Pom1 regulates the assembly of Cdr2-Mid1 cortical nodes for robust spatial control of cytokinesis

Proper division plane positioning is essential to achieve faithful DNA segregation and to control daughter cell size, positioning, or fate within tissues. In Schizosaccharomyces pombe, division plane positioning is controlled positively by export of the division plane positioning factor Mid1/anillin from the nucleus and negatively by the Pom1/DYRK (dual-specificity tyrosine-regulated kinase) gradients emanating from cell tips. Pom1 restricts to the cell middle cortical cytokinetic ring precursor nodes organized by the SAD-like kinase Cdr2 and Mid1/anillin through an unknown mechanism. In this study, we show that Pom1 modulates Cdr2 association with membranes by phosphorylation of a basic region cooperating with the lipid-binding KA-1 domain. Pom1 also inhibits Cdr2 interaction with Mid1, reducing its clustering ability, possibly by down-regulation of Cdr2 kinase activity. We propose that the dual regulation exerted by Pom1 on Cdr2 prevents Cdr2 assembly into stable nodes in the cell tip region where Pom1 concentration is high, which ensures proper positioning of cytokinetic ring precursors at the cell geometrical center and robust and accurate division plane positioning

CONTRIBUTION A L'ETUDE DE GENES POTENTIELLEMENT IMPLIQUES DANS LE TRANSPORT DU NITRATE (CONSEQUENCES PHYSIOLOGIQUES DE LA DEREGULATION D'UN TRANSPORTEUR A HAUTE AFFINITE)

LE NITRATE EST LA PRINCIPALE SOURCE D'AZOTE POUR LA MAJORITE DES PLANTES ET SA CONCENTRATION DANS LA SOLUTION DU SOL PEUT FLUCTUER D'UN FACTEUR 3 OU 4. PAR CONSEQUENT, LES PLANTES ONT DEVELOPPE DES SYSTEMES DE TRANSPORT DU NITRATE QUI SONT REGULES PAR LES SOURCES AZOTES. CES SYSTEMES NECESSITENT DE L'ENERGIE ET IMPLIQUENT DES TRANSPORTEURS A FORTE ET A FAIBLE AFFINITE. LES GENES CODANT CES SYSTEMES DE TRANSPORT ONT ETE IDENTIFIES ET CLASSES EN DEUX FAMILLES BIEN DISTINCTES : NRT1 ET NRT2. LA PREMIERE PARTIE DE LA THESE EST CONSACREE A L'ETUDE D'UN DES MEMBRES DE LA FAMILLE NRT2 : LE GENE NPNRT2.1 ISOLE CHEZ NICOTIANA PLUMBAGINIFOLIA. L'EXPRESSION DE CE GENE S'EST REVELE ETRE INDUITE PAR DE FAIBLES CONCENTRATIONS EN NITRATE ET REPRIMEE PAR DES METABOLITES AZOTES REDUITS. L'EXPRESSION DE NPNRT2 EST EGALEMENT CORRELEE AVEC L'EXPRESSION DES AUTRES GENES DE LA VOIE D'ASSIMILATION DU NITRATE, AINSI QU'AVEC LE FLUX DE NITRATE PENETRANT DANS LA RACINE DE LA PLANTE. ENFIN, ET POUR LA PREMIERE FOIS, L'EXPRESSION D'UN GENE NRT2 A ETE LOCALISEE PRECISEMENT PAR HYBRIDATION IN SITU. LE GENE NPNRT2.1 EST EXPRIME DANS L'EPIDERME DES RACINES MATURES, LES PRIMORDIA ET LES POINTES RACINAIRES, AINSI QUE DANS LE MERISTEME APICAL DES PARTIES AERIENNES DE LA PLANTE. LA DEUXIEME PARTIE DE LA THESE EST CONSACREE A L'ETUDE DE DEUX MEMBRES DE LA FAMILLE NRT1 : LES GENES NPNRT1.1 ET NPNRT1.2. CES DEUX NOUVEAUX GENES PRESENTENT DES SEQUENCES PROTEIQUES TRES PROCHES, MAIS SONT EN REVANCHE REGULES DIFFEREMMENT SUIVANT LA SOURCE AZOTEE FOURNIE A LA PLANTE. L'EXPRESSION DE NPNRT1.2, LOCALISEE UNIQUEMENT DANS LA RACINE DE LA PLANTE, EST INDUITE PAR LE NITRATE. EN REVANCHE, CELLE DE NPNRT1.1, LOCALISEE DANS L'ENSEMBLE DES ORGANES DE LA PLANTE ET PLUS PARTICULIEREMENT DANS LES RACINES, EST CONSTITUTIVE. CES DEUX GENES CODERAIENT RESPECTIVEMENT LE ILATS ET LE CLATS. LA TROISIEME PARTIE DE LA THESE PRESENTE LES CONSEQUENCES PHYSIOLOGIQUES DE LA DEREGULATION DE L'EXPRESSION DU GENE NPNRT2.1 CHEZ UNE ESPECE MODELE (N. PLUMBAGINIFOLIA) ET CHEZ UNE ESPECE D'INTERET AGRONOMIQUE (SOLANUM TUBEROSUM). POUR CELA, LE GENE CHIMERIQUE CONSTITUE DE L'ADNC DE NPNRT2.1 A ETE PLACE SOUS LE CONTROLE DU PROMOTEUR 35S DU CAMV OU DU PROMOTEUR ROLD D'AGROBACTERIUM RHIZOGENES. CHEZ N. PLUMBAGINIFOLIA, L'ETUDE PHYSIOLOGIQUE DES PLANTES TRANSGENIQUES REVELE QUE LA SUREXPRESSION DE NPNRT2 EST EFFECTIVE UNIQUEMENT SUR FORTES CONCENTRATIONS NITRIQUES OU SUR AMMONIUM. CETTE AUGMENTATION DES ARNM NPNRT2, CORRELEE AVEC UNE HAUSSE DE L'INFLUX DE NO 3, N'ENGENDRE (I) AUCUNE DIFFERENCE PHENOTYPIQUE NOTABLE ET (II) AUCUNE MODIFICATION DES TENEURS EN NITRATE ENTRE LES PLANTES TRANSGENIQUES ET LES PLANTES SAUVAGES. DE PLUS, LE GENE CHIMERIQUE NE PRESENTE PLUS AUCUNE DES REGULATIONS TRANSCRIPTIONNELLES CONNUES POUR AFFECTER L'EXPRESSION DE NPNRT2. ENFIN, ET POUR LA PREMIERE FOIS, UNE REGULATION DE TYPE POST-TRANSCRIPTIONNEL EST MISE EN EVIDENCE POUR UN GENE DE LA FAMILLE NRT2. DES DONNEES PRELIMINAIRES CONCERNANT LA CARACTERISATION MOLECULAIRE DE POMME DE TERRE TRANSGENIQUES SONT EGALEMENT PRESENTEES DANS CETTE DERNIERE PARTIE.AMIENS-BU Sciences (800212103) / SudocSudocFranceF

Identification and expression analyses of two genes encoding putative low-affinity nitrate transporters from Nicotiana plumbaginifolia

30 ref.International audienc

Nitrate transport in plants: which gene and which control ?

55 ref., special issue: inorganic nitrogen assimilationInternational audienc

C-Terminal Anchoring of mid1p to Membranes Stabilizes Cytokinetic Ring Position in Early Mitosis in Fission Yeast

mid1p is a key factor for the central positioning of the cytokinetic ring in Schizosaccharomyces pombe. In interphase and early mitosis, mid1p forms a medial cortical band overlying the nucleus, which may represent a landmark for cytokinetic ring assembly. It compacts before anaphase into a tight ring with other cytokinetic ring components. We show here that mid1p binds to the medial cortex by at least two independent means. First, mid1p C-terminus association with the cortex requires a putative amphipathic helix adjacent to mid1p nuclear localization sequence (NLS), which is predicted to insert directly into the lipid bilayer. This association is stabilized by the polybasic NLS. mid1p mutated within the helix and the NLS forms abnormal filaments in early mitosis that are not properly anchored to the medial cortex. Misplaced rings assemble in late mitosis, indicating that mid1p C-terminus binding to membranes stabilizes cytokinetic ring position. Second, the N terminus of mid1p has the ability to associate faintly with the medial cortex and is sufficient to form tight rings. In addition, we show that mid1p oligomerizes. We propose that membrane-bound oligomers of mid1p assemble recruitment “platforms” for cytokinetic ring components at the medial cortex and stabilize the ring position during its compaction

Visualization and quantification of vesicle trafficking on a three-dimensional cytoskeleton network in living cells

International audienceRecent progress in biology and microscopy has made it possible to acquire multidimensional data on rapid cellular activities. Unfortunately, the data analysis needed to describe the observed biological process still remains a major bottleneck. We here present a novel method of studying membrane trafficking by monitoring vesicular structures moving along a three-dimensional cytoskeleton network. It allows the dynamics of such structures to be qualitatively and quantitatively investigated. Our tracking method uses kymogram analysis to extract the consistent part of the temporal information and to allow the meaningful representation of vesicle dynamics. A fully automatic extension of this method, together with a statistical tool for dynamic comparisons, allows the precise analysis and comparison of overall speed distributions and directions. It can handle typical complex situations, such as a dense set of vesicles moving at various velocities, fusing and dissociating with each other or with other cell compartments. The overall approach has been characterized and validated on synthetic data. We chose the Rab6A protein, a GTPase involved in the regulation of intracellular membrane trafficking, as a molecular model. The application of our method to GFP-Rab6A stable cells acquired using fast four-dimensional deconvolution video-microscopy gives considerable cellular dynamic information unreachable using other technique

Cell-Cycle Asynchrony Generates DNA Damage at Mitotic Entry in Polyploid Cells

International audienc

Spatial Control of Cytokinesis by Cdr2 Kinase and Mid1/Anillin Nuclear Export

International audienc