45 research outputs found
Mapping of tonoplast intrinsic proteins in maturing and germinating Arabidopsis seeds reveals dual localization of embryonic TIPs to the tonoplast and plasma membrane
No full textWe have mapped the expression of the tonoplast intrinsic protein (TIP) gene family members in Arabidopsis seeds by fluorescent protein tagging of their genomic sequences and confocal microscopy. Three isoforms (TIP1;1, TIP2;1, and TIP2;2) have distinct patterns of expression in maternal tissues (outer integument and placento-chalazal region). Two isoforms, TIP3;1 and the previously uncharacterized TIP3;2, are the only detectable TIPs in embryos during seed maturation and the early stages of seed germination. Throughout these developmental stages, both isoforms co-locate to the tonoplast of the protein storage vacuoles, but also appear to label the plasma membrane. Plasma membrane labeling is specific to TIP3;1 and TIP3;2, is independent of the position of the fluorescent protein tag, and appears to be specific to early seed maturation and early germination stages. We discuss these results in the context of the predicted distribution of aquaporins in Arabidopsis seeds
Tonoplast intrinsic proteins and vacuolar identity
No full textTIPs (tonoplast intrinsic proteins) have been traditionally used as markers for vacuolar identity in a variety of plant species and tissues. In the present article, we review recent attempts to compile a detailed map of TIP expression in Arabidopsis, in order to understand vacuolar identity and distribution in this model species. We discuss the general applicability of these findings. We also review the issue of the intracellular targeting of TIPs and propose key emerging questions relative to the cell biology of this protein family
Localisation et dynamique sub-cellulaire des aquaporines d'Arabidopsis thaliana
No full textLes aquaporines sont des canaux facilitant le passage de l'eau au travers des membranes biologiques. Chez les plantes, elles contribuent de façon majeure au transport de l'eau dans tous les organes. Le maintien de l'équilibre hydrique de la plante entière dépend ainsi, en grande partie, de la régulation des AQP. Chez Arabidopsis, nous nous sommes intéressés au contrôle de la dynamique et de la localisation sub-cellulaires des PIP (Plasma membrane Intrinsic Protein). Ce contrôle semble être un mécanisme original de modulation de la fonction de nutrition hydrique des organes, et en particulier de la racine. La première partie nous a permis de mettre en évidence une relation entre l'effet du traitement salin sur l'inhibition du transport d'eau dans la racine et l'internalisation des PIP de la membrane plasmique (MP) vers des endosomes. En effet, dans ses étapes précoces, le traitement salin provoque une endocytose accrue des membranes lipidiques qui s'accompagne de celle des PIP. Cette découverte a été rendue possible grâce à l'utilisation de la technique de Fluorescence Recovery After Photobleaching (FRAP) qui nous a permis de discriminer entre des fusions PIP-GFP présentes dans la MP de celles présentes dans les compartiments endosomiaux, malgré leur très grande proximité. Précisément, nous avons, dans un premier temps, confirmé que les aquaporines cyclent de manière constitutive via une voie d'endocytose dépendante de l'adaptateur AP-2 et de la clathrine et via une voie d'exocytose dépendante de GNOM. Dans les étapes précoces du traitement salin, le pool d'endosomes et peut-être le cyclage entre ce pool et la MP sont augmentés selon une voie indépendante d'AP-2, mais par contre dépendante d'une Phosphatidyl-inositol-3 kinase. Ces données nous suggèrent l'existence de deux populations d'endosomes cyclant avec des dynamiques différentes pourrait, en partie, expliquer l'inhibition du transport d'eau de la racine observée en traitement salin, mais nous proposons également un mécanisme concomitant d'inhibition de l'activité intrinsèque des PIP. Par des approches de mutagenèse dirigées et de fusions à la GFP, la seconde partie de ce travail a permis de mettre en évidence un motif di-acide DXE (Asp4Val5Glu6) impliqué dans l'export hors du RE et situé sur l'extrémité N-terminale de PIP2;1. La mutation de l'un et/ou l'autre de ses résidus acides conduit à une rétention de la PIP2;1 dans le RE. Nous avons également étudié le rôle sur l'export hors du RE de modification post-traductionelles (MPT) originales que sont la di- et la mono-méthylation portées, respectivement, par les résidus Lys3 et Glu6. La Lys3 et la di-méthylation qu'elle porte ne sont pas impliquées dans l'export hors du RE de PIP2;1 et la question du rôle de la méthylation du Glu6 reste en suspens. Nous avons également mis en évidence des interactions entre sites où des mutations d'un résidu conduisent à des changements de nature des MPT des résidus à proximité. Enfin, la sur-expression d'une PIP2;1-GFP mutée sur le motif di-acide et retenue dans le RE, perturbe l'adressage à la MP des PIP2 et des PIP1 endogènes. Ce résultat suggère des interactions entre ces deux sous-groupes dans leur adressage à la MP. Nos études montrent qu'il existe de nombreux moyens de réguler la localisation et la dynamique sub-cellulaires des PIP, dans une cellule végétale. Il nous semble la mise en place de différentes voies d'endocytoses en réponse à des stimuli de l'environnement est un mécanisme de régulation des aquaporines crucial à explorer
In vivo imaging of the tonoplast intrinsic protein family in Arabidopsis roots
No full textBackground: Tonoplast intrinsic proteins (TIPs) are widely used as markers for vacuolar
compartments in higher plants. Ten TIP isoforms are encoded by the Arabidopsis genome. For
several isoforms, the tissue and cell specific pattern of expression are not known.
Results: We generated fluorescent protein fusions to the genomic sequences of all members of
the Arabidopsis TIP family whose expression is predicted to occur in root tissues (TIP1;1 and 1;2;
TIP2;1, 2;2 and 2;3; TIP4;1) and expressed these fusions, both individually and in selected pairwise
combinations, in transgenic Arabidopsis. Analysis by confocal microscopy revealed that TIP
distribution varied between different cell layers within the root axis, with extensive co-expression
of some TIPs and more restricted expression patterns for other isoforms. TIP isoforms whose
expression overlapped appeared to localise to the tonoplast of the central vacuole, vacuolar bulbs
and smaller, uncharacterised structures.
Conclusion: We have produced a comprehensive atlas of TIP expression in Arabidopsis roots,
which reveals novel expression patterns for not previously studied TIPs
Localisation et dynamique subcellulaires des aquaporines d'Arabidopsis thaliana
No full textMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF
Bio-Based and Robust Polydopamine Coated Nanocellulose/Amyloid Composite Aerogel for Fast and Wide-Spectrum Water Purification
No full textWater contamination resulting from human activities leads to the deterioration of aquatic ecosystems. This restrains the access to fresh water, which is the leading cause of mortality worldwide. In this work, we developed a bio-based and water-resistant composite aerogel from renewable nanofibrils for water remediation application. The composite aerogel consists of two types of cross-linked nanofibrils. Poly(dopamine)-coated cellulose nanofibrils and amyloid protein nanofibrils are forming a double networked crosslinked via periodate oxidation. The resulting aerogel exhibits good mechanical strength and high pollutants adsorption capability. Removal of dyes (rhodamine blue, acriflavine, crystal violet, malachite green, acid fuchsin and methyl orange), organic traces (atrazine, bisphenol A, and ibuprofen) and heavy metal ions (Pb(II) and Cu(II)) from water was successfully demonstrated with the composite aerogel. More specifically, the bio-based aerogel demonstrated good adsorption efficiencies for crystal violet (93.1% in 30 min), bisphenol A (91.7% in 5 min) and Pb(II) ions (94.7% in 5 min), respectively. Furthermore, the adsorption–desorption performance of aerogel for Pb(II) ions demonstrates that the aerogel has a high reusability as maintains satisfactory removal performances. The results suggest that this type of robust and bio-based composite aerogel is a promising adsorbent to decontaminate water from a wide range of pollutants in a sustainable and efficient way
Biochemical Society Annual Symposium No. 77 Tonoplast intrinsic proteins and vacuolar identity
No full textAbstract TIPs (tonoplast intrinsic proteins) have been traditionally used as markers for vacuolar identity in a variety of plant species and tissues. In the present article, we review recent attempts to compile a detailed map of TIP expression in Arabidopsis, in order to understand vacuolar identity and distribution in this model species. We discuss the general applicability of these findings. We also review the issue of the intracellular targeting of TIPs and propose key emerging questions relative to the cell biology of this protein family
Mechanisms and Effects of Retention of Over-Expressed Aquaporin AtPIP2;1 in the Endoplasmic Reticulum
No full textInternational audiencePlasma membrane intrinsic proteins (PIPs) are aquaporins that mediate water transport across the plant plasma membrane (PM). The present work addresses, using Arabidopsis AtPIP2;1 as a model, the mechanisms and significance of trafficking of newly synthesized PIPs from the endoplasmic reticulum (ER) to the Golgi apparatus. A functional diacidic export motif (Asp4-Val5-Glu6) was identified in the N-terminal tail of AtPIP2;1, using expression in transgenic Arabidopsis of site-directed mutants tagged with the green fluorescent protein (GFP). Confocal fluorescence imaging and a novel fluorescence recovery after photobleaching application based on the distinct diffusion of PM and intracellular AtPIP2;1-GFP forms revealed a retention in the ER of diacidic mutated forms, but with quantitative differences. Thus, the individual role of the two acidic Asp4 and Glu6 residues was established. In addition, expression in transgenic Arabidopsis of ER-retained AtPIP2;1-GFP constructs reduced the root hydraulic conductivity. Co-expression of AtPIP2;1-GFP and AtPIP1;4-mCherry constructs suggested that ER-retained AtPIP2;1-GFP may interact with other PIPs to hamper their trafficking to the PM, thereby contributing to inhibition of root cell hydraulic conductivity
Ligno-Cellulosic Fibre Sized with Nucleating Agents Promoting Transcrystallinity in Isotactic Polypropylene Composites
No full textThe mechanical performance of composites made from isotactic polypropylene reinforced with natural fibres depends on the interface between fibre and matrix, as well as matrix crystallinity. Sizing the fibre surface with nucleating agents to promote transcrystallinity is a potential route to improve the mechanical properties. The sizing of thermo-mechanical pulp and regenerated cellulose (Tencel™) fibres with α- and β-nucleating agents, to improve tensile strength and impact strength respectively, was assessed in this study. Polarised microscopy, electron microscopy and differential scanning calorimetry (DSC) showed that transcrystallinity was achieved and that the bulk crystallinity of the matrix was affected during processing (compounding and injection moulding). However, despite substantial changes in crystal structure in the final composite, the sizing method used did not lead to significant changes regarding the overall composite mechanical performance
Processing and Properties of MDF Fibre-Reinforced Biopolyesters with Chain Extender Additives
No full textBiopolyesters are a way to improve natural fibre composite sustainability. This study explores, for the first time, the potential of using medium density fibreboard (MDF) fibres to reinforce four biobased and biodegradable polyester matrices to create a fully “green composite.” Added at 30 wt %, MDF fibres did not improve the strength of the injection moulded NFCs and this deficiency was investigated by measuring fibre length, viscosity, and molecular weight of the matrices. Compared to other lignocellulosic fibres, the use of MDF fibres led to a molecular weight reduction of biopolyesters during processing. This effect was particularly striking for PLA. The addition of a chain extender enhanced the molecular weight of PLA and improved its processability. The tensile strength increase was correlated to a reduction of fibre pull-out, enabling the MDF fibre to fulfil its expected reinforcement role within the biopolyester composite
