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PubMed1998

Cell fate and cell differentiation status in the Arabidopsis root.

Post-embryonic development in plants is mainly achieved by its meristems. Within the Arabidopsis root meristem, both the fate and origin of its cells can be predicted with high accuracy. Mutants defective in the determination of root cell fates show that the corresponding genes are first required during embryogenesis. The sub-specification of cell fates, such as during epidermal root hair formation, involves transcription factors and phytohormones. In the Arabidopsis root, initial cell fate specification events must be followed by position-dependent reinforcement of cellular identity. A major question remains as to whether the signals that are involved in initiating the cellular pattern are the same or different from the signals used to reinforce it. The integrity of the root meristem is kept by balancing cell proliferation and cell differentiation, and differentiation-inhibiting signals originating from the quiescent centre are involved.

Arabidopsis↗
PubMed1994

Root nodulation of Sesbania rostrata.

The tropical legume Sesbania rostrata can be nodulated by Azorhizobium caulinodans on both its stem and its root system. Here we investigate in detail the process of root nodulation and show that nodules develop exclusively at the base of secondary roots. Intercellular infection leads to the formation of infection pockets, which then give rise to infection threads. Concomitantly with infection, cortical cells of the secondary roots dedifferentiate, forming a meristem which has an "open-basket" configuration and which surrounds the initial infection site. Bacteria are released from the tips of infection threads into plant cells via "infection droplets," each containing several bacteria. Initially, nodule differentiation is comparable to that of indeterminate nodules, with the youngest meristematic cells being located at the periphery and the nitrogen-fixing cells being located at the nodule center. Because of the peculiar form of the meristem, Sesbania root nodules develop uniformly around a central axis. Nitrogen fixation is detected as early as 3 days following inoculation, while the nodule meristem is still active. Two weeks after inoculation, meristematic activity ceases, and nodules then show the typical histology of determinate nodules. Thus, root nodule organogenesis in S. rostrata appears to be intermediate between indeterminate and determinate types.

Cell Differentiation↗
PubMed2000

Isolation and molecular characterisation of the gene encoding the cytoplasmic ribosomal protein S28 in Prunus persica [L.]] Batsch.

RT-PCR was performed on peach (Prunus persica [L.] Batsch) RNA to isolate cDNAs corresponding to transcripts which are differentially expressed in leaves borne on basal and apical shoots. A gene was identified which was more highly expressed in the leaves of basal shoots, and codes for the cytoplasmic protein S28 present in the small ribosomal subunit. The 5' leader regions of RPS28 mRNAs were found to harbour 8-11 pyrimidine tracts, which suggested similarities to regulatory stretches that control the translation of mRNAs for ribosomal proteins in animals. The peach S28 is encoded by two intron-containing genes, which are both transcribed in mitotically active tissues such as developing leaves and roots. In situ hybridisation to shoot vegetative apices and the measurement of nucleus/nucleolus ratios indicated that RPS28 expression was confined to areas undergoing active cell division. The mature RPS28 mRNA was detected as a single species in actively dividing tissues such as apical tips, developing leaves, vegetative buds, stamens, developing fruits and roots. In contrast, accumulation of a precursor RNA, in the presence of the mature product, was found in fully expanded leaves and subtending stems, while only the precursor species was detected in several late-stage tissues. This phenomenon suggested that expression of the mature RNA is controlled at the level of splicing and turnover of the precursor RNA. This is similar to the mode of regulation of ribosomal protein genes in animals.

Amino Acid Sequence↗
PubMed2001

Role of biologic glue repair of proximal aortic dissection in the development of early and midterm redissection of the aortic root.

BACKGROUND: Redissection of the aortic root after supracommissural aortic graft replacement with reapproximation of the layers of the dissected aortic root is relatively rare. Causes and surgical treatment of this lesion remain controversial. METHODS: From January 1983 to September 2000, 130 patients had emergency operation for acute type A aortic dissection. Of them, 57 patients underwent root reconstruction using biologic glues and 4 patients (7.0%) developed redissection of the aortic root associated with moderate to severe aortic regurgitation 5 to 27 months after the initial operation. In all patients, the proximal false lumen was obliterated with infusion of gelatin-resorcinol-formaldehyde (GRF) glue or BioGlue and the aorta was reinforced with Teflon felt strip or Surgicel placed on its outside wall. RESULTS: During reoperation, the noncoronary aortic sinus was found to be redissected in all patients with the dissection extending retrogradely to the aortic annulus. This resulted in aortic regurgitation with prolapse of the noncoronary cusp because the proximal suture line dehisced. Histopathology showed disappearance of the nuclei of the medial smooth muscle cells, suggesting tissue necrosis at the site of GRF glue application. The lesions were treated successfully with full root replacement using a freestyle heterograft bioprosthesis or a composite graft prosthesis. CONCLUSIONS: The use of biologic glues for reapproximating the layers of the dissected aortic root is associated with a certain amount of risk of aortic wall necrosis. Therefore, care should be taken to ensure proper use of these glues. Full root replacement could be a preferable technique for treating redissection of the aortic root.

Adult↗
PubMed2001

Identification of a cDNA clone encoding for a galactose-binding lectin from peanut (Arachis hypogaea) seedling roots.

A cDNA clone obtained from developing peanut (Arachis hypogaea) seedling roots, when expressed in Escherichia coli and insect cells (Sf9) gave a 29 kDa subunit protein. The native recombinant protein agglutinates neuraminidase treated human erythrocytes and the agglutination is inhibited by galactose. Nucleotide sequence and predicted amino acid sequence analyses indicate that it is different from peanut seed (PNA and SGL) and nodule (NGLa and NGLb) galactose-binding lectins.

Amino Acid Sequence↗
PubMed2003

The association of peroxisomes with the developing cell plate in dividing onion root cells depends on actin microfilaments and myosin.

We have investigated changes in the distribution of peroxisomes through the cell cycle in onion ( Allium cepa L.) root meristem cells with immunofluorescence and electron microscopy, and in leek ( Allium porrum L.) epidermal cells with immunofluorescence and peroxisomal-targeted green fluorescent protein. During interphase and mitosis, peroxisomes distribute randomly throughout the cytoplasm, but beginning late in anaphase, they accumulate at the division plane. Initially, peroxisomes occur within the microtubule phragmoplast in two zones on either side of the developing cell plate. However, as the phragmoplast expands outwards to form an annulus, peroxisomes redistribute into a ring immediately inside the location of the microtubules. Peroxisome aggregation depends on actin microfilaments and myosin. Peroxisomes first accumulate in the division plane prior to the formation of the microtubule phragmoplast, and throughout cytokinesis, always co-localise with microfilaments. Microfilament-disrupting drugs (cytochalasin and latrunculin), and a putative inhibitor of myosin (2,3-butanedione monoxime), inhibit aggregation. We propose that aggregated peroxisomes function in the formation of the cell plate, either by regulating hydrogen peroxide production within the developing cell plate, or by their involvement in recycling of excess membranes from secretory vesicles via the beta-oxidation pathway. Differences in aggregation, a phenomenon which occurs in onion, some other monocots and to a lesser extent in tobacco BY-2 suspension cells, but which is not obvious in the roots of Arabidopsis thaliana (L.) Heynh., may reflect differences within the primary cell walls of these plants.

Actin Cytoskeleton↗
PubMed2003

The over-expression of an alfalfa RING-H2 gene induces pleiotropic effects on plant growth and development.

The alfalfa MsRH2-1 gene encodes a small protein with a RING-H2 motif and an N-terminal transmembrane domain. The transcript can be found in all tested plant organs, but roots and nodules show the highest levels of RH2-1 mRNA accumulation. Promoter-GUS fusion studies demonstrate that the activity of this gene is closely correlated with development of lateral roots (in alfalfa and Arabidopsis) and symbiotic nodules (in alfalfa). Although antisense-expressing alfalfa plants did not show a significantly different phenotype from the control plants, by contrast, when the level of the MsRH2-1 RNA was raised by introducing the coding part of the gene under the control of the CaMV promoter, both the transgenic alfalfa and Arabidopsis lines exhibited dramatic alterations in plant morphology, including shorter stature, increased apical dominance, leaf hyponasty, and inhibition of leaf venation and lateral root development. Moreover, nodulation of transgenic alfalfa roots was delayed and partially inhibited, and some of the Arabidopsis lines showed abnormal floral development. The nature of pleiotropic developmental phenotypes suggests a hormonal basis. The possible connection between MsRH2-1 function and substrate specific degradation via the ubiquitin pathway involved in auxin signaling is discussed.

Amino Acid Sequence↗
PubMed2003

Phenolic diterpenes, flavones, and rosmarinic acid distribution during the development of leaves, flowers, stems, and roots of Rosmarinus officinalis. Antioxidant activity.

The distribution of six compounds with three different polyphenol skeletons have been studied in Rosmarinus officinalis: phenolic diterpenes (carnosic acid, carnosol, and 12-O-methylcarnosic acid), caffeoyl derivatives (rosmarinic acid), and flavones (isoscutellarein 7-O-glucoside and genkwanin), each showing a characteristic behavior and distribution during the vegetative cycle. Only in leaves were all six compounds present, and the highest accumulation rate was related with the young stages of development. Rosmarinic acid showed the highest concentrations of all the polyphenols in all organs. The distribution of this acid in leaves, flowers, and stems suggests that in the first stages of flower growth, levels were due to in situ biosynthesis, and in the last stages, the contribution of transport phenomena was increased. The antioxidant activity of six extracts with different polyphenolic composition was evaluated in aqueous and lipid systems. The results clearly suggest that rosemary extracts are excellent antioxidants in both aqueous and lipid systems.

Abietanes↗
PubMed1992

Selective dependence of mammalian dorsal root ganglion neurons on nerve growth factor during embryonic development.

We have investigated the NGF dependence of dorsal root ganglion (DRG) neurons in mammals using a paradigm of multiple in utero injections of a high titer anti-NGF antiserum. We have determined the specificity of our antiserum in relation to other members of the NGF neurotrophin family and found no cross-reactivity with brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3). To identify various classes of DRG neurons, we have stained their characteristic central projections with Dil. We show here that the NGF dependence of DRG neurons is strikingly selective. Although a majority of DRG neurons are lost after NGF deprivation during embryonic life, these are almost exclusively small diameter neurons that project to laminae I and II of the dorsal horn and presumably subserve nociception and thermoreception. Larger neurons that project to more ventral spinal laminae and subserve other sensory modalities do not require NGF for survival. These NGF-independent DRG neurons likely require one of the more recently identified neurotrophins, BDNF or NT-3.

Afferent Pathways↗
PubMed1989

Induction of alcohol dehydrogenase and lactate dehydrogenase in hypoxically induced barley.

In barley (Hordeum vulgare L.), alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH) are induced by anaerobiosis in both aleurone layers and roots. Under aerobic conditions, developing seeds of cv Himalaya accumulate ADH activity, which survives seed drying and rehydration. This activity consists almost entirely of the ADH1 homodimer. Activity of LDH also increases during seed development, but the level of activity in dry or rehydrated seeds is very low, indicating that this enzyme may not be involved in anaerobic glycolysis during the initial stages of germination. In contrast to ADH, the LDH isozymes present in developing seeds are similar to those found in uninduced and induced roots. Developmental expression of ADH and LDH was monitored from 0 to 24 days postgermination. Neither activity was induced to any extent in the germinating seeds; however, both enzymes were highly induced by anoxia in root tissue during development. Based on gel electrophoresis, this increase in activity results from the differential expression of different Adh and Ldh genes in root tissue. The changes in ADH and LDH activity levels were matched by changes in the amount of these particular proteins, indicating that the increase in activity results from de novo synthesis of these two proteins. The level of inducible LDH activity in an ADH1(-) mutant was not found to differ from cv Himalaya. We suggest that although the ADH(-) plants are more susceptible to flooding, they are not capable of responding to the lack of ADH1 activity by increasing the amount of LDH activity in root tissue.

Journal Article↗
PubMed2003

Transcript profiling coupled with spatial expression analyses reveals genes involved in distinct developmental stages of an arbuscular mycorrhizal symbiosis.

The formation of symbiotic associations with arbuscular mycorrhizal (AM) fungi is a phenomenon common to the majority of vascular flowering plants. Here, we used cDNA arrays to examine transcript profiles in Medicago truncatula roots during the development of an AM symbiosis with Glomus versiforme and during growth under differing phosphorus nutrient regimes. Three percent of the genes examined showed significant changes in transcript levels during the development of the symbiosis. Most genes showing increased transcript levels in mycorrhizal roots showed no changes in response to high phosphorus, suggesting that alterations in transcript levels during symbiosis were a consequence of the AM fungus rather than a secondary effect of improved phosphorus nutrition. Among the mycorrhiza-induced genes, two distinct temporal expression patterns were evident. Members of one group showed an increase in transcripts during the initial period of contact between the symbionts and a subsequent decrease as the symbiosis developed. Defense- and stress-response genes were a significant component of this group. Genes in the second group showed a sustained increase in transcript levels that correlated with the colonization of the root system. The latter group contained a significant proportion of new genes similar to components of signal transduction pathways, suggesting that novel signaling pathways are activated during the development of the symbiosis. Analysis of the spatial expression patterns of two mycorrhiza-induced genes revealed distinct expression patterns consistent with the hypothesis that gene expression in mycorrhizal roots is signaled by both cell-autonomous and cell-nonautonomous signals.

Expressed Sequence Tags↗
PubMed1997

Onset of CNTFRalpha expression and signal transduction during neurogenesis in chick sensory dorsal root ganglia.

The expression of ciliary neurotrophic factor receptor alpha (CNTFRalpha) was investigated in the developing chick dorsal root ganglion (DRG) using affinity-purified anti-CNTFRalpha antibodies. At thoracic levels, CNTFRalpha-immunoreactivity (CNTFRalpha-IR) was first observed at stage 19 (E3) in cells with neuronal morphology. CNTFRalpha-IR is restricted to the neuronal lineage in the DRG throughout development. CNTFRalpha expression precedes that of neuron-specific beta tubulin, Hu antigen, and Q211 antigen, which are markers expressed in developing sensory neurons. [3H]Thymidine-labeling studies showed the onset of CNTFRalpha expression during terminal mitosis of sensory neuron precursors, making CNTFRalpha the earliest known neuronal marker in the DRG. CNTFRalpha-mediated signal transduction was demonstrated in E7 and E11 DRG neuron cultures by CNTF-induced STAT3 phosphorylation. Although low ligand concentrations (5 pM) elicit STAT3 phosphorylation in E7 and E11 DRG neurons, a survival response is only observed in neurons from E11 DRG. This implicates a complex readout mechanism downstream of STAT3 phosphorylation leading to different cellular responses that depend on the age of the DRG neuron. These results argue against a role of CNTFRalpha ligands in the control of early neuron survival but are compatible with other functions in neurogenesis and sensory neuron development.

Animals↗
PubMed1999

Effect of Wild-Type and Mutant Plant Growth-Promoting Rhizobacteria on the Rooting of Mung Bean Cuttings.

Mung bean cuttings were dipped in solutions of wild type and mutant forms of the plant growth-promoting rhizobacterium Pseudomonas putida GR12-2 and then incubated for several days until roots formed. The bacteria P. putida GR12-2 and P. putida GR12-2/aux1 mutant do not produce detectable levels of the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, whereas P. putida GR12-2/acd36 is an ACC deaminase minus mutant. All bacteria produce the phytohormone indole-3-acetic acid (IAA), and P. putida GR12-2/aux1 overproduces it. Treatment of cuttings with the above-mentioned bacteria affected the rates of ethylene production in the cuttings in a way that can be explained by the combined effects of the activity of ACC deaminase localized in the bacteria and bacterial produced IAA. P. putida GR12-2 and P. putida GR12-2/acd36-treated cuttings had a significantly higher number of roots compared with cuttings rooted in water. In addition, the wild type influenced the development of longer roots. P. putida GR12-2/aux1 stimulated the highest rates of ethylene production but did not influence the number of roots. These results are consistent with the notion that ethylene is involved in the initiation and elongation of adventitious roots in mung bean cuttings.

Journal Article↗
PubMed2003

Somatic embryogenesis and plant regeneration from seeds of wild Dicentra spectabilis (L.) LEM.

Regeneration via somatic embryogenesis from callus was studied in Dicentra spectabilis. To obtain somatic embryogenic callus, we cultured D. spectabilis seeds on MS basal media supplemented with various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D). The highest percentage of embryogenic callus formation was observed on media containing 1.0 mg/l 2,4-D under dark conditions. Somatic embryogenesis was studied by transferring the callus onto MS basal medium containing different concentrations (0.0, 0.1, 0.5, 1.0, 2.0 mg/l) of KIN (kinetin) and/or BAP. Somatic embryogenesis on MS basal media with 1.0 mg/l of KIN was excellent under light conditions. Somatic embryos were rooted by transferring them to half-strength MS basal media containing 2 g/l Phytagel. About 64.2% of the somatic embryos converted to rooted plantlets, 4% showed secondary embryogenesis and 31.8% did not develop and died. Rooted plantlets showed a 46% survival rate when acclimatized ex vitro.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2026

High-efficiency genome-editing, transgene evaluation, and antimicrobial efficacy testing using Citrus medica L. hairy roots.

Huanglongbing (HLB) disease, associated with the fastidious bacterium Candidatus Liberibacter asiaticus (CLas), has a significant impact on citrus production worldwide. Conventional biochemical and genetic evaluation studies to identify potential disease resistance strategies have been mainly hindered due to the inability to culture CLas in a defined medium and the general recalcitrance of Citrus cultivars (grapefruits and oranges) to Agrobacterium-mediated plant transformation. We previously demonstrated the utility of plant hairy roots to co-cultivate CLas. In this study, we developed a hairy root transformation system using citron (Citrus medica L.), which is highly amenable to Rhizobium-mediated hairy root transformation. The explant survival and hairy root transformation efficiencies were up to 100% and 73%, respectively, and transgenic roots can be attained in as little as 30-60 days. We demonstrate the utility of this citron-based hairy root transformation for rapid CRISPR/Cas9-mediated gene editing, transgene evaluation, and antimicrobial efficacy testing. The citron-based hairy root transformation system will significantly help the research community to speed-track the assessment of potential HLB disease resistance strategies.

Citrus↗
PubMed1976

Treatment of non-vital permanent incisors with calcium hydroxide. VI. A clinical, microbiological and radiological evaluation of treatment in one sitting of teeth with mature or immature root.

The purpose of the investigation was clinically, microbiologically and radiologically to assess the effect of calcium hydroxide as a temporary root-filling inserted in the same sitting as root canal debridement in non-vital permanent incisors with mature and immature root, infected or uninfected root canal and with or without radiologically demonstrated periapical bone changes. The material consisted of 141 teeth divided in 3 groups in which mechanical cleansing was accompanied by flushing with sterile saline and sodium hypochlorite solutions giving 0.5% or 5.0% active chlorine, respectively. Microbiological samples were taken from root canals after extirpation of necrotic pulp tissue, after completed cleansing of the root canal and 3 and 6 month after treatment. Results of treatment were evaluated from the radiographs taken before treatment and at the 3 and 6 month follow-ups. Complication, pain and an abscess, occurred in 2 cases, 2 and 5 days, respectively, after treatment. No statistical correlation between occurrence of samples that gave growth, taken from the root canals at 3 (8%) or 6-month control (9%) and 1) bacteriological status of the root canal prior to filling with calcium hydroxide, 2) the development of the root or 3) periapical healing at 3 or 6 month follow-up could be ascertained. Periapical bone healing at the end of 6-months observation period was noted in 61 teeth (46%), regression of periapical bone lesions in 64 (49%) and no periapical healing in 6 (5%). The only difference in healing pattern, statistically significant on 0.1% level, was found in the group of teeth flushed with 5.0% sodium hypochlorite. At 3 month control they showed percentually less cases with regression and more cases with no healing of periapical bone lesions than the teeth in the other two groups. It was concluded that treatment in one sitting can be done routinely, irrespective of the initial status, in all those cases where no other treatment is possible. If the periodontium or the periapical bone are injured during cleansing procedures or if necrotic rests are not pressed out through the apical foramen, no complications after treatment need to be feared.

Adolescent↗
PubMed1991

A study on citric acid as a proposed replacement resorption inhibitor.

The material consisted of 36 one-rooted immature teeth in 6 mongrel dogs. 12 teeth were immediately replanted after extraction, while 24 teeth were extracted and stored dry for 120 min before re- or autotransplantation. Root planing and topical citric acid treatment of the root of dry-stored teeth did not prevent the development of progressive root resorption and ankylosis, not even when special care was taken to prevent damage to the superficial, demineralized layer of the root during and after the transplantation procedures in an experimental model, which included autotransplantation of teeth to sockets, which were much larger than their original sockets.

Alveolar Process↗