traduction. Ces rĂ©sultats suggĂšrent donc que les protĂ©ines ToRP, identifiĂ©es chez Arabidopsis, sont de nouvelles cibles directes de TOR, qui, par leur phosphorylation, rĂ©gule lâinitiation de la traduction coiffe-dĂ©pendante
Characterization of eIF4E-binding proteins that are phosphorylated by TOR and function in cap-dependent translation initiation in Arabidopsis
Chez les mammifĂšres lâinitiation de la traduction et, plus particuliĂšrement, la formation du complexe eIF4F, est principalement rĂ©gulĂ©e par la protĂ©ine kinase TOR (Target of rapamycin). Cette voie de rĂ©gulation fait intervenir les protĂ©ines 4E-BP (eIF4E-binding proteins) dont lâactivitĂ© est modulĂ©e par la phosphorylation par TOR. Sous leur forme non-phosphorylĂ©e, les 4E-BP se lient au facteur dâinitiation eIF4E, empĂȘchent son recrutement dans le complexe eIF4F et inhibent ainsi lâinitiation de la traduction. PhosphorylĂ©es par TOR, les 4E-BP perdent leur affinitĂ© pour eIF4E et sont remplacĂ©es par eIF4G ce qui active la traduction. La rĂ©gulation de lâinitiation de la traduction par TOR via 4E-BP a Ă©tĂ© bien dĂ©crite dans plusieurs modĂšles eucaryotes, tels que la levure, les insectes et les mammifĂšres, mais reste encore obscure chez les plantes. Les recherches rĂ©alisĂ©es au cours de ma thĂšse ont permis lâidentification de deux protĂ©ines homologues de 4E-BP chez Arabidopsis. Ces protĂ©ines, que nous avons appelĂ©es ToRP1 et ToRP2 (TOR Regulatory Proteins), sont caractĂ©risĂ©es par la prĂ©sence dâun motif consensus indispensable pour la liaison Ă eIF4E, et qui existe chez les protĂ©ines 4E-BP des mammifĂšres ainsi que chez eIF4G et eIFiso4G dâArabidopsis. La protĂ©ine ToRP1 est capable dâinteragir spĂ©cifiquement avec eIF4E, mais aussi avec TOR via son extrĂ©mitĂ© N-terminale en systĂšme double-hybride de levure. ToRP1 et ToRP2 ont Ă©galement Ă©tĂ© caractĂ©risĂ©es comme Ă©tant des cibles directement phosphorylĂ©es par TOR chez Arabidopsis. Deux sĂ©rines, en position 49 et 89 dans la protĂ©ine ToRP1, ont Ă©tĂ© identifiĂ©es comme des sites potentiels de cette phosphorylation. De plus, lâĂ©tat de phosphorylation de ces sites affecte lâinteraction avec eIF4E en systĂšme double-hybride de levure. Par ailleurs, des plants dâArabidopsis dĂ©ficients en ToRP1 et ToRP2 renforcent la traduction strictement coiffe-dĂ©pendante de lâARNm CYCB1;1, alors que la surexpression de ToRP1 ou de ToRP2 rĂ©prime sa traduction. Ces rĂ©sultats suggĂšrent donc que les protĂ©ines ToRP, identifiĂ©es chez Arabidopsis, sont de nouvelles cibles directes de TOR, qui, par leur phosphorylation, rĂ©gule lâinitiation de la traduction coiffe-dĂ©pendante.The target of rapamycin (TOR) is an evolutionarily conserved kinase that is a critical sensor of nutritional and cellular energy and a major regulator of cell growth. TOR controls cap-dependent translation initiation, in particular the assembly of the eIF4F complex, by modulating the activity of eIF4E-binding proteins (4E-BPs). In their unphosphorylated state 4E-BP proteins sequester eIF4E and repress translation. Upon phosphorylation by TOR, 4E-BPs have a low affinity binding to eIF4E and are replaced by eIF4G thus activating translation initiation. 4E-BPs have been discovered in yeast and mammals but remain to be obscure in plants. Here, we identified and characterized two Arabidopsis proteins termed TOR Regulatory Proteins (ToRPs 1 and 2) that display some characteristics of mammalian 4E-BPs. ToRP1 and ToRP2 contain a canonical eIF4E-binding motif (4E-BM) found in mammalian 4E-BPs and Arabidopsis eIF4G and eIFiso4G. ToRP1 interacts with eIF4E, and, surprisingly, the N-terminal HEAT domain of TOR in the yeast two-hybrid system. ToRP1 and ToRP2 are highly phosphorylated at several phosphorylation sites in TOR-dependent manner in planta. Two of these phosphorylation sites have been identified asâS49 and S89âtheir phosphorylation status modulates ToRP1 binding to eIF4E in the yeast two-hybrid system. In plant protoplasts, ToRP2 can function as translation repressor of mRNAs that are strictly cap-dependent. Our results suggest that ToRPs can specifically bind the Arabidopsis cap-binding proteins (eIF4E/eIFiso4E) and regulate translation initiation under the control of TO
Functional analogs of mammalian 4E-BPs reveal a role for TOR in global plant translation
Summary: Mammalian/mechanistic target of rapamycin (mTOR) regulates global protein synthesis through inactivation of eIF4E-binding proteins (m4E-BPs) in response to nutrient and energy availability. Until now, 4E-BPs have been considered as metazoan inventions, and how target of rapamycin (TOR) controls cap-dependent translation initiation in plants remains obscure. Here, we present short unstructured 4E-BP-like Arabidopsis proteins (4EBP1/4EBP2) that are non-homologous to m4E-BPs except for the eIF4E-binding motif and TOR phosphorylation sites. Unphosphorylated 4EBPs exhibit strong affinity toward eIF4Es and can inhibit formation of the cap-binding complex. Upon TOR activation, 4EBPs are phosphorylated, probably when bound directly to TOR, and likely relocated to ribosomes. 4EBPs can suppress a distinct set of mRNAs; 4EBP2 predominantly inhibits translation of core cell-cycle regulators CycB1;1 and CycD1;1, whereas 4EBP1 interferes with chlorophyll biosynthesis. Accordingly, 4EBP2 overexpression halts early seedling development, which is overcome by induction of Glc/Suc-TOR signaling. Thus, TOR regulates cap-dependent translation initiation by inactivating atypical 4EBPs in plants
Phosphorylation of a reinitiation supporting protein, RISP, determines its function in translation reinitiation
International audienc
Viral protein suppresses oxidative burst and salicylic acid-dependent autophagy and facilitates bacterial growth on virus-infected plants
Virus interactions with plant silencing and innate immunity pathways can potentially alter the susceptibility of virus-infected plants to secondary infections with nonviral pathogens. We found that Arabidopsis plants infected with Cauliflower mosaic virus (CaMV) or transgenic for CaMV silencing suppressor P6 exhibit increased susceptibility to Pseudomonas syringae pv. tomato (Pst) and allow robust growth of the Pst mutant hrcC-, which cannot deploy effectors to suppress innate immunity. The impaired antibacterial defense correlated with the suppressed oxidative burst, reduced accumulation of the defense hormone salicylic acid (SA) and diminished SA-dependent autophagy. The viral protein domain required for suppression of these plant defense responses is dispensable for silencing suppression but essential for binding and activation of the plant target-of-rapamycin (TOR) kinase which, in its active state, blocks cellular autophagy and promotes CaMV translation. Our findings imply that CaMV P6 is a versatile viral effector suppressing both silencing and innate immunity. P6-mediated suppression of oxidative burst and SA-dependent autophagy may predispose CaMV-infected plants to bacterial infection
Viral protein suppresses oxidative burst and salicylic acidâdependent autophagy and facilitates bacterial growth on virusâinfected plants
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