共查询到20条相似文献,搜索用时 0 毫秒
1.
Jessica Fitzgibbon Martina Beck Ji Zhou Christine Faulkner Silke Robatzek Karl Oparka 《The Plant cell》2013,25(1):57-70
Plasmodesmata (PD) form tubular connections that function as intercellular communication channels. They are essential for transporting nutrients and for coordinating development. During cytokinesis, simple PDs are inserted into the developing cell plate, while during wall extension, more complex (branched) forms of PD are laid down. We show that complex PDs are derived from existing simple PDs in a pattern that is accelerated when leaves undergo the sink–source transition. Complex PDs are inserted initially at the three-way junctions between epidermal cells but develop most rapidly in the anisocytic complexes around stomata. For a quantitative analysis of complex PD formation, we established a high-throughput imaging platform and constructed PDQUANT, a custom algorithm that detected cell boundaries and PD numbers in different wall faces. For anticlinal walls, the number of complex PDs increased with increasing cell size, while for periclinal walls, the number of PDs decreased. Complex PD insertion was accelerated by up to threefold in response to salicylic acid treatment and challenges with mannitol. In a single 30-min run, we could derive data for up to 11k PDs from 3k epidermal cells. This facile approach opens the door to a large-scale analysis of the endogenous and exogenous factors that influence PD formation. 相似文献
2.
The occurrence of plasmodesmata has been studied in the trichomesand leaf epidermis of 12 species of the Asclepiadaceae. Plasmodesmataare observed in the walls of hair cells, epidermal cells, andstomatal apparatus. Plasmodesmata are present between adjacenthair cells from base to the apex; epidermal and basal hair cells;epidermal cells; epidermal and subsidiary cells; subsidiarycells, and subsidiary and guard cells, thus establishing mutualsymplasmatic contacts. 相似文献
3.
4.
5.
6.
7.
Formation of Complexes at Plasmodesmata for Potyvirus Intercellular Movement Is Mediated by the Viral Protein P3N-PIPO 总被引:1,自引:0,他引:1
Taiyun Wei Changwei Zhang Jian Hong Ruyi Xiong Kristin D. Kasschau Xueping Zhou James C. Carrington Aiming Wang 《PLoS pathogens》2010,6(6)
Intercellular transport of viruses through cytoplasmic connections, termed plasmodesmata (PD), is essential for systemic infection in plants by viruses. Previous genetic and ultrastructural data revealed that the potyvirus cyclindrical inclusion (CI) protein is directly involved in cell-to-cell movement, likely through the formation of conical structures anchored to and extended through PD. In this study, we demonstrate that plasmodesmatal localization of CI in N. benthamiana leaf cells is modulated by the recently discovered potyviral protein, P3N-PIPO, in a CI:P3N-PIPO ratio-dependent manner. We show that P3N-PIPO is a PD-located protein that physically interacts with CI in planta. The early secretory pathway, rather than the actomyosin motility system, is required for the delivery of P3N-PIPO and CI to PD. Moreover, CI mutations that disrupt virus cell-to-cell movement compromise PD-localization capacity. These data suggest that the CI and P3N-PIPO complex coordinates the formation of PD-associated structures that facilitate the intercellular movement of potyviruses in infected plants. 相似文献
8.
A Common Position-Dependent Mechanism Controls
Cell-Type
Patterning and GLABRA2 Regulation in the
Root and Hypocotyl Epidermis of Arabidopsis 总被引:6,自引:1,他引:6 下载免费PDF全文
Chen-Yi Hung Yan Lin Meng Zhang Susan Pollock M. David Marks John Schiefelbein 《Plant physiology》1998,117(1):73-84
A position-dependent pattern of epidermal cell types is produced during root development in Arabidopsis thaliana. This pattern is reflected in the expression pattern of GLABRA2 (GL2), a homeobox gene that regulates cell differentiation in the root epidermis. GL2 promoter::GUS fusions were used to show that the TTG gene, a regulator of root epidermis development, is necessary for maximal GL2 activity but is not required for the pattern of GL2 expression. Furthermore, GL2-promoter activity is influenced by expression of the myc-like maize R gene (35S::R) in Arabidopsis but is not affected by gl2 mutations. A position-dependent pattern of cell differentiation and GL2-promoter activity was also discovered in the hypocotyl epidermis that was analogous to the pattern in the root. Non-GL2-expressing cell files in the hypocotyl epidermis located outside anticlinal cortical cell walls exhibit reduced cell length and form stomata. Like the root, the hypocotyl GL2 activity was shown to be influenced by ttg and 35S::R but not by gl2. The parallel pattern of cell differentiation in the root and hypocotyl indicates that TTG and GL2 participate in a common position-dependent mechanism to control cell-type patterning throughout the apical-basal axis of the Arabidopsis seedling. 相似文献
9.
10.
Protein phosphatase 2A (PP2A) consists of three types of subunits: a catalytic(C), a scaffolding (A), and a regulatory (B) subunit. In Arabidopsisthaliana and other organisms the regulatory Bsubunits are divided into at least three non-related groups, B55, B’ and B″.Flowering time in plants mutated in B55 or B''genes were investigated in this work. The PP2A-b55α andPP2A-b55β (knockout) lines showed earlier flowering thanWT, whereas a PP2A-b’γ (knockdown) line showed late flowering.Average advancements of flowering in PP2A-b55 mutants were 3.4days in continuous light, 6.6 days in 12 h days, and 8.2 days in 8 h days.Average delays in the PP2A-b’γ mutant line were 7.1 days in 16h days and 4.7 days in 8 h days. Expression of marker genes of geneticallydistinct flowering pathways (CO, FLC, MYB33, SPL3), and thefloral integrator (FT, SOC1) were tested in WT, pp2a mutants,and two known flowering time mutants elf6 andedm2. The results are compatible with B55 acting at and/ordownstream of the floral integrator, in a non-identified pathway. B’γ was involved in repression of FLC, the mainflowering repressor gene. For B’γ the results are consistentwith the subunit being a component in the major autonomous flowering pathway. Inconclusion PP2A is both a positive and negative regulator of flowering time,depending on the type of regulatory subunit involved. 相似文献
11.
James Sinnett-Smith Rodrigo Jacamo Robert Kui YunZu M. Wang Steven H. Young Osvaldo Rey Richard T. Waldron Enrique Rozengurt 《The Journal of biological chemistry》2009,284(20):13434-13445
Rapid protein kinase D (PKD) activation and phosphorylation via protein
kinase C (PKC) have been extensively documented in many cell types cells
stimulated by multiple stimuli. In contrast, little is known about the role
and mechanism(s) of a recently identified sustained phase of PKD activation in
response to G protein-coupled receptor agonists. To elucidate the role of
biphasic PKD activation, we used Swiss 3T3 cells because PKD expression in
these cells potently enhanced duration of ERK activation and DNA synthesis in
response to Gq-coupled receptor agonists. Cell treatment with the
preferential PKC inhibitors GF109203X or Gö6983 profoundly inhibited PKD
activation induced by bombesin stimulation for <15 min but did not prevent
PKD catalytic activation induced by bombesin stimulation for longer times
(>60 min). The existence of sequential PKC-dependent and PKC-independent
PKD activation was demonstrated in 3T3 cells stimulated with various
concentrations of bombesin (0.3–10 nm) or with vasopressin, a
different Gq-coupled receptor agonist. To gain insight into the
mechanisms involved, we determined the phosphorylation state of the activation
loop residues Ser744 and Ser748. Transphosphorylation
targeted Ser744, whereas autophosphorylation was the predominant
mechanism for Ser748 in cells stimulated with Gq-coupled
receptor agonists. We next determined which phase of PKD activation is
responsible for promoting enhanced ERK activation and DNA synthesis in
response to Gq-coupled receptor agonists. We show, for the first
time, that the PKC-independent phase of PKD activation mediates prolonged ERK
signaling and progression to DNA synthesis in response to bombesin or
vasopressin through a pathway that requires epidermal growth factor
receptor-tyrosine kinase activity. Thus, our results identify a novel
mechanism of Gq-coupled receptor-induced mitogenesis mediated by
sustained PKD activation through a PKC-independent pathway.The understanding of the mechanisms that control cell proliferation
requires the identification of the molecular pathways that govern the
transition of quiescent cells into the S phase of the cell cycle. In this
context the activation and phosphorylation of protein kinase D
(PKD),4 the founding
member of a new protein kinase family within the
Ca2+/calmodulin-dependent protein kinase (CAMK) group and separate
from the previously identified PKCs (for review, see Ref.
1), are attracting intense
attention. In unstimulated cells, PKD is in a state of low catalytic (kinase)
activity maintained by autoinhibition mediated by the N-terminal domain, a
region containing a repeat of cysteinerich zinc finger-like motifs and a
pleckstrin homology (PH) domain
(1–4).
Physiological activation of PKD within cells occurs via a
phosphorylation-dependent mechanism first identified in our laboratory
(5–7).
In response to cellular stimuli
(1), including phorbol esters,
growth factors (e.g. PDGF), and G protein-coupled receptor (GPCR)
agonists (6,
8–16)
that signal through Gq, G12, Gi, and Rho
(11,
15–19),
PKD is converted into a form with high catalytic activity, as shown by in
vitro kinase assays performed in the absence of lipid co-activators
(5,
20).During these studies multiple lines of evidence indicated that PKC activity
is necessary for rapid PKD activation within intact cells. For example, rapid
PKD activation was selectively and potently blocked by cell treatment with
preferential PKC inhibitors (e.g. GF109203X or Gö6983) that do
not directly inhibit PKD catalytic activity
(5,
20), implying that PKD
activation in intact cells is mediated directly or indirectly through PKCs.
Many reports demonstrated the operation of a rapid PKC/PKD signaling cascade
induced by multiple GPCR agonists and other receptor ligands in a range of
cell types (for review, see Ref.
1). Our previous studies
identified Ser744 and Ser748 in the PKD activation loop
(also referred as activation segment or T-loop) as phosphorylation sites
critical for PKC-mediated PKD activation
(1,
4,
7,
17,
21). Collectively, these
findings demonstrated the existence of a rapidly activated PKC-PKD protein
kinase cascade(s). In a recent study we found that the rapid PKC-dependent PKD
activation was followed by a late, PKC-independent phase of catalytic
activation and phosphorylation induced by stimulation of the bombesin
Gq-coupled receptor ectopically expressed in COS-7 cells
(22). This study raised the
possibility that PKD mediates rapid biological responses downstream of PKCs,
whereas, in striking contrast, PKD could mediate long term responses through
PKC-independent pathways. Despite its potential importance for defining the
role of PKC and PKD in signal transduction, this hypothesis has not been
tested in any cell type.Accumulating evidence demonstrates that PKD plays an important role in
several cellular processes and activities, including signal transduction
(14,
23–25),
chromatin organization (26),
Golgi function (27,
28), gene expression
(29–31),
immune regulation (26), and
cell survival, adhesion, motility, differentiation, DNA synthesis, and
proliferation (for review, see Ref.
1). In Swiss 3T3 fibroblasts, a
cell line used extensively as a model system to elucidate mechanisms of
mitogenic signaling
(32–34),
PKD expression potently enhances ERK activation, DNA synthesis, and cell
proliferation induced by Gq-coupled receptor agonists
(8,
14). Here, we used this model
system to elucidate the role and mechanism(s) of biphasic PKD activation.
First, we show that the Gq-coupled receptor agonists bombesin and
vasopressin, in contrast to phorbol esters, specifically induce PKD activation
through early PKC-dependent and late PKC-independent mechanisms in Swiss 3T3
cells. Subsequently, we demonstrate for the first time that the
PKC-independent phase of PKD activation is responsible for promoting ERK
signaling and progression to DNA synthesis through an epidermal growth factor
receptor (EGFR)-dependent pathway. Thus, our results identify a novel
mechanism of Gq-coupled receptor-induced mitogenesis mediated by
sustained PKD activation through a PKC-independent pathway. 相似文献
12.
The localization of pathogenesis-related (PR) proteins inducedin tobacco leaves by treatment with potassium salicylate ora hypersensitive response to tobacco mosaic virus (TMV) infectionwas studied using immunochemical methods. Total PR protein levelsincreased with time after these treatments. The proportion ofPR proteins in the intercellular spaces to the total contentin the leaf discs rapidly rose in the later stage of the treatmentto about 75% on the 9th day after salicylate treatment and tomore than 80% on the 6th to 9th day after TMV inoculation. After5 days of salicylate treatment, the amounts of PR proteins inthe peeled leaf epidermis were two fold those in the mesophylltissue. Only five percent or less of the total PR proteins inthe epidermal and mesophyll tissues of salicylate-treated leaveswere detected in the isolated epidermal and mesophyll protoplasts.The sugar content in highly purified PR la, lb and lc was lessthan one mole of monosaccharide per mole of each protein. Theseresults show that the PR proteins are non-glycoproteins secretedinto the intercellular spaces. (Received January 16, 1987; Accepted July 14, 1987) 相似文献
13.
Zhu Zhi-qing Chu Chih-ching Sun Jing-san Sun Ching-san Li Shou-quan Zhu Ying-min 《植物学报(英文版)》1984,26(2)
Light and electron microscopic observations show that a kind of spherical electron-dense body appears in the dediffercntiating mesophyll cells and their subdivided cells in tobacco leaf explants cultured for more than two days. The larger electron-dense bodies (1.0–1.5μm in diameter) present in vacuoles while the smaller ones (0.1–0.8 m in diameter) in cytoplasm. This implies that the bodies first can be formed in cytoplasm and then secreted into vacuoles. Since the bodies can be fixed with glutaradehyde and 3H- leucine can incorporated into them, they may be recognized as protein bodies. The protein bodies usually closly combined with newly formed cytoplasmic masses so we suggest that they probably play some role in cytoplasmic growth of dedifferentiafing ceils. 相似文献
14.
15.
16.
利用扫描电子显微镜对鼠李科(Rhamnaceae)14属41种4变种的叶表皮形态进行了观察。结果表明:鼠李科植物叶表皮纹饰为皱状或网状,表面近光滑、具条纹或鳞片状粗糙;除蛇藤(Colubrina asiatica)叶上表皮有少量气孔外,其余植物气孔只存在于下表皮,椭圆形、卵形或圆形,孔盖光滑或具波纹状、颗粒状、瘤状、鳞片状附属物;孔盖内缘光滑、浅波状或外卷。这些叶表皮微形态对于一些种及种下分类群的划分有一定的参考作用。 相似文献
17.
Plastid development involves the programmed accumulation of proteins. Most plastid proteins are synthesized in the cytosol and imported into the organelle by an envelope-based protein import apparatus. Previous studies have shown that developmental rates of protein accumulation correspond to mRNA levels. Here, we examined the relationship between plastid development and the activity of the protein import apparatus. Developing plastids, primarily from wheat leaves, were analyzed for their protein import capability in vitro. Import capability, initially high in proplastids, declined as much as 20-fold as plastid development approached either the mature etioplast or the mature chloroplast. The observed decline was not due to senescence, nonspecific inhibitors, or protein turnover. Furthermore, the import capability of mature etioplasts, initially very low, was transiently reactivated during light-mediated redifferentiation into chloroplasts. These results suggest that plant cells regulate the import apparatus in concert with the protein demands of the developing plastids. 相似文献
18.
Heterogeneity of Mitochondrial Protein Biogenesis during Primary
Leaf Development in Barley 总被引:4,自引:1,他引:4 下载免费PDF全文
The natural developmental gradient of light-grown primary leaves of barley (Hordeum vulgare L.) was used to analyze the biogenesis of mitochondrial proteins in relation to the age and physiological changes within the leaf. The data indicate that the protein composition of mitochondria changes markedly during leaf development. Three distinct patterns of protein development were noted: group A proteins, consisting of the E1 β-subunit of the pyruvate dehydrogenase complex, ORF156, ORF577, alternative oxidase, RPS12, cytochrome oxidase subunits II and III, malic enzyme, and the α- and β-subunits of F1-ATPase; group B proteins, consisting of the E1 α-subunit of the pyruvate dehydrogenase complex, isocitrate dehydrogenase, HSP70A, cpn60C, and cpn60B; and group C proteins, consisting of the four subunits of the glycine decarboxylase complex (P, H, T, and L proteins), fumarase, and formate dehydrogenase. All of the proteins increased in concentration from the basal meristem to the end of the elongation zone (20.0 mm from the leaf base), whereupon group A proteins decreased, group B proteins increased to a maximum at 50 mm from the leaf base, and group C proteins increased to a maximum at the leaf tip. This study provides evidence of a marked heterogeneity of mitochondrial protein composition, reflecting a changing function as leaf cells develop photosynthetic and photorespiratory capacity. 相似文献
19.
20.
Focal contacts are transmembrane links between the extracellular matrix and the actin cytoskeleton that play a critical role in directed cell migration, adhesion, and normal growth. Several different component proteins of the focal contact show develop-mentally dependent changes in expression, suggesting that this is an important mechanism by which focal contact formation is controlled during embryogenesis. In this report we examine the expression of focal contact-associated proteins in human fetal and neonatal melanocytes using Western blotting. We show that expression of paxillin, a 69-kDa vinculin binding protein, is fourfold higher in neonatal melanocytes than in fetal melanocytes. Further, we show that talin, a high molecular weight structural protein that links integrins to the actin cytoskeleton, is proteolytically cleaved in fetal, but not in neonatal melanocytes. Immunofluorescence microscopy of cells grown on fibronectin confirmed the presence of paxillin, talin, and vinculin at the ends of actin stress fibers at presumptive focal contacts in melanocytes. Adhesion experiments to extracellular matrix ligands revealed significant differences in adhesion of fetal and neonatal melanocytes to fibronectin. The developmentally specific changes in focal contact protein expression observed suggest that this may be an important mechanism by which focal contact assembly is controlled in human melanocytes during development. 相似文献