1,720,989 research outputs found
Espressione differenziale di alfa e beta tubulina come marker dello sviluppo in Vitis vinifera L.
No full textIl citoscheletro delle cellule vegetali è una combinazione di differenti proteine che, interagendo specificatamente tra loro, servono al mantenimento della posizione e della dinamica di varie strutture endocellulari. Questa rete proteica è necessaria alla stabilità strutturale del citoplasma, all’ancoraggio di proteine e altre macromolecole, partecipa all’assemblaggio del fuso mitotico durante la separazione dei cromosomi, mantiene un preciso ordine interno alla cellula e contribuisce alla sintesi e alla struttura della parete cellulare nelle piante (Nick, 2007). I microtubuli sono polimeri eterodimerici di proteine globulari (α- e β-tubulina); queste ultime si allineano testa-coda a formare protofilamenti di lunghezza variabile. Generalmente, 13 protofilamenti formano un cilindro con diametro di circa 25 nm, il microtubulo. La caratteristica dei microtubuli è di essere dinamici, essendo capaci di assemblarsi e disassemblarsi rapidamente in risposta a fattori molto diversi e capaci di determinare la lunghezza e la stabilità dei microtubuli stessi
Alpha and beta-tubulin isoforms accumulate differently during bud development in Vitis vinifera L.
No full textChanges in the accumulation of alfa- and beta-tubulin during bud development in Vitis vinifera L.
No full textMicrotubules play important roles duringgrowth and morphogenesis of plant cells. Multiple isoformsof - and -tubulin accumulate in higher plant cells andoriginate either by transcription of diVerent genes or bypost-translational modiWcations. The use of diVerenttubulin isoforms involves the binding of microtubules todiVerent associated proteins and therefore generates microtubuleswith diVerent organizations and functions. Tubulinisoforms are diVerentially expressed in vegetative andreproductive structures according to the developmental programof plants. In grapevine (Vitis vinifera L.), vegetativeand reproductive structures appear on the same stem, makingthis plant species an excellent model to study the accumulationof tubulin isoforms. Proteins were extracted fromgrapevine samples (buds, leaves, Xowers and tendrils)using an optimized extraction protocol, separated by twodimensionalelectrophoresis and analyzed by immunoblotwith anti-tubulin antibodies. We identiWed eight -tubulinand seven -tubulin isoforms with pI around 4.8–5 thatgroup into separate clusters. More acidic -tubulin isoformswere detected in buds, while more basic -isoforms wereprevalently found in tendrils and Xowers. Similarly, moreacidic -tubulin isoforms were used in the bud stage whilea basic -tubulin isoform was essentially used in leaves andtwo central -tubulin isoforms were characteristically usedin tendrils and Xowers. Acetylated -tubulin was notdetected in any sample while tyrosinated -tubulin wasessentially found in large latent buds and in bursting budsin association with a distinct subset of tubulin isoform
Cold stress affects cell wall deposition and growth pattern in tobacco pollen tubes
No full textCold is an abiotic stress seriously threatening crop productivity by decreasing biomass production. The pollen tube is a target of cold stress, but also a useful model to address questions on cell wall biosynthesis. We here provide (immuno)cytological data relative to the impact of cold on the pollen tube cell wall. We clearly show that the growth pattern is severely affected by the stress, since the typical pulsed-growth mechanism accompanied by the periodic deposition of pectin rings is absent/severely reduced. Additionally, pectins and cellulose accumulate in bulges provoked by the stress, while callose, which colocalizes with pectins in the periodic rings formed during pulsed growth, accumulates randomly in the stressed samples. The altered distribution of the cell wall components is accompanied by differences in the localization of glucan synthases: cellulose synthase shows a more diffuse localization, while callose synthase shows a more frequent cytoplasmic accumulation, thereby denoting a failure in plasma membrane insertion. The cell wall observations are complemented by the analysis of intracellular Ca2+, pH and reactive oxygen species (ROS): while in the case of pH no major differences are observed, a less focused Ca2+ and ROS gradients are present in the stressed samples. The standard oscillatory growth of pollen tubes is recovered by transient changes of turgor pressure induced by hypoosmotic media. Overall our data contribute to the understanding of the impact that cold stress has on the normal development of the pollen tube and unveil the cell wall-related aberrant features accompanying the observed alterations
Heat stress affects the cytoskeleton and the delivery of sucrose synthase in tobacco pollen tubes
Full text linkHeat stress changes isoform content and distribution of cytoskeletal subunits in pollen tubes affecting accumulation of secretory vesicles and distribution of sucrose synthase, an enzyme involved in cell wall synthesis. Plants are sessile organisms and are therefore exposed to damages caused by the predictable increase in temperature. We have analyzed the effects of temperatures on the development of pollen tubes by focusing on the cytoskeleton and related processes, such as vesicular transport and cell wall synthesis. First, we show that heat stress affects pollen germination and, to a lesser extent, pollen tube growth. Both, microtubules and actin filaments, are damaged by heat treatment and changes of actin and tubulin isoforms were observed in both cases. Damages to actin filaments mainly concern the actin array present in the subapex, a region critical for determining organelle and vesicle content in the pollen tube apex. In support of this, green fluorescent protein-labeled vesicles are arranged differently between heat-stressed and control samples. In addition, newly secreted cell wall material (labeled by propidium iodide) shows an altered distribution. Damage induced by heat stress also extends to proteins that bind actin and participate in cell wall synthesis, such as sucrose synthase. Ultimately, heat stress affects the cytoskeleton thereby causing alterations in the process of vesicular transport and cell wall deposition
Heat-shock protein 70 binds microtubules and interacts with kinesin in tobacco pollen tubes
No full textThe heat-shock proteins of 70 kD are a family of ubiquitously expressed proteins important for protein
folding. Heat-shock protein 70 assists other nascent proteins to achieve the spatial structure and ultimately
helps the cell to protect against stress factors, such as heat. These proteins are localized in different cellular
compartments and are associated with the cytoskeleton. We identified a heat-shock protein 70 isoform in
the pollen tube of tobacco that binds to microtubules in an ATP-dependent manner. The heat-shock
protein 70 was identified as part of the so-called ATP-MAP (ATP-dependent microtubule-associated
protein) fraction, which also includes the 90-kD kinesin, a mitochondria-associated motor protein. The
identity of heat-shock protein 70 was validated by immunological assays and mass spectrometry. Sequence
analysis showed that this heat-shock protein 70 is more similar to specific heat-shock proteins of
Arabidopsis than to corresponding proteins of tobacco. Two-dimensional electrophoresis indicated that this
heat-shock protein 70 isoform only is part of the ATP-MAP fraction and that is associated with the
mitochondria of pollen tubes. Sedimentation assays showed that the binding of heat-shock protein 70 to
microtubules is not affected by AMPPNP but it increases in the presence of the 90-kD kinesin. Binding of
heat-shock protein 70 to microtubules occurs only partially in the presence of ATP but it does not occur if,
in addition to ATP, the 90-kD kinesin is also present. Data suggest that the binding (but not the release) of
heat-shock protein 70 to microtubules is facilitated by the 90-kD kinesin
Depletion of sucrose induces changes in the tip growth mechanism of tobacco pollen tubes
No full textBackground and Aims
Pollen tubes are rapidly growing, photosynthetically inactive cells that need high rates of energy to support growth. Energy can derive from internal and external storage sources. The lack of carbon sources can cause various problems during pollen tube growth, which in turn could affect the reproduction of plants.
Methods
We analysed the effects of energy deficiency on the development of Nicotiana tabacum pollen tubes by replacing sucrose with glycerol in the growth medium. We focused on cell growth and related processes, such as metabolite composition and cell wall synthesis.
Key Results
We found that the lack of sucrose affects pollen germination and pollen tube length during a specific growth period. Both sugar metabolism and ATP concentration were affected by sucrose shortage when pollen tubes were grown in glycerol-based media; this was related to decreases in the concentrations of glucose, fructose and UDP-glucose. The intracellular pH and ROS levels also showed a different distribution in pollen tubes grown in sucrose-depleted media. Changes were also observed at the cell wall level, particularly in the content and distribution of two enzymes related to cell wall synthesis (sucrose synthase and callose synthase). Furthermore, both callose and newly secreted cell wall material (mainly pectins) showed an altered distribution corresponding to the lack of oscillatory growth in pollen tubes. Growth in glycerol-based media also temporarily affected the movement of generative cells and, in parallel, the deposition of callose plugs.
Conclusion
Pollen tubes represent an ideal model system for studying metabolic pathways during the growth of plant cells. In our study, we found evidence that glycerol, a less energetic source for cell growth than sucrose, causes critical changes in cell wall deposition. The evidence that different aspects of pollen tube growth are affected is an indication that pollen tubes adapt to metabolic stress
How nitrogen changes protein expression in Cladonia portentosa: the effect of form, dose, time of exposure, and PK addition
No full textThe cytoskeleton of pollen tubes and how it determines the physico-mechanical properties of cell wall
No full textThe growth of pollen tubes is a complex process that requires the synchronized activity of many different factors. Pollen tubes grow by penetrating through relatively solid tissues of the pistil. In doing so, pollen tubes need a specialized shape consisting of a tubular axis culminating with a hemispherical dome. In order to maintain such a shape, pollen tubes must build a dynamic cell wall which is highly adapted to the cell’s penetrating activity. Therefore, the molecular mechanism controlling the pollen tube architecture is critical. In growing pollen tubes, the cytoskeleton controls the intracellular transport of organelles and vesicles. Movement of membrane-bounded structures is necessary for the apex-constrained growth of pollen tubes and for proper assembly of the cell wall. This process is strictly related to the fine-tuned deposition of specific proteins and polysaccharides, which contribute to local differentiation of cell wall texture and thus to the growth pattern of pollen tubes. This chapter will focus on the molecular relationships between cytoskeleton and cell wall deposition in pollen tubes in order to highlight how the cytoskeleton controls the shaping of pollen tubes
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