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PubMed1994

A molecular marker for lateral root initiation: the RSI-1 gene of tomato (Lycopersicon esculentum Mill) is activated in early lateral root primordia.

The frequency of lateral root initiation in tomato (Lycopersicon esculentum Mill cv. VFN8) seedling roots is increased over eightfold in response to 1.6 microM alpha-naphthalene-acetic acid (NAA). To identify genes that are activated during lateral root initiation, a cDNA library was made with RNA from roots treated with auxin and differentially screened with radioactive probes made from RNA isolated from treated and untreated roots. A cDNA clone, TR132, was identified that hybridized to a transcript that was induced within 4 h of auxin treatment and increased tenfold by 72 h. A gene (RSI-1) corresponding to the TR132 cDNA was cloned and characterized with regard to its nucleotide sequence, transcription start site and chromosomal map position. Approximately 1 kb of the 5' flanking DNA was linked to the beta-glucuronidase (GUS) protein coding region and tested for expression in transgenic tomato seedlings. GUS activity was observed in both lateral and adventitious root initials, including very early initials, and persisted until shortly after the lateral emerged from the parent tissue. In roots from seedlings with high activity, GUS expression was also observed in the root cap and vascular tissue. The predicted RSI-1 protein is rich in cysteine, lysine and proline, and includes an N-terminal region with characteristics of a signal peptide. The putative mature protein exhibits 79% amino acid identity to a protein encoded by a gene (GAST1) that is induced by gibberellic acid in tomato shoots.

Amino Acid Sequence↗
PubMed1990

Agrobacterium tumefaciens T-DNA gene 6b stimulates rol-induced root formation, permits growth at high auxin concentrations and increases root size.

All Agrobacterium tumefaciens strains studied up to now transfer an active 6b gene to plant cells. However, the role of this gene in natural tumour induction is unknown. Various effects of 6b on plant cell growth have been described, but the precise mechanism by which 6b causes these effects has not been elucidated. Earlier experiments indicated that the 6b gene might increase auxin sensitivity as do the A. rhizogenes rol genes. The 6b gene from Tm4 (T-6b) was therefore compared with the rolB and rolABC genes. Although T-6b was unable to induce root formation, it strongly interfered with root induction and root elongation. In rolABC/T-6b coinfection experiments on carrots, T-6b-transformed cells stimulated root outgrowth of rolABC-transformed cells, indicating that the biologically active T-6b product is diffusible. Carrot rolABC roots containing the T-6b gene rapidly developed into unorganized calli. Nicotiana rustica roots with rolABC and T-6b continued their development, but became very large. Fragments of such roots formed callus at alpha-naphthaleneacetic acid concentrations which inhibited growth of rolABC and normal root fragments, suggesting that the role of 6b genes in natural tumour induction may be to reduce the inhibitory effects of high auxin levels and to keep cells in an undifferentiated state.

Cloning, Molecular↗
PubMed1986

Induction of ELF transmembrane potentials in relation to power-frequency electric field bioeffects in a plant root model system. I. Relationship between applied field strength and cucurbitaceous root growth rates.

Seminal roots of Cucumis sativus and Cucurbita maxima were exposed to 60 Hz electric fields of 100-500 V X m-1 in a conducting aqueous inorganic growth medium. Root growth rates were measured to produce a dose-response relationship for each species. The species were selected for study because of their familial relationship, reported sensitivity to 60 Hz, 360 V X m-1 electric fields, and differing average root cell sizes. The latter characteristic influences the magnitude of ELF membrane potentials induced by constant-strength applied electric fields, but does not affect the magnitude of the electric field strength tangent to the cell surface. The difference in average root cell size between C. sativus (smaller cells) and C. maxima (larger cells) was used to evaluate two alternate hypotheses that the observed effect on root growth is stimulated by the electric field tangent to the cell surface, or a field-induced perturbation in the normal transmembrane potential of the cells. The results of the dose-response relationship studies are qualitatively consistent with the hypothesis that the effect is elicited by induced transmembrane potentials. The smaller-celled roots showed a substantially higher response threshold [C. sativus; E0TH approximately 330 V X m-1] than did the larger-celled species [C. maxima; E0TH approximately 200 V X m-1]. At field strengths above the response thresholds in both species, the growth rate of C. sativus roots was less affected than that of C. maxima roots exposed to the same field strength.

Cell Division↗
PubMed2006

Root replacement using stentless valves in the small aortic root: a propensity score analysis.

BACKGROUND: Root replacement using a stentless bioprosthesis may be the optimal approach to avoid patient-prosthesis mismatch in patients with a small aortic root. Primary root replacement, however, is considered to be associated with increased surgical risk. We compared early outcome of full root replacement with a stentless bioprosthesis with that of aortic valve replacement with a stented bioprosthesis using propensity score-matching analysis. METHODS: Of 231 patients undergoing elective, first-time aortic valve replacement with a small root (< or = 22 mm), 120 patients were selected using propensity score-matching analysis. They underwent either root replacement using a 23-mm stentless bioprosthesis (stentless group, n = 60) or supra-annular aortic valve replacement using a 21-mm stented bioprosthesis (stented group, n = 60). Preoperative characteristics and frequency of concomitant operations were identical. RESULTS: Duration of operation (196 +/- 54 versus 174 +/- 49 minutes), cardiopulmonary bypass (112 +/- 36 versus 91 +/- 33 minutes), and aortic cross-clamping (76 +/- 21 versus 61 +/- 21 minutes) were significantly longer in the stentless group. However, the need for perioperative transfusion and the incidence of postoperative reexploration for bleeding (3% versus 8%) was lower, and ventilation time was shorter. Mean duration of intensive care and hospital stay were also significantly shorter (2.3 +/- 1.7 versus 4.0 +/- 3.9 days, 8.9 +/- 3.1 versus 12.4 +/- 5.7 days). In-hospital mortality was identical (5% each). No independent predictor for in-hospital mortality was identified. CONCLUSIONS: Full root replacement using a stentless bioprosthesis does not increase postoperative morbidity or mortality of aortic valve replacement and may be advantageous in patients with a small aortic root.

Aged↗
PubMed1997

Loss of dorsal root ganglion cells concomitant with dorsal root axon sprouting following segmental nerve lesions.

Tight ligation of the fifth and sixth lumbar segmental nerves in the rat provides a model of neuropathic pain. We used this model to assess the changes in primary afferent input to the dorsal horn in neuropathic pain syndromes. Dorsal roots and ganglia were examined for up to 32 weeks following segmental nerve ligation. Stereologic and morphometric techniques revealed a notable decrease in the numbers of dorsal root ganglion cells and unmyelinated dorsal root axons by six weeks post-injury. By 32 weeks following segmental nerve ligations, the numbers of dorsal root ganglion cells have dropped to 50% of pre-ligation levels while the numbers of dorsal root axons have increased to normal levels predominantly due to sprouting of myelinated fibres. These findings indicate that although there is a great loss of dorsal root ganglion cells, there is dramatic sprouting of myelinated fibres and possibly some sprouting of unmyelinated fibres in the dorsal roots. Additionally, a difference in the responses of unmyelinated and myelinated fibres to this peripheral nerve injury is revealed. These changes in dorsal root ganglion cells and their central axons may underlie certain aspects of abnormal pain syndromes because of changes in the types and quantity of input the dorsal horn receives.

Animals↗
PubMed1994

Correlation of Pectin Methylesterase Activity in Root Caps of Pea with Root Border Cell Separation.

We tested predictions of the hypothesis that pectin methylesterase in the root cap plays a role in cell wall solubilization leading to separation of root border cells from the root tip. Root cap pectin methylesterase activity was detected only in species that release large numbers of border cells daily. In pea (Pisum sativum) root caps, enzyme activity is correlated with border cell separation during development: 6-fold more activity occurs during border cell separation than after cell separation is complete. Higher levels of enzyme activity are restored by experimental induction of border cell separation. A corresponding increase in transcription of a gene encoding root cap pectin methylesterase precedes the increase in enzyme activity. A dramatic increase in the level of soluble, de-esterified pectin in the root tip also is correlated with pectin methylesterase activity during border cell development. This increase in acidic, de-esterified pectin during development occurs in parallel with a decrease in cell wall/apoplastic pH of cells in the periphery of the root cap.

Journal Article↗
PubMed1971

Deoxyribonucleic Acid synthesis in root cap cells of cultured roots of convolvulus.

Isolated cultured roots of Convolvulus arvensis L. were incubated in 0.2 microcurie per milliliter methyl-(3)H-thymidine for 14 hours, for 64 hours, or for 14 hours followed by transfer to fresh nutrient medium without tritiated thymidine. Autoradiographs of serial, longitudinal sections of roots which were continuously incubated with tritiated thymidine showed that cells of the root cap columella did not undergo DNA synthesis after their formation from the root cap initials. In roots pulse-labeled with tritiated thymidine, the movement of labeled cells through the root cap columella was followed. Labeled cells were displaced at a constant rate of 72 microns per day over a period of 6 to 9 days before they were sloughed off from the root cap. The specialized role of the root cap cells in relation to their distinctive metabolism and longevity is discussed.

Journal Article↗
PubMed1981

A split-root technique for measuring root water potential.

Water encounters various resistances in moving along a path of decreasing potential energy from the soil through the plant to the atmosphere. The reported relative magnitudes of these pathway resistances vary widely and often these results are conflicting. One reason for such inconsistency is the difficulty in measuring the potential drop across various segments of the soil-plant-atmosphere continuum. The measurement of water potentials at the soil-root interface and in the root xylem of a transpiring plant remains a challenging problem.In the divided root experiment reported here, the measured water potential of an enclosed, nonabsorbing branch of the root system of young corn (Bonanza) plants to infer the water potential of the remaining roots growing in soil was used. The selected root branch of the seedling was grown in a specially constructed Teflon test tube into which a screen-enclosed thermocouple psychrometer was inserted and sealed to monitor the root's water potential. The root and its surrounding atmosphere were assumed to be in vapor equilibrium.

Journal Article↗
PubMed1987

Errors in the Measurement of Root Pressure and Exudation Volume Flow Rate Caused by Damage during the Transfer of Unsupported Roots between Solutions.

Plants of Zea mays were grown with their roots confined to growing tubes, consisting of cylindrical or spherical glass tubes fitted at the bottom with a stopcock. Nutrient solution was circulated past the roots, and when a plant was 21 to 25 days old, the stopcock was closed, the root excised from the plant and connected to an apparatus which measured root pressure and exudation volume flow rate. The stopcock was opened and solution was again circulated through the growing tube without dropping the level of the liquid bathing the root in the process. Measurements of pressure and flow rate were made continuously during a period in which the solution was replaced, first by draining and refilling the tube in situ, and second by replacing the growing tube with a beaker of solution. Both these manipulations caused at least temporary and frequently permanent drops in root pressure and flow rate. Plants were also grown in cylindrical tubes with a support medium of either glass beads or Raschig rings which filled the growing tubes. It is shown that the solution bathing these roots could be repeatedly replaced by draining and refilling with no visible effect on the measurements. It is recommended, therefore, that in future, support be provided for the roots of all experimental plants grown by solution culture.

Journal Article↗
PubMed1996

Hormones act downstream of TTG and GL2 to promote root hair outgrowth during epidermis development in the Arabidopsis root.

The Arabidopsis root produces a position-dependent pattern of hair-bearing and hairless cell types during epidermis development. Five loci (TRANSPARENT TESTA GLABRA [TTG], GLABRA2 [GL2], ROOT HAIR DEFECTIVE6 [RHD6], CONSTITUTIVE TRIPLE RESPONSE1 [CTR1], and AUXIN RESISTANT2 [AXR2]) and the plant hormones ethylene and auxin have been reported to affect the production of root hair and hairless cells in the Arabidopsis root. In this study, genetic, molecular, and physiological tests were employed to define the roles of these loci and hormones. Epistasis tests and reporter gene studies indicated that the hairless cell-promoting genes TTG and GL2 are likely to act early to negatively regulate the ethylene and auxin pathways. Studies of the developmental timing of the hormone effects indicated that ethylene and auxin pathways promote root hair outgrowth after cell-type differentiation has been initiated. The genetic analysis of ethylene-and auxin-related mutations showed that root hair formation is influenced by a network of hormone pathways, including a partially redundant ethylene signaling pathway. A model is proposed in which the patterning of root epidermal cells in Arabidopsis is regulated by the cell position-dependent action of the TTG/GL2 pathway, and the ethylene and auxin hormone pathways act to promote root hair outgrowth at a relatively late stage of differentiation.

Amino Acids↗
PubMed2004

Exposure of roots of cucumber (Cucumis sativus) to low temperature severely reduces root pressure, hydraulic conductivity and active transport of nutrients.

When root temperature dropped below 25 degrees C, there was a sharp drop in the root pressure (P(r)) and hydraulic conductivity of excised roots (Lp(r)) of young cucumber (Cucumis sativus L.) seedlings as measured with the root pressure probe. A detailed analysis of root hydraulics provided evidence for a larger reduction in the osmotic component of Lp(r) (77%) in comparison with the hydrostatic component (34%) in response to the exposure of the root system to 13 degrees C. The activity of the plasma membrane H(+)-ATPase (EC 3.6.1.35) was reduced from 30 to 16 micro mol Pi mg(-1) protein h(-1) upon exposure to 8 degrees C for 1 day. Ultrastructural observations showed no evidence of loosening of the microstructure of endodermal cell walls in low temperature (LT)-treated roots. It is concluded that the rapid drop in the P(r) in response to LT is largely caused by a reduction in the activity of the plasma membrane H(+)-ATPase rather than by loosening of the endodermal wall which would cause substantial solute losses. On the other hand, water permeability of root cell membrane at LT was related to changes in the activity (open/closed state) of water channels.

Journal Article↗
PubMed1990

Characterization of Root Surface and Endorhizosphere Pseudomonads in Relation to Their Colonization of Roots.

An extensive colonization of the endorhizosphere by fluorescent pseudomonads was observed in tomato plants grown on artificial substrates. These studies reveal that a significantly higher percentage of pseudomonads obtained from the endorhizosphere (30%) reduced plant growth than those obtained from the root surface (4%). Lipopolysaccharide patterns, cell envelope protein patterns, and other biochemical characteristics indicated that Pseudomonas isolates obtained from the endorhizosphere are distinct from Pseudomonas isolates obtained from the root surface. Isolates from the endorhizosphere especially were able to recolonize the endorhizosphere of both sterile and nonsterile tomato roots. The ability of the endorhizosphere isolates to colonize the endorhizosphere significantly correlated with their agglutination by tomato root agglutinin but did not correlate with chemotaxis to seed exudates of tomato. No correlation between colonization of the endorhizosphere and agglutination by root agglutinin could be demonstrated for the root surface isolates. We propose that agglutination of specific Pseudomonas strains by root agglutinin is of importance in the initial phase of adherence of bacteria to the root surface.

Journal Article↗
PubMed1991

Early recognition in the Rhizobium meliloti-alfalfa symbiosis: root exudate factor stimulates root adsorption of homologous rhizobia.

Adsorption of Rhizobium meliloti to alfalfa roots before their infection and nodule formation shows the specificity of the symbiotic association (G. Caetano-Anollés and G. Favelukes, Appl. Environ. Microbiol. 52:377-382, 1986). The time course of specific adsorption of R. meliloti (10(3) to 10(4) cells per ml) to roots shows an initial lag period of 3 h, suggesting that either or both symbionts must become conditioned for the adsorption process. Preincubation of R. meliloti L5-30 for 3 h with dialyzed alfalfa root exudate (RE) markedly increased early adsorption of rhizobia to alfalfa roots. The activity in RE was linked to a nondialyzable, thermolabile, trypsin-sensitive factor(s), very different from the root-exuded flavonoid compounds also involved in early Rhizobium-legume interactions. The lack of activity in the RE from plants grown in 5 mM NO3- suggested its negative regulation by the nitrogen nutritional status of the plant. Preincubation of R. meliloti with heterologous clover RE did not stimulate adsorption of rhizobial cells to roots. A short pretreatment of RE with homologous (but not heterologous) strains eliminated the stimulatory activity from solution. The stimulation of adsorption of R. meliloti to alfalfa roots was strongly dependent on the growth phase of the rhizobia, being greater at the late exponential stage. Nevertheless, the capacity of R. meliloti L5-30 to eliminate from solution the stimulatory activity in RE appeared to be constitutive in the rhizobia. The low concentration of rhizobial cells used in these experiments was critical to detect the stimulation of adsorption. The early interaction of spontaneously released alfalfa root macromolecular factor(s) and free-living R. meliloti, which shows the specificity and regulatory properties characteristic of infection and nodulation, would be an initial recognition event in the rhizosphere which triggers the process of symbiotic association.

Bacterial Adhesion↗
PubMed1999

Urgent homograft aortic root replacement for aortic root abscess in infants and children.

OBJECTIVE: To assess the results of early homograft aortic root replacement in infants and children with an aortic root abscess. DESIGN: Descriptive study of all patients with an aortic root abscess during 1987-97, identified by retrospective review of the echocardiographic and surgical registries. SETTING: A tertiary referral centre. PATIENTS: Five patients (age 0.6 to 13 years; two female) were identified with an aortic root abscess. Four had no known pre-existing congenital heart abnormality. Three had a misleading presentation and were referred to our hospital with non-cardiac diagnoses (fulminant hepatic failure; adult respiratory distress syndrome; cerebrovascular accident). The other two presented with septicaemia and a murmur, respectively. Blood cultures identified Staphylococcus aureus (n = 3) and Streptococcus pneumoniae (n = 2). Aortic root abscess was diagnosed by transthoracic echocardiography. INTERVENTIONS: Homograft aortic root replacement with coronary reimplantation was performed urgently (median one day after diagnosis). RESULTS: Four patients survived. The youngest died following multiorgan failure, multiple aortic fistulae, three valve involvement, and extensive tissue destruction preventing mitral valve replacement (S pneumoniae). Two of the four survivors have required further surgery: mitral valve replacement (0.3 years later), and pulmonary autograft replacement of the homograft (8.3 years later). All survivors remain in sinus rhythm and New York Heart Association functional class I. CONCLUSIONS: Infective endocarditis should be considered in any child with severe septicaemia or embolic phenomena. Echocardiographic diagnosis of an aortic root abscess indicates uncontrolled infection and impending haemodynamic collapse. Homograft aortic root replacement can be performed successfully in critically ill children with active infection.

Abscess↗
PubMed1989

The mucilage secreted by roots and its possible role in cell-cell recognition for the adhesion of fungal pathogens to root surfaces of Zea mays L.

The outer cells of the roots of plants secrete a mucilage which lubricates the root and keeps it moist. The mucilage is secreted from the Golgi apparatus in vesicles which fuse at the plasma membrane. In maize roots a complex of at least three polysaccharides and glycoproteins are formed, some of which have a large proportion of fucose in their composition. The synthesis of these compounds can be readily monitored because fucose can be easily identified, and especially because exogenous fucose is not catabolized but is incorporated intact into the polymers. The synthesis of the polymers seems to be initiated in the endoplasmic reticulum in conjunction with polyprenoid oligosaccharides that contain fucose. Lipid-oligosaccharides of nine sugar residues can be obtained from the membrane preparations of the root cells. These compounds are polyprenyl diphosphate derivatives. A GDP-fucose:polyprenyl phosphate transfucosylase occurs in the endoplasmic reticulum, whereas fucosyl transferase that transfers fucose to a polymer occurs mainly in the Golgi apparatus. The indirect evidence suggests that oligosaccharides of polyprenyl diphosphate compounds are transferred to proteins, elaborated in the Golgi apparatus, and large molecular weight polysaccharides are finally exported as the mucus. Part of the mucus is acidic and in some respects resembles pectin. The presence of fucose in such large quantities in maize root mucilage suggested that this might have some significance for the recognition of these plants by parasitic root fungi. The adsorption of mucilage by pathogenic fungi was investigated with two types of fungi, a highly specialized ectotrophic root-infecting fungus, e.g. Phialophora radicicola and a vascular wilt fungus capable of attacking a great variety of tissues, e.g. Fusarium moniliforme. The adsorption of radioactively labelled and fluorescently labelled polymers by the pathogenic fungi was investigated. The character and proportion of fungal surfaces present in vitro were standardised by the production and semi-synchronous germination of populations of conidia. Changes in appearance of fungal walls, present before and after germination, were examined ultrastructurally. There was polyanionic material on hyphal but less on conidial surfaces of the ectotrophic root-infecting fungi. In contrast this material was present to similar extents on both hyphal and conidial surfaces of F. moniliforme.(ABSTRACT TRUNCATED AT 400 WORDS)

Adhesives↗
PubMed1995

Pulp and periodontal healing, root development and root resorption subsequent to transplantation and orthodontic rotation: a long-term study of autotransplanted premolars.

One hundred and eighteen premolars transplanted at a stage with 3/4 to 4/4 root development with a wide open apical foramen were followed with standardized clinical and radiographic techniques for signs of pulpal and periodontal ligament healing and root development. Pulp healing, evaluated first by radiographic presence of pulp canal obliteration, appeared to be an earlier sign of pulp healing than the detection of pulp vitality with an electrometric test. Continued root growth of premolars was seen in some cases. Complete arrest of root development was usually followed by development of the missing root structure at the donor site, indicating a separation of the Hertwig's epithelial root sheath. Orthodontic rotation performed on 11 premolars induced slight surface resorption and a significant shortening of tooth length (mean 1.2 mm), compared with nontreated but transplanted control teeth. However, the extent of the apical root resorption is of minor clinical importance, and is equivalent to what has been found in previous investigations of orthodontic treatment of nontransplanted premolars. Late pulp necrosis occurred in 2 of the 11 treated cases 6 years after transplantation and 5 years after orthodontic rotation. To prevent late pulp necrosis, orthodontic rotation is recommended after periodontal healing and before total pulp canal obliteration has taken place, i.e., 3 to 9 months after transplantation.

Bicuspid↗
PubMed1998

Root canal treatment of mandibular second premolar with four root canals: a case report.

The importance of an accurate diagnosis of the morphology of the root canal system is a prerequisite for successful root canal treatment and has been emphasized throughout the literature. Root canal morphology of premolar teeth, either maxillary or mandibular, and the discrepancies between first and second premolars, have been investigated and reported. A case report is presented of the root canal treatment of a mandibular second premolar with four root canals. As far as the reviewed literature revealed, up to three root canals in mandibular premolars have been reported. No previous report of a similar case of four root canals in a mandibular premolar was found.

Adult↗
PubMed1990

Vertical root fracture and dentin deformation in curved roots: the influence of spreader design.

The effect of lateral condensation using different tapered spreaders was evaluated. Curved mesiobuccal roots of maxillary molars were step-back prepared. Strain gauges applied to the root surfaces measured dentin deformation (distortion) during controlled lateral condensation with either fine finger or D11 spreaders. After obturation, roots were cross sectioned and analyzed under the stereomicroscope to detect the presence and pattern of fractures. The results showed no statistical difference between spreader designs as to mean distortion and the incidence of fractures; however several specimens in the D11 group showed high root distortion measurements. When fractures occurred, there were no consistent patterns of fracture in either spreader group. In conclusion, although there were no significant differences in mean deformation or fracture incidence in curved roots between the spreaders, the roots showing high deformation readings in the D11 group may be more susceptible to future vertical root fractures.

Dental Cavity Preparation↗