Regulation of Op18 during Spindle Assembly in Xenopus Egg Extracts

Oncoprotein 18 (Op18) is a microtubule-destabilizing protein that is negatively regulated by phosphorylation. To evaluate the role of the three Op18 phosphorylation sites in Xenopus (Ser 16, 25, and 39), we added wild-type Op18, a nonphosphorylatable triple Ser to Ala mutant (Op18-AAA), and to mimic phosphorylation, a triple Ser to Glu mutant (Op18-EEE) to egg extracts and monitored spindle assembly. Op18-AAA dramatically decreased microtubule length and density, while Op18-EEE did not significantly affect spindle microtubules. Affinity chromatography with these proteins revealed that the microtubule-destabilizing activity correlated with the ability of Op18 to bind tubulin. Since hyperphosphorylation of Op18 is observed upon addition of mitotic chromatin to extracts, we reasoned that chromatin-associated proteins might play a role in Op18 regulation. We have performed a preliminary characterization of the chromatin proteins recruited to DNA beads, and identified the Xenopus polo-like kinase Plx1 as a chromatin-associated kinase that regulates Op18 phosphorylation. Depletion of Plx1 inhibits chromatin-induced Op18 hyperphosphorylation and spindle assembly in extracts. Therefore, Plx1 may promote microtubule stabilization and spindle assembly by inhibiting Op18

Prime movers : mechanochemistry of mitotic kinesins

Mitotic spindles are self-organizing protein machines that harness teams of multiple force generators to drive chromosome segregation. Kinesins are key members of these force-generating teams. Different kinesins walk directionally along dynamic microtubules, anchor, crosslink, align and sort microtubules into polarized bundles, and influence microtubule dynamics by interacting with microtubule tips. The mechanochemical mechanisms of these kinesins are specialized to enable each type to make a specific contribution to spindle self-organization and chromosome segregation

Tubulin-binding dibenz[c,e]oxepines: Part 2 Structural variation and biological evaluation as tumour vasculature disrupting agents

5,7-Dihydro-3,9,10,11-tetramethoxybenz[c,e]oxepin-4-ol 1, prepared from a dibenzyl ether precursor via Pd-catalysed intramolecular direct arylation, possesses broad-spectrum in vitro cytotoxicity towards various tumour cell lines, and induces vascular shutdown, necrosis and growth delay in tumour xenografts in mice at sub-toxic doses. The biological properties of 1 and related compounds can be attributed to their ability to inhibit microtubule assembly at the micromolar level, by binding reversibly to the same site of the tubulin αβ-heterodimer as colchicine 2 and the allocolchinol, N-acetylcolchinol 4

Biologie de la reproduction et diversité génétique et spatiale de deux espèces du genre Vanilla (Orchidaceae) du sud-ouest de l'océan Indien : V. humblotii et V. roscheri. Implications pour leur conservation

Face aux menaces des grands bouleversements environnementaux, le développement des approches combinées de la biologie de la reproduction et de la diversité génétique des espèces végétales s'avère être essentiel pour améliorer et optimiser la conservation de la biodiversité. Le sud-ouest de l'océan Indien abrite un groupe monophylétique de sept espèces aphylles du genre Vanilla Plum Ex Miller (Orchidaceae, Vanilloideae), dont V. humblotii Rchb. f. et V. roscheri Rchb. f.endémiques de l'archipel des Comores et du sud-est africain respectivement. Leurs feuilles vestigiales, semblables à des écailles, leurs confèrent une adaptation aux forêts tropicales sèches mais elles peuvent se retrouver également en forêt tropicale mésophile. Dans un contexte où l'espèce cultivée du genre Vanilla, V. planifolia G. Jackson à l'origine de la gousse de vanille, est particulièrement vulnérable aux agressions biotique et abiotique à cause d'une base génétique extrêmement réduite dans les cultures, la plasticité écologique des vanilliers aphylles est un caractère majeur potentiellement exploitable pour améliorer l'espèce cultivée. Des missions de prospections ont permis d'identifier et d'échantillonner les populations naturelles de V.humblotii à Mayotte (Archipel Des Comores) et de V. roscheri sur les berges du lac Sibaya dans le KwaZuluNatal (Afrique Du Sud). Une étude de leur biologie de la reproduction, associant une évaluation des systèmes d'incompatibilité, des régimes de reproduction et une identification des pollinisateurs a été réalisée chez les deux espèces. En parallèle, des marqueurs microsatellites ont été développés à partir de ces espèces pour évaluer la diversité génétique de leurs populations, l'influence des modes et des régimes de reproduction sur la structuration génétique et spatiale des espèces à différentes échelles. A Mayotte, la fragmentation des populations naturelles de V. humblotii a entrainé la perte de diversité allélique mesurée dans de nombreuses populations de taille réduite. Néanmoins, le caractère longévif de V. humblotii, favorisé par la reproduction végétative, a permis de maintenir une diversité génotypique élevée (G/N = 0.88) et de limiter les impacts délétères de la réduction drastique des tailles de population. Bien que l'architecture phalanx de la clonalité soit majoritairement responsable des autocorrélations génétique et spatiale à petite distance (<10m), la dispersion des graines supérieure à la dispersion du pollen limite les possibilités de croisements consanguins par geitonogamie. Cependant, l'étude approfondie de la reproduction a révélé un faible taux de fructification naturelle (0.8%) et la perte quasi-totale des interactions plante-pollinisateurs, bien qu'une femelle abeille allodapine, Allodapeobscuripennis Strand (Apidae, Xylocopinae, Allodapini), et une femelle souimanga, Nectarinia coquerelli(Passeriformes, Nectariniidae), aient été observées comme visiteurs des fleurs de V. humblotii.En Afrique Du Sud, l'analyse génétique des populations de V. roscheri révèle un cas sans précédent de perte totale de diversité génétique avec une homozygotie généralisée à l'ensemble des marqueurs microsatellites. En limite d'aire de répartition de l'espèce en Afrique Du Sud, les populations ont probablement subi un fort goulot d'étranglement (par migration ou fragmentation de population) suivie d'une importante consanguinisation. En revanche, le taux de fructification moyen est le plus élevé (26.3%)jamais rapporté pour une espèce allogame du genre Vanilla, avec de nombreux visiteurs des fleursassociés à des mouvements de pollen, dont notamment, deux abeilles allodapines femelles (Allodapulavariegata Smith et Allodape rufogastra Lepeletier et Serville (Apidae, Xylocopinae, Allodapini)), et une abeille anthophorine femelle (Apidae, Apinae, Anthophorini sp), caractérisées comme étant les principaux pollinisateurs de V. roscheri.Les modèles étudiés soulignent la complémentarité des approches génétique et écologi

The Caenorhabditis elegans microtubule minus-end binding homolog PTRN-1 stabilizes synapses and neurites

Microtubule dynamics facilitate neurite growth and establish morphology, but the role of minus-end binding proteins in these processes is largely unexplored. CAMSAP homologs associate with microtubule minus-ends, and are important for the stability of epithelial cell adhesions. In this study, we report morphological defects in neurons and neuromuscular defects in mutants of the C. elegans CAMSAP, ptrn-1. Mechanosensory neurons initially extend wild-type neurites, and subsequently remodel by overextending neurites and retracting synaptic branches and presynaptic varicosities. This neuronal remodeling can be activated by mutations known to alter microtubules, and depends on a functioning DLK-1 MAP kinase pathway. We found that PTRN-1 localizes to both neurites and synapses, and our results suggest that alterations of microtubule structures caused by loss of PTRN-1 function activates a remodeling program leading to changes in neurite morphology. We propose a model whereby minus-end microtubule stabilization mediated by a functional PTRN-1 is necessary for morphological maintenance of neurons. DOI: http://dx.doi.org/10.7554/eLife.01637.00

Case Study of Impact Evaluation of Agrivoltaic Structure Sizing on Water Availability for Wheat: Microclimate Simulations for Agrivoltaics System Performance Assessment

Agrivoltaic (AV) Systems are a new solution for cropping conditions improvement by mitigating extreme weather conditions. Indeed, AV Systems affect microclimate, notably Air Temperature, Irradiance or Evapotranspiration that determines Soil Water Availability. To evaluate crop water stress protection and ensure optimized AV Systems sizing, a methodology was developed using a microclimate simulation tool. This paper presents a case study of Wheat focused on Water Availability, from a project located near Orléans, Center France. The methodology uses Irradiance Simulations at crop level by AGRISOLEO software, which has been parameterized with the structures sizing under study and a panel steering algorithm adapted to wheat phenology. The results are used for evapotranspiration modelling following the FAO-56 Penman-Monteith equation. For this case study, results showed that AV Systems under test reduced irradiance up to 40%. This effect may be reduced up to 17% by controlling the panels rotation angle to maximize irradiance during crop’s key development stages. Furthermore, AV Systems reduced Water Stress up to 48%. Microclimate simulation tool demonstrated possibility to assess AV Systems sizing impact on irradiance received by crop and Water Stress protection. Moreover, controlling the solar panels at key development stages of the crop is the central lever in the synergy of dynamic AV Systems. The methodology presented here applies not only to Wheat but to a wider range of crops and climate conditions, hence opening promising perspectives to optimize AV systems sizing and agronomic benefits

La cohésion des chromatides sœurs chez Escherichia coli

Chez les bactéries, la ségrégation du chromosome est initiée durant la phase de réplication. Des expériences de time lapse, utilisées pour observer que la dynamique des loci frères durant le cycle cellulaire, montrent que, chez Escherichia coli, les régions sœurs restent colocalisées pour une période significative dans les régions des macrodomaines du chromosome et pour une courte période dans les régions non-structurées. Nous nous sommes posés la question suivante: est ce que l étape de colocalisation révèle une réelle cohésion entre les chromatides sœurs ? Pour y répondre, nous avons développé un outil génétique, alternatif aux outils de biologie cellulaire, permettant de mesurer la distance entre les chromatides sœurs de manière directe. La fréquence de recombinaison intermoléculaire médiée par la recombinase Cre entre les sites loxP positionnés sur les chromatides sœurs est mesurée pour différentes positions. De cette fréquence, nous avons pu déduire la proximité entre les chromatides sœurs. Nous révélons que les loci frères restent proche l un de l autre pour une courte période après la réplication. Nous appelons cette étape la cohésion moléculaire, celle-ci est dépendante du locus considéré. Nous montrons que les facteurs qui favorisent la colocalisation des foci frères n augmentent pas nécessairement l habilité des loci frères à recombiner. En effet, la protéine MatP, un acteur de la colocalisation des macrodomaines Ter, n affecte pas la cohésion entre les deux copies de cette région. La Topoisomérase IV est un facteur essentiel à la ségrégation des chromosomes. En son absence, les chromosomes ne peuvent se ségréger et restent colocalisés dans la cellule. Nous révélons par le test de recombinaison que l absence de Topoisométase IV dans les cellules provoque une augmentation des interactions entre chromatides sœurs. Au final, nous avons montré que l étape de cohésion est différente de la colocalisation, que les mécanismes moléculaires diffèrent d une étape à l autre et que les liens de précaténation moduleraient la cohésion post-réplicative entre chromatides sœurs.In bacteria, the segregation of the chromosome is initiated during the replication phase. Time lapse experiments, used to watch the dynamic of loci during cell cycle, showed, in Escherichia coli, that the sister loci remain colocalized for a significant amount of time in the macrodomain regions of the chromosome and for shorter period in the Non Structured regions. We asked the following question: does this colocalization step reveal a real cohesion between the sister chromatids? To answer, we have developed a genetic tool, alternative to cell biology tools, to measure the distance between sister chromatids directly. The frequency of intermolecular recombination mediated by Cre recombinase loxP sites located on sister chromatids was measured for various loci. From this frequency we were able to deduce the proximity of sister chromatids. We revealed that sister loci remained in close proximity for a short period following replication. We called this step molecular cohesion, it is dependent on the considered locus. We showed that factors that promote colocalisation of sister foci do not necessarily increase the ability of sister loci to recombine. Indeed, the MatP protein, an actor of macrodomain Ter colocalisation, does not affect the cohesion between the two copies of this region. The TopoIV is essential for the segregation of chromosomes. In its absence, the chromosomes can not segregate and remain colocalized in the cell. We reveal by recombinaison assy that the absence of Topoisomerase IV revealed an increase of interactions between sister chromatids. To conclude, we have shown that the cohesion step is different from the colocalisation step, the molecular mechanisms differ from one stage to another and précaténation links take part in the post-replicative cohesion between sister chromatidsPARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Exergy assessment and sustainability of a simple off-shore oscillating water column device

This work was funded by Andalusian Regional Government, Spain, projects P18-RT-3595 and B-RNM-346-UGR18. Research to be continued under grant TED2021-131717B-I00 funded by MCIN/AEI/ 10.13039/501100011033 and, as appropriate, by ERDF A way of making Europe, by he European Union and by the European Union NextGenerationEU/PRTR.This paper present a research on the performance efficiency and sustainability of an Oscillating Water Column (OWC) simple off-shore device, accounting for the influence of governing thermodynamic variables (moisture, temperature, pressure) in the compression/expansion polytropic process. The work proposes a simple off-shore OWC experimental set up as the basis of the study. The analysis takes into consideration both gas subsystems inside and outside the OWC, to achieve a better understanding of the conservative nature of entropy system variable, the net exchange balance, the effects on efficiency and exergy destruction, and the interpretation of the OWC as a thermodynamic engine. Results show that, within the context of the set up, moderate wave climate conditions contribute to a better efficiency of the device in terms of output power, providing with a low impact on exergy destruction and high sustainability in terms of renewability index.Andalusian Regional Government, Spain, projects P18-RT-3595 and B-RNM-346-UGR18Grant TED2021-131717B-I00 funded by MCIN/AEI/ 10.13039/501100011033ERDF A way of making Europe, by he European Union and by the European Union NextGenerationEU/PRT

Microsatellite Markers Confirm Self‐Pollination and Autogamy in Wild Populations of Vanilla mexicana Mill. (syn. V. inodora) (Orchidaceae) in the Island of Guadeloupe

The study aimed at evaluating the mating system of Vanilla mexicana (Orchidaceae) in natural populations in the island of Guadeloupe. A total of 132 V. mexicana samples were collected from 12 sites in Guadeloupe (Basse‐Terre). Five other samples coming from Martinique and Mexico completed our analyses. Reproductive biology experiments excluding pollinators with bagged flowers revealed 53.9% fruit set, a value identical to the natural fruit set measured in the populations. These results suggested that V. mexicana, unlike most Vanilla species, was reproducing by self‐pollination and autogamy. Due to lack of specific DNA markers for V. mexicana, microsatellite markers, previously developed in other Vanilla species, were used for the genetic analyses. Only 6 out of the 33 markers tested were transferable and polymorphic in V. mexicana. A panel of 51 V. mexicana samples genotyped with 3 polymorphic loci was finally retained for Guadeloupe population genetic analyses. A heterozygote deficiency was detected, and the selfing rate was estimated to 74%. These results confirmed the reproductive biology results as self‐pollination and autogamy were the most likely explanation for this deficit. Results were compared to those from allogamous wild Vanilla species and discussed in the light of suggested existence of a pollinator for V. mexicana in other areas (Mexico)