Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “vascular bundle”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed2005

AtGLR3.4, a glutamate receptor channel-like gene is sensitive to touch and cold.

The Arabidopsis genome encodes for 20 members of putative ligand-gated channels, termed glutamate receptors (GLR). Despite the fact that initial studies suggested a role for GLRs in various aspects of photomorphogenesis, calcium homeostasis or aluminium toxicity, their functional properties and physiological role in plants remain elusive. Here, we have focussed on AtGLR3.4, which is ubiquitously expressed in Arabidopsis including roots, vascular bundles, mesophyll cells and guard cells. AtGLR3.4 encodes a glutamate-, touch-, and cold-sensitive member of this gene family. Abiotic stress stimuli such as touch, osmotic stress or cold stimulated AtGLR3.4 expression in an abscisic acid-independent, but calcium-dependent manner. In plants expressing the Ca(2+) -reporter apoaequorin, glutamate as well as cold elicited cytosolic calcium elevations. Upon glutamate treatment of mesophyll cells, the plasma membrane depolarised by about 120 mV. Both glutamate responses were transient in nature, sensitive to glutamate receptor antagonists, and were subject to desensitisation. One hour after eliciting the first calcium signal, a 50% recovery from desensitisation was observed, reflecting the stimulus-induced fast activation of AtGLR3.4 transcription. We thus conclude that AtGLR3.4 in particular and GLRs in general could play an important role in the Ca(2+) -based, fast transmission of environmental stress.

Arabidopsis↗
PubMed2006

Brittle stalk 2 encodes a putative glycosylphosphatidylinositol-anchored protein that affects mechanical strength of maize tissues by altering the composition and structure of secondary cell walls.

A spontaneous maize mutant, brittle stalk-2 (bk2-ref), exhibits dramatically reduced tissue mechanical strength. Reduction in mechanical strength in the stalk tissue was highly correlated with a reduction in the amount of cellulose and an uneven deposition of secondary cell wall material in the subepidermal and perivascular sclerenchyma fibers. Cell wall accounted for two-thirds of the observed reduction in dry matter content per unit length of the mutant stalk in comparison to the wildtype stalk. Although the cell wall composition was significantly altered in the mutant in comparison to the wildtype stalks, no compensation by lignin and cell wall matrix for reduced cellulose amount was observed. We demonstrate that Bk2 encodes a Cobra-like protein that is homologous to the rice Bc1 protein. In the bk2-ref gene, a 1 kb transposon-like element is inserted in the beginning of the second exon, disrupting the open reading frame. The Bk2 gene was expressed in the stalk, husk, root, and leaf tissues, but not in the embryo, endosperm, pollen, silk, or other tissues with comparatively few or no secondary cell wall containing cells. The highest expression was in the isolated vascular bundles. In agreement with its role in secondary wall formation, the expression pattern of the Bk2 gene was very similar to that of the ZmCesA10, ZmCesA11, and ZmCesA12 genes, which are known to be involved in secondary wall formation. We have isolated an independent Mutator-tagged allele of bk2, referred to as bk2-Mu7, the phenotype of which is similar to that of the spontaneous mutant. Our results demonstrate that mutations in the Bk2 gene affect stalk strength in maize by interfering with the deposition of cellulose in the secondary cell wall in fiber cells.

Biomechanical Phenomena↗
PubMed2007

The Triticum aestivum non-specific lipid transfer protein (TaLtp) gene family: comparative promoter activity of six TaLtp genes in transgenic rice.

Plant non-specific lipid transfer proteins (nsLTPs) are encoded by a multigene family and support physiological functions, which remain unclear. We adapted an efficient ligation-mediated polymerase chain reaction (LM-PCR) procedure that enabled isolation of 22 novel Triticum aestivum nsLtp (TaLtp) genes encoding types 1 and 2 nsLTPs. A phylogenetic tree clustered the wheat nsLTPs into ten subfamilies comprising 1-7 members. We also studied the activity of four type 1 and two type 2 TaLtp gene promoters in transgenic rice using the 1-Glucuronidase reporter gene. The activities of the six promoters displayed both overlapping and distinct features in rice. In vegetative organs, these promoters were active in leaves and root vascular tissues while no beta-Glucuronidase (GUS) activity was detected in stems. In flowers, the GUS activity driven by the TaLtp7.2a, TaLtp9.1a, TaLtp9.2d, and TaLtp9.3e gene promoters was associated with vascular tissues in glumes and in the extremities of anther filaments whereas only the TaLtp9.4a gene promoter was active in anther epidermal cells. In developing grains, GUS activity and GUS immunolocalization data evidenced complex patterns of activity of the TaLtp7.1a, TaLtp9.2d, and TaLtp9.4a gene promoters in embryo scutellum and in the grain epicarp cell layer. In contrast, GUS activity driven by TaLtp7.2a, TaLtp9.1a, and TaLtp9.3e promoters was restricted to the vascular bundle of the embryo scutellum. This diversity of TaLtp gene promoter activity supports the hypothesis that the encoded TaLTPs possess distinct functions in planta.

Amino Acid Sequence↗
PubMed2001

Phloem-specific expression of the pumpkin fruit trypsin inhibitor.

Vascular exudates of Cucurbita maxima (Duch.) contain a group of highly conserved serine proteinase inhibitors collectively called Pumpkin Fruit Trypsin Inhibitors (PFTIs) that prevent proteolytic activity of trypsin or chymotrypsin. Polyclonal antibodies raised against PFTIs were used to immunolocalize these low-molecular-weight proteins within the phloem tissue and to study their developmental expression. The inhibitors were translocated throughout the transport phloem and were present in vascular exudates collected from both source and sink tissues throughout the plant. During the early stages of vascular development, PFTIs accumulated specifically in sieve element-companion cell complexes of the phloem tissue. Transcripts were initially detected by reverse transcription-polymerase chain reaction in seedlings 1 d after germination and the protein detected 24 h later. Pumpkin fruit trypsin inhibitors were present in both cell types of differentiating and translocating sieve element-companion cell complexes. The inhibitors were detected in the phloem of the bicollateral vascular bundles, but the protein was most consistently localized within the cortical and bundle-associated extrafascicular phloem.

Base Sequence↗
PubMed1998

Three-dimensional analysis of the senescence program in rice (Oryza sativa L.) coleoptiles. Investigations of tissues and cells by fluorescence microscopy.

The coleoptile of rice (Oryza sativa L. cv. Nippon-bare) emerges from an imbibed seed on day 2 after sowing. Then, it matures and senesces rapidly. For analysis of the senescence pattern within individual coleoptiles, we monitored the distribution of chlorophyll (Chl) in entire coleoptiles and in cross-sections of coleoptiles by recording the autofluorescence of Chl. Degradation of Chl was apparent at the tip of the margins of opened-out coleoptiles on day 4, when the overall levels of soluble protein and Chl per coleoptile had reached maximum values. Then, senescence proceeded from the tip to the base and from the inner mesophyll cells towards the outer epidermis, excluding tissues along vascular bundles. Further analysis of cellular senescence using samples embedded in Technovit 7100 resin revealed that the senescence of each green mesophyll cell followed an identical program, which consisted of the following steps: (i) degradation of chloroplast DNA; (ii) condensation of the nucleus, decrease in the size of chloroplasts, degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase and chloroplast inner membranes; (iii) disorganization of the nucleus; (iv) complete loss of cellular components, distortion of the cell wall. Although the timing of each step and the rate at which each step was completed differed among cells of different locations within the coleoptile, this sequence was observed in all mesophyll cells in the coleoptile.

Cotyledon↗
PubMed1998

Isolation and molecular characterization of a new vegetative MADS-box gene from Solanum tuberosum L.

A cDNA clone, STMADS11, encoding a new MADS-box protein was isolated from Solanum tuberosum L. (potato). Expression of STMADS11 was found in all vegetative organs of the plant, but not in floral tissues. The expression was also detected in all developmental stages, from tuber sprouts to mature plants, reaching a maximum in well-developed organs. However, the level of STMADS11 mRNA was low in tissues such as resting tuber or sprouts developed in the cold, where the metabolic activity is reduced. "In situ" hybridizations performed on leaf and stem sections showed that the STMADS11 transcript is mainly associated with vascular bundles. Cladistic analysis arising from amino acid sequence comparison revealed that STMADS11 shows the highest similarity to STMADS16, another vegetative MADS-box gene from potato, and to the previously reported "orphan" genes AGL15 and AGL17 from Arabidopsis thaliana. Possible implications of these data in relation to STMADS11 function are discussed.

Amino Acid Sequence↗
PubMed1999

Chalcone reductase-homologous transcripts accumulate during development of stem-borne nodules on the tropical legume Sesbania rostrata.

During a search for genes with induced or enhanced expression in the early stages of development of stem-borne nodules on Sesbania rostrata, a cDNA with homology to chalcone reductase (CHR) genes was isolated. Here, we describe the characterization of a full-length CHR cDNA (Srchr1) and the pattern of CHR transcript accumulation in stem-borne nodules. Expression was correlated with both nodule development and bacterial invasion. In young nodules, CHR transcripts were observed in cells of the parenchyma, in cells around the nodule vascular bundles, and in the uninfected cells of the central tissue.

Alcohol Oxidoreductases↗
PubMed2006

Characterization of LEAFY COTYLEDON1-LIKE gene in Helianthus annuus and its relationship with zygotic and somatic embryogenesis.

The Helianthus annuus LEAFY COTYLEDON1-LIKE (HaL1L) gene encodes a heme-activated protein 3 subunit of the CCAAT box-binding factor. The phylogenetic analysis indicates that HaL1L is closely related to LEAFY COTYLEDON1 (LEC1)-type of Arabidopsis thaliana. In particular, the peptide results homologous to the LEC1-LIKE gene of A. thaliana, with which it shares a high amino acid sequence identity (56%). HaL1L transcripts are accumulated primarily at an early stage of sunflower embryogenesis. High levels of HaL1L messenger RNA (mRNA) have been detected in the developing embryo proper, suspensor, endosperm, integument, and integumentary tapetum cells, while in unfertilized ovules, HaL1L mRNA was present at rather low levels. In an attempt to examine the involvement of HaL1L on somatic embryogenesis, a somaclonal variant of H. annuus x H. tuberosus (EMB-2) that produces ectopic embryo- and shoot-like structures, arranged in clusters along leaf veins, was used. We found that the epiphyllous proliferation of ectopic embryos on EMB-2 leaves was associated to HaL1L mRNA accumulation. The detection of HaL1L transcripts was evident in somatic embryos at the heart- and early cotyledon-stage. On the contrary, no signal related to HaL1L transcript accumulation was observed in EMB-2 leaves characterized by the presence of shoot-like structures. Together, these results support the conclusion that the transcription of the HaL1L gene is maintained both in zygotic and in somatic embryogenesis. In addition, the ectopic accumulation of HaL1L mRNA in parenchymal cells around the vascular bundles of epiphyllous leaves opens the possibility that HaL1L could also be involved in switching somatic cell fate towards embryogenic competence.

Amino Acid Motifs↗
PubMed2007

Molecular characterization the YABBY gene family in Oryza sativa and expression analysis of OsYABBY1.

Members of the YABBY gene family have a general role that promotes abaxial cell fate in a model eudicot, Arabidopsis thaliana. To understand the function of YABBY genes in monocots, we have isolated all YABBY genes in Oryza sativa (rice), and revealed the spatial and temporal expression pattern of one of these genes, OsYABBY1. In rice, eight YABBY genes constitute a small gene family and are classified into four groups according to sequence similarity, exon-intron structure, and organ-specific expression patterns. OsYABBY1 shows unique spatial expression patterns that have not previously been reported for other YABBY genes, so far. OsYABBY1 is expressed in putative precursor cells of both the mestome sheath in the large vascular bundle and the abaxial sclerenchyma in the leaves. In the flower, OsYABBY1 is specifically expressed in the palea and lemma from their inception, and is confined to several cell layers of these organs in the later developmental stages. The OsYABBY1-expressing domains are closely associated with cells that subsequently differentiate into sclerenchymatous cells. These findings suggest that the function of OsYABBY1 is involved in regulating the differentiation of a few specific cell types and is unrelated to polar regulation of lateral organ development.

Amino Acid Sequence↗
PubMed1999

The Arabidopsis transposon Tag1 is active in rice, undergoing germinal transposition and restricted, late somatic excision.

Tag1 is an autonomous transposable element of Arabidopsis thaliana that displays tight developmental control of its excision during shoot development. To determine how Tag1 behaves in a monocotyledonous species, Tag1 was inserted in a 35S-GUS marker gene and the construct was introduced into rice. Tag1 showed somatic excision activity in four out of eleven transgenic lines examined. In leaves, excision was primarily restricted to vascular bundles and produced sectors composed of only a few cells. Excision events in flowers occurred predominantly in or near the major veins of the palea and lemma to produce small sectors. In roots, small sectors were evident, but they were few in number. These data show that the timing of Tag1 excision during rice shoot development is late and mimics the late excision behavior of Tag1 in Arabidopsis. One of the transgenic rice lines, which had a high frequency of somatic excision, produced several germinal revertants, one of which was characterized by a new Tag1 insertion band. The pattern of Tag1 transcripts and the footprint sequences left behind after excision in rice were found to be very similar to those in Arabidopsis. These results show that key properties of Tag1 transposition and behavior are conserved between monocots and dicots and that Tag1 has the potential to serve as an insertional mutagen in rice.

Arabidopsis↗
PubMed2003

Implications of interveinal distance for quantum yield in C4 grasses: a modeling and meta-analysis.

The distance between veins has the potential to affect photosynthesis in C(4) grasses because photon capture and photosynthetic carbon reduction are primarily restricted to vascular bundle sheath cells (BSC). For example, BSC density should increase as interveinal distance (IVD) decreases, and thus IVD may influence photon capture and photosynthesis in C(4) grasses. The objective of this study is to evaluate the potential importance of IVD to the function of C(4) grasses, and a literature survey is conducted to test the hypothesis that quantum yield of photosynthesis (Phi) increases with decreasing IVD. First, a meta-analysis of Phi and IVD values obtained for 12 C(4) grass species supports this hypothesis as Phi and IVD are significantly negatively correlated (r=-0.61). Second, a regression of carbon isotope discrimination (delta) versus IVD was conducted and the regression equation was used in a simple biochemical model that relates Phi to Delta and leakage of CO(2) from the BSC. The modeling analysis also supports the hypothesis that Phi decreases with increasing IVD in C(4) grasses. C(4) grasses are virtually absent from shaded habitats, and the biochemical model is employed to examine the implications of IVD for shade-tolerance in C(4) grasses. The model predicts that only those species with uncommonly small IVD values are able to tolerate prolonged shade.

Adaptation, Physiological↗
PubMed2005

Laticifers in Camptotheca acuminata Decne: distribution and structure.

In this paper, a system of laticifers in Camptotheca acuminata Decne (Nyssaceae) is described. Laticifers were already present in the leaf primordia of the shoot apex. In the mature leaves, laticifers were found in the midrib and in the larger veins, both in the parenchymatic region delimited by vascular bundles and in the cortex just external to the phloem. In the stem, laticifers were present in both the primary and secondary body, running parallel to the longitudinal axis. They were located in the pith and in the cortex proximal to the phloem. No laticifers were found in the roots. The histochemical analyses indicated that the main compounds accumulated in laticifers were phenols. Neutral lipids and fatty acids were also present. Ultrastructural observations showed osmiophilic globules both in the vacuoles and in the peripheral regions of the cytoplasm of the laticifer cells. Plastids were present, although altered, with some parallel membranes and lacking starch grains. The discovery in C. acuminata of a laticifer system, which had never been described for the order Cornales, could be of taxonomic value, also considering that this order has traditionally represented one of the most problematic groups of flowering plants.

Camptotheca↗
PubMed2006

Microautoradiographic localisation of [3H]sucrose and [3H]mannitol in Robinia pseudoacacia pulvinar tissues during phytochrome-mediated nyctinastic closure.

We have analysed the incorporation of [(3)H]sucrose and [(3)H]mannitol in pulvinar motor cells of Robinia pseudoacacia L. during phytochrome-mediated nyctinastic closure. Pairs of leaflets, excised 2 h after the beginning of the photoperiod, were fed with 50 mM [(3)H]sucrose or [(3)H]mannitol, irradiated with red (15 min) or far-red (5 min) light and placed in the dark for 2-3 h. Label uptake was measured in whole pulvini by liquid scintillation counting. The distribution of labelling in pulvinar sections was assessed by both light and electron microautoradiography. [(3)H]Sucrose uptake was twice that of [(3)H]mannitol incorporation in both red- and far-red-irradiated pulvini. In the autoradiographs, [(3)H]sucrose and [(3)H]mannitol labelling was localised in the area from the vascular bundle to the epidermis, mainly in vacuoles, cytoplasm, and cell walls. Extensor and flexor protoplasts displayed a different distribution of [(3)H]sucrose after red and far-red irradiation. Far-red light drastically reduced the [(3)H]sucrose incorporation in extensor protoplasts and caused a slight increase in internal flexor protoplasts. After red light treatment, no differences in [(3)H]sucrose labelling were found between extensor and flexor protoplasts. Our results indicate a phytochrome control of sucrose distribution in cortical motor cells and seem to rule out the possibility of sucrose acting as an osmoticum.

Autoradiography↗
PubMed2002

Ovules and seeds in Euphorbioideae (Euphorbiaceae): structure and systematic implications.

Ovule and seed structure in Euphorbioideae, one of the five euphorbiaceous subfamilies, is surveyed to evaluate its systematic implications on the basis of 79 species representing four of five tribes. All Euphorbioideae, like two other "uniovulate" subfamilies Acalyphoideae and Crotonoideae, but unlike most of two "biovulate" subfamilies Oldfieldioideae and Phyllanthoideae, consistently have a persistent and palisadal exotegmen composed of radially elongate, sclerotic, and pitted cells. Within Euphorbioideae, the tribe Stomatocalyceae (also with the palisadal exotegmen) is unusual in having vascular bundles in outer integument and clearly distinct from the remaining Euphorbioideae and the other "uniovulate" subfamilies. With the exclusion of Stomatocalyceae, Euphorbioideae are not anatomically divided into major groups such as a pseudanthial and a non-pseudanthial clade, but instead have some remarkable diversity within a tribe, a subtribe, and even a genus in the three ovule and seed characters: (1) the thickness of the inner integument, (2) the thickness of the outer integument, and (3) the presence or absence of an aril. Groups of genera and species wrapped by different combinations of their characteristics, however, are not necessarily harmonized with tribal or subtribal classifications available. Anatomical similarities and dissimilarities presented in this paper, as well as relationships among taxa presented in the classifications available, will be critically evaluated in the light of results of ongoing molecular phylogenetic analyses.

Journal Article↗
PubMed2002

Time-course of programmed cell death during leaf senescence in Eucommia ulmoides.

Leaves of Eucommia ulmoidesOliv. harvested between April to November were examined for programmed cell death (PCD) during growth and senescence. Leaves developed in April, becoming fully expanded in late May, remaining unchanged until November when they started to dehisce. Falling leaves retained a green color. Our results showed that (1) mesophyll cells gradually reduced their nuclei from September to November, (2) positive TUNEL signals appeared on the nuclei from August, (3) ladder-like DNA fragmentation occurred in September and October, and (4) a 20-kDa Ca(2+)-dependent DNase appeared in these same months. In fallen leaves, intact mesophyll cell nuclei could not be detected, but a few cells around the vascular bundle had nuclei. Therefore, (1) programmed cell death (PCD) of leaf cells occurred in the leaves of E. ulmoides, (2) the progress of mesophyll cell PCD lasted for more than 2 months, and (3) PCD of leaf cells was asynchronous in natural senescing leaves.

Apoptosis↗
PubMed2004

Histological analysis in shoot organogenesis from hypocotyl explants of Kandelia candel (Rhizophoraceae).

In vitro culture of hypocotyl explants from Kandelia candel, a common mangrove species, on hormone-free Murashige and Skoog (MS) medium resulted in shoot formation. Since the hypocotyls showed good potential for in vitro shoot multiplication, the process of bud primordium formation was analyzed from a histological viewpoint. A wound periderm first appeared at the top, exposed cut surface of the explants. The wound-induced meristem continued to divide giving rise to suberized cells oriented towards the cut surface. After formation of the suberized cell layers, the meristem and its inner derivatives differentiated into multilayered, uniformly packed parenchyma cells. Bud primordia differentiated from the dense cytoplasmic cells of the wound-induced meristem just beneath the suberized layer near the severed vascular bundles. Each explant produced several visible shoot buds. Furthermore, histological sections revealed that additional bud primordia were present within the explant just underneath the suberized cells and that these bud primordia appeared to be arrested in their development. The fact that additional bud primordia were present within the explant suggests that further manipulation of the explant is helpful to maximize the potential of this system.

Hypocotyl↗
PubMed2006

Anatomical injury induced by the eriophyid mite Aceria anthocoptes on the leaves of Cirsium arvense.

Anatomical injury of the leaves of the invasive species, Cirsium arvense (L.) Scop., caused by the eriophyid mite Aceria anthocoptes (Nal.), which is the only eriophyid mite that has been recorded on C. arvense worldwide, is described. The injury induced by the mite feeding on the leaves of C. arvense results in visible russeting and bronzing of the leaves. Other conspicuous deformations are folding and distortion of the leaf blade and curling of leaf edge, as well as gradual drying of leaves. The anatomical injury of the mature leaves of field-collected plants was limited to the epidermis of the lower leaf surface. However, on young leaves of experimentally infested plants, rust mite injuries extend to epidermal cells on both leaf surfaces and to those of deeper mesophyll layers. On these leaves, lesions on the lower leaf surface even affected the phloem of the vascular bundles. Leaf damage induced by A. anthocoptes is discussed with regard to the mite's potential as a biological control agent of C. arvense.

Animals↗
PubMed2004

CAZFP1, Cys2/His2-type zinc-finger transcription factor gene functions as a pathogen-induced early-defense gene in Capsicum annuum.

A pepper zinc-finger protein gene, CAZFP1 , encoding the Cys2/His2-type zinc-finger transcription factor was isolated from pepper leaves inoculated with an avirulent strain Bv5-4a of Xanthomonas campestris pv. vesicatoria . The CAZFP1 protein is a nuclear targeting protein, which functions as a transcriptional regulator. The full-length CAZFP1 had no transcriptional activation activity, whereas the C-terminal region of CAZFP1 had transactivation activity. The CAZFP1 transcripts were constitutively expressed in the pepper stem, root, flower and red fruit, but were not detectable in the leaf and green fruit. The CAZFP1 transcripts accumulated earlier than the CAZFP1 (PR-1) gene in the incompatible interaction of the pepper leaves with X. campestris pv. vesicatoria . The CAZFP1 transcripts were significantly induced in the systemic, uninoculated leaf tissues early after inoculation with bacterial pathogens, but gradually declined thereafter. The CAZFP1 transcripts were localized, and confined to the phloem cells of the vascular bundle in the pepper leaf midrib in response to Colletotrichum. coccodes infection, ethylene and abscisic acid. The CAZFP1 gene was also induced much earlier by abiotic elicitors and environmental stresses, compared with the CAZFP1 gene. Overexpression of the CAZFP1 gene in the transgenic Arabidopsis plants enhanced not only the resistance against infection by Pseudomonas syringae pv. tomato, but also the drought tolerance. These results suggest that the CAZFP1 gene functions as an early-defense gene to enhance disease resistance and drought tolerance.

Amino Acid Sequence↗