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At least 55 records · Page 3Linked to original sources
PubMed1990

Differential staining of the cell cycle of plant cells using safranin and indigo-picrocarmine.

A trichrome staining technique using safranin-indigo-picrocarmine (SIPC) can be used to distinguish the various stages of the cell cycle in onion root tip. When the tissue was fixed first in formalin followed by picric acid and stained in SIPC, a clear differentiation of interphase nuclei into four color classes, viz., green, orange, red and brown can be recorded. Replacing crystal violet for safranin produces a similar pattern of differentiation of interphase nuclei into green, light blue, blue and deep blue. Autoradiographic study using 3H-thymidine as a DNA precursor demonstrates the reliability of the SIPC staining technique. All the orange and red nuclei are found to be labelled and therefore are in S phase of the cell cycle. Almost all the green nuclei are unlabelled and may be assigned to G1. The larger brown nuclei which are mostly unlabelled can be considered in G2 phase.

Autoradiography↗
PubMed2002

Type III-dependent translocation of the Xanthomonas AvrBs3 protein into the plant cell.

Many plant pathogenic bacteria utilize a conserved type III secretion system (TTSS) to deliver effector proteins into the host tissue. Indirect evidence has suggested that at least some effector proteins are translocated from the bacterial cytoplasm into the plant cell. Using an immunocytochemical approach, we demonstrate that the type III effector AvrBs3 from Xanthomonas campestris pv. vesicatoria localizes to nuclei of infected pepper leaves. Importantly, AvrBs3 translocation was observed in situ in native tissues of susceptible and resistant plants. AvrBs3 was detected in the nucleus as soon as 4 h post infection, which was dependent on a functional TTSS and the putative translocator HrpF. N-terminal AvrBs3 deletion derivatives are no longer secreted by the TTSS in vitro and could not be detected inside the host cells, suggesting that the N-terminus of AvrBs3 is important for secretion. Deletion of the nuclear localization signals in the AvrBs3 C-terminus, which are required for the AvrBs3-mediated induction of the hypersensitive reaction in resistant pepper plants, abolished AvrBs3 localization to the nucleus. This is the first report on direct evidence for translocation of a native type III effector protein from a plant pathogenic bacterium into the host cell.

Bacterial Proteins↗
PubMed2005

Modular cloning in plant cells.

New plant genes are being discovered at a rapid pace. Yet, in most cases, their precise function remains elusive. The recent advent of recombinational cloning techniques has significantly improved our ability to investigate gene functions systematically. For example, proteins fused with diverse fluorescent tags can be expressed at will using versatile cloning cassettes. In addition, novel binary T-DNA vectors are now available to assemble multiple DNA fragments simultaneously, which greatly facilitate plant cell and protein engineering.

Cloning, Molecular↗
PubMed2002

Characterization of two noncellulosomal subunits, ArfA and BgaA, from Clostridium cellulovorans that cooperate with the cellulosome in plant cell wall degradation.

Plant cell wall degradation by Clostridium cellulovorans requires the cooperative activity of its cellulases and hemicellulases. To characterize the alpha-L-arabinosidases that are involved in hemicellulose degradation, we screened the C. cellulovorans genomic library for clones with alpha-L-arabinofuranosidase or alpha-L-arabinopyranosidase activity, and two clones utilizing different substrates were isolated. The genes from the two clones, arfA and bgaA, encoded proteins of 493 and 659 amino acids with molecular weights of 55,731 and 76,414, respectively, and were located on neighboring loci. The amino acid sequences for ArfA and BgaA were related to alpha-L-arabinofuranosidase and beta-galactosidase, respectively, which are classified as family 51 and family 42 glycosyl hydrolases, respectively. Recombinant ArfA (rArfA) had high activity for p-nitrophenyl alpha-L-arabinofuranoside, arabinoxylan, and arabinan but not for p-nitrophenyl alpha-L-arabinopyranoside. On the other hand, recombinant BgaA (rBgaA) hydrolyzed not only p-nitrophenyl alpha-L-arabinopyranoside but also p-nitrophenyl beta-D-galactopyranoside. However, when the affinities of rBgaA for p-nitrophenyl alpha-L-arabinopyranoside and p-nitrophenyl beta-D-galactopyranoside were compared, the K(m) values were 1.51 and 6.06 mM, respectively, suggesting that BgaA possessed higher affinity for alpha-L-arabinopyranose residues than for beta-D-galactopyranoside residues and possessed a novel enzymatic property for a family 42 beta-galactosidase. Activity staining analyses revealed that ArfA and BgaA were located exclusively in the noncellulosomal fraction. When rArfA and rBgaA were incubated with beta-1,4-xylanase A (XynA), a cellulosomal enzyme from C. cellulovorans, on plant cell wall polymers, the plant cell wall-degrading activity was synergistically increased compared with that observed with XynA alone. These results indicate that, to obtain effective plant cell wall degradation, there is synergy between noncellulosomal and cellulosomal subunits.

Amino Acid Sequence↗
PubMed1997

The role of endoxyloglucan transferase in the organization of plant cell walls.

The plant cell wall plays a central role in morphogenesis as well as responsiveness to environmental signals. Xyloglucans are the principal component of the plant cell wall matrix and serve as cross-links between cellulose microfibrils to form the cellulose-xyloglucan framework. Endoxyloglucan transferase (EXGT), which was isolated and characterized in 1992, is an enzyme that mediates molecular grafting reaction between xyloglucan molecules. Structural studies on cDNAs encoding EXGT and its related proteins have disclosed the ubiquitous presence in the plant kingdom of a large multigene family of xyloglucan-related proteins (XRPs). Each XRP functions as either hydrolase or transferase acting on xyloglucans and is considered to be responsible for rearrangement of the cellulose-xyloglucan framework, the processes essential for the construction, modification, and degradation of plant cell walls. Different XRP genes exhibit potentially different expression profiles with respect to tissue specificity and responsiveness to hormonal and mechanical signals. The molecular approach to individual XRP genes will open a new path for exploring the controlling mechanisms by which the plant cell wall is constructed and reformed during plant growth and development.

Amino Acid Sequence↗
PubMed2002

Roles of the plasma membrane and the cell wall in the responses of plant cells to freezing.

In an effort to clarify the responses of a wide range of plant cells to freezing, we examined the responses to freezing of the cells of chilling-sensitive and chilling-resistant tropical and subtropical plants. Among the cells of the plants that we examined, those of African violet ( Saintpaulia grotei Engl.) leaves were most chilling-sensitive, those of hypocotyls in mungbean [ Vigna radiata (L.) R. Wilcz.] seedlings were moderately chilling-sensitive, and those of orchid [ Paphiopedilum insigne (Wallich ex Lindl.) Pfitz.] leaves were chilling-resistant, when all were chilled at -2 degrees C. By contrast, all these plant cells were freezing-sensitive and suffered extensive damage when they were frozen at -2 degrees C. Cryo-scanning electron microscopy (Cryo-SEM) confirmed that, upon chilling at -2 degrees C, both chilling-sensitive and chilling-resistant plant cells were supercooled. Upon freezing at -2 degrees C, by contrast, intracellular freezing occurred in Saintpaulia leaf cells, frost plasmolysis followed by intracellular freezing occurred in mungbean seedling cells, and extracellular freezing (cytorrhysis) occurred in orchid leaf cells. We postulate that chilling-related destabilization of membranes might result in the loss of the ability of the plasma membrane to act as a barrier against the propagation of extracellular ice in chilling-sensitive plant cells. We also examined the role of cell walls in the response to freezing using cells in which the plasma membrane had been disrupted by repeated freezing and thawing. In chilling-sensitive Saintpaulia and mungbean cells, the cells with a disrupted plasma membrane responded to freezing at -2 degrees C by intracellular freezing. By contrast, in chilling-resistant orchid cells, as well as in other cells of chilling-resistant and freezing-resistant plant tissues, including leaves of orchard grass ( Dactylis glomerata L.), leaves of Arabidopsis thaliana (L.) Heynh. and cortical tissues of mulberry ( Morus bombycis Koids.), cells with a disrupted plasma membrane responded to freezing by extracellular freezing. Our results indicate that, in the chilling-sensitive plants cells that we examined, not only the plasma membrane but also the cell wall lacked the ability to serve as a barrier against the propagation of extracellular ice, whereas in the chilling-resistant plant cells that we examined, not only the plasma membrane but also the cell wall acted as a barrier against the propagation of extracellular ice. It appears, therefore, that not only the plasma membrane but also the cell wall greatly influences the freezing behavior of plant cells.

Acclimatization↗
PubMed2000

Effects of hydrodynamic and interfacial forces on plant cell suspension systems.

Plant cells are perceived to be sensitive to the hydrodynamic environment in conventional bioreactors. Heightened sensitivity, relative to most bacterial cultures, is frequently attributed to larger plant cell sizes, extensive vacuolization and aggregation patterns. Early studies of shear sensitivity focused on cell lysis and/or loss of viability. More recently, an extensive array of sub-lethal responses has been identified. A fuller understanding of these sub-lytic effects may assist in the optimization of large-scale cultivation conditions. This paper reviews recent work on the hydrodynamic shear sensitivity of plant cell systems, under cultivation conditions and in purpose-built shearing devices. The relevance of different approaches to the characterization of the intensity of a given hydrodynamic environment is discussed. Indicators of cell response to hydrodynamic stress are evaluated. The potential significance of cellular defense mechanisms, observed in response to mechanical stimulants, is identified.

Bioreactors↗
PubMed1997

Plant cell morphogenesis: plasma membrane interactions with the cytoskeleton and cell wall.

Because plants are composed of immobile cells, plant morphogenesis requires mechanisms allowing precise control of cell expansion and cell division patterns. Cortical domains, localized in response to directional cues, are of central importance in establishing cell polarity, orienting cell division, and determining daughter cell fates in a wide variety of prokaryotic and eukaryotic organisms. Such domains consist of localized macromolecular complexes that, in plant cells, provide spatial control of cell expansion and cell division functions. The role of the cytoskeleton, plasma membrane, and targeted secretion to the cell wall in the spatial regulation of cell morphogenesis in plants is discussed in light of recent results from model organisms, including brown algal zygotes (e.g. Fucus). A general model, emphasizing the importance of cortical sites and targeted secretion, is proposed for morphogenesis in higher plant cells based on current knowledge and principles derived from analysis of the establishment of a stable cortical asymmetry in Fucus. The model illustrates mechanisms to direct the orientation of an asymmetric division resulting in daughter cells with different fates.

Animals↗
PubMed2001

Combining genetics and cell biology to crack the code of plant cell calcium signaling.

Plant hormones, light receptors, pathogens, and abiotic signals trigger elevations in the cytosolic calcium concentration, which mediate physiological and developmental responses. Recent studies are reviewed here that reveal how specific genetic mutations impair or modify stimulus-induced calcium elevations in plant cells. These studies provide genetic evidence for the importance of calcium as a second messenger in plant signal transduction. A fundamental question arises: How can different stimuli use the same second messenger, calcium, to mediate different responses? Recent research and models are reviewed that suggest that several important mechanisms contribute to specificity in calcium signaling in plant cells. These mechanisms include (i) activation of different calcium channels in the plasma membrane and organellar membranes, (ii) stimulus-specific calcium oscillation parameters, (iii) cell type-specific responses, and (iv) intracellular localization of calcium gradients and calcium elevations in plant cells.

Arabidopsis↗
PubMed1994

Large-scale insect and plant cell culture.

Currently, insect and plant cell cultures are not widely used to make products of commercial interest, largely because the development of large-scale cultivation methods is still in its infancy. With the advances made over the past year, some of the limitations associated with scale-up of these two types of expression system have been addressed. Increasing the oxygen supply and the concentration of various nutrients supplied to insect cells after infection has enabled high specific protein production to be maintained to higher cell densities than ever before, improving overall volumetric yields. Detailed work has focused on the capacity of insect cells to carry out complex post-translational modifications; however, as yet, evidence is conflicting as to the extent of protein processing and complex glycosylation possible in infected cells. In plant cell culture, the accepted axioms concerning large-scale culture have been re-examined. Recent studies have assessed culture at high cell densities and the constraints in reactor design resulting from the 'shear sensitivity' of plant cells. Results show that, as cell densities increase, alterations occur in the pathways of secondary metabolism, leading to decreases in specific productivity. The use of nutrient supplements and a medium cycling strategy shows promise for increasing and sustaining product formation. Furthermore, the importance of dissolved gas composition has been clearly demonstrated by use of a gas recirculation reactor. Reports of taxol and vindoline production in vitro demonstrate the potential and the necessity for further research in scale-up of plant cell culture.

Animals↗
PubMed1998

Sorting of proteins to vacuoles in plant cells.

An individual plant cell may contain at least two functionally and structurally distinct types of vacuoles: protein storage vacuoles and lytic vacuoles. Presumably a cell that stores proteins in vacuoles must maintain these separate compartments to prevent exposure of the storage proteins to an acidified environment with active hydrolytic enzymes where they would be degraded. Thus, the organization of the secretory pathway in plant cells, which includes the vacuoles, has a fascinating complexity not anticipated from the extensive genetic and biochemical studies of the secretory pathway in yeast. Plant cells must generate the membranes to form two separate types of tonoplast, maintain them as separate organelles, and direct soluble proteins from the secretory flow specifically to one or the other via separate vesicular pathways. Individual soluble and membrane proteins must be recognized and sorted into one or the other pathway by distinct, specific mechanisms. Here we review the emerging picture of how separate plant vacuoles are organized structurally and how proteins are recognized and sorted to each type.

Amino Acid Sequence↗
PubMed2000

Technological problems in cultivation of plant cells at high density. Reprinted from Biotechnology and Bioengineering, Vol. XXII, No. 6, Pages 1203-1218 (1981).

Using Cudrania tricuspidata cells as model plant cells which have high sensitivity to hydrodynamic stress, technological problems in the cultivation of the plant cells at high density were investigated. Using "shake" flasks on a reciprocal shaker and Erlenmeyer flasks on a rotary shaker and with a high supply of oxygen in order to obtain high cell densities in shaken cultures, particle breakdown and damage to the largest cell aggregate group (above 1981 microm in diameter) occurred and normal cell growth became impeded. The mass-transfer coefficient (K) for a model solid-liquid system (beta-naphthol particles and water) in place of a system of plant cells and a liquid medium was proposed as an intensity index of hydrodynamic stress effects on plant cells in suspension cultures under various conditions in the bioreactor systems. Normal cell growth was obtained under culture conditions for K values less than about 4.4 x 10(-3) cm/sec. The characteristics of various bioreactors used until now were investigated by considering the three main technological factors (capacity of oxygen supply, intensity of hydrodynamic stress effects on plant cells, and intensity of culture broth mixing and air-bubble dispersion). The most suitable bioreactor for culturing plant cells at high density was a jar fermentor with a modified paddle-type impeller (J-M). The yield of cell mass in the 10-liter J-M (working volume 5 liter) was about 30 g dry weight per liter of medium.

Bioreactors↗
PubMed1994

Mechanisms of the proliferation and differentiation of plant cells in cell culture systems.

Plant cell functions have been investigated in various cell culture systems. In this review, we summarize results obtained from investigations of gene expression during the cell cycle in synchronized cultures of Catharanthus roseus during somatic embryogenesis in suspension cultures of Daucus carota, during organogenesis in tissue cultures of Arabidopsis thaliana and during the transdifferentiation of isolated mesophyll cells to tracheary elements in single-cell cultures of Zinnia elegans.

Cell Cycle↗
PubMed2006

Tête à tête inside a plant cell: establishing compatibility between plants and biotrophic fungi and oomycetes.

'Compatibility' describes the complementary relationship between a plant species and an adapted pathogen species that underlies susceptibility and which ultimately results in disease. Owing to elaborate surveillance systems and defence mechanisms on the plant side and a common lack of adaptation of many microbial pathogens, resistance is the rule and compatibility the exception for most plant-microbe combinations. While there has been major scientific interest in 'resistance' in the past decade, which has revealed many of its underlying molecular components, the analysis of 'compatibility', although intimately intertwined with 'resistance', has not been pursued with a similar intensity. Various recent studies, however, provide a first glimpse of the pivotal players and potential molecular mechanisms essential for compatibility in both the plant and parasite partners. In this review we highlight these findings with a particular emphasis on obligate biotrophic and hemibiotrophic fungal and oomycete pathogens and discuss novel strategies that might help to uncover further the molecular principles underlying compatibility to these highly specialized pathogens.

Fungi↗