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At least 307 records · Page 17Linked to original sources
PubMed2002

Tissue specific localization of root infection by fungal pathogens: role of root border cells.

When roots of pea seedlings were inoculated uniformly with spores of Nectria haematocca or other pea pathogenic fungi, more than 90% developed lesions in the region of elongation within 3 days. More mature regions of most roots as well as the tip showed no visible signs of infection. Yet, microscopic observation revealed that 'mantles,' comprised of fungal hyphae intermeshed with populations of border cells, covered the tips of most roots. After physical detachment of the mantle, the underlying tip of most roots was found to be free of infection. Mantle-covered root tips did not respond to invasion of their border cells by activation of known defense genes unless there was invasion of the tip itself, as revealed by the presence of a lesion. Concomitant with the activation of defense genes was the induction of a cell-wall degrading enzyme whose expression is a marker for renewed production of border cells. Mantle formation did not occur in response to nonpathogens. The data are consistent with the hypothesis that border cells serve as a host-specific 'decoy' that protects root meristems by inhibiting fungal infection of the root tip.

Ascomycota↗
PubMed2002

Pseudomonas putida strain PCL1444, selected for efficient root colonization and naphthalene degradation, effectively utilizes root exudate components.

Previously, we have described the selection of a plant-bacterium pair that is efficient in rhizoremediating naphthalene pollution in microcosm studies. After repeated selection for efficient root tip colonization upon inoculation of seeds of grass cv. Barmultra and for stable and efficient growth on naphthalene, Pseudomonas putida PCL1444 was selected as the most efficient colonizer of Barmultra roots. Here, we report the analysis of Barmultra root exudate composition and our subsequent tests of the growth rate of the bacterium and of the expression of the naphthalene degradation genes on individual exudate components. High performance liquid chromatography analysis of the organic acid and sugar root-exudate components revealed that glucose and fructose are the most abundant sugars, whereas succinic acid and citric acid are the most abundant organic acids. Tn5luxAB mutants of PCL1444 impaired in naphthalene degradation appeared to be impaired in genes homologous to genes of the upper naphthalene degradation pathway present in various Pseudomonas strains and to genes of the lower pathway genes for naphthalene degradation in P. stutzeri. Highest expression for both pathways involved in naphthalene degradation during growth in minimal medium with the carbon source to be tested was observed at the start of the logarithmic phase. Naphthalene did not induce the upper pathway, but a different pattern of expression was observed in the lower pathway reporter, probably due to the conversion of naphthalene to salicylic acid. Salicylic acid, which is described as an intermediate of the naphthalene degradation pathway in many Pseudomonas strains, did induce both pathways, resulting in an up to sixfold higher expression level at the start of the logarithmic phase. When expression levels during growth on the different carbon sources present in root exudate were compared, highest expression was observed on the two major root exudate components, glucose and succinic acid. These results show an excellent correlation between successful naphthalene rhizoremediation by the Barmultra-P. putida PCL1444 pair and both efficient utilization of the major exudate components for growth and high transcription of the naphthalene catabolic genes on the major exudate components. Therefore, we hypothesize that efficient root colonizing and naphthalene degradation is the result of the applied colonization enrichment procedure.

Carbon↗
PubMed2003

The Medicago truncatula sucrose synthase gene MtSucS1 is activated both in the infected region of root nodules and in the cortex of roots colonized by arbuscular mycorrhizal fungi.

The MtSucS1 gene encodes a sucrose synthase (EC 2.4.1.13) in the model legume Medicago truncatula. To determine the expression pattern of this gene in different organs and in particular during root endosymbioses, we transformed M. truncatula with specific regions of MtSucS1 fused to the gusAint reporter gene. These fusions directed an induction to the vasculature of leaves, stems, and roots as well as to flowers, developing seeds, young pods, and germinating seedlings. In root nodules, strong promoter activity occurred in the infected cells of the nitrogen-fixing zone but was additionally observed in the meristematic region, the prefixing zone, and the inner cortex, including the vasculature. Concerning endomycorrhizal roots, the MtSucS1 promoter mediated strongest expression in cortical cells harboring arbuscules. Specifically in highly colonized root sections, GUS-staining was furthermore detected in the surrounding cortical cells, irrespective of a direct contact with fungal structures. In accordance with the presence of an orthologous PsSus1 gene, we observed a comparable regulation of MtSucS1 expression in the grain legume Pisum sativum in response to microbial symbionts. Unlike other members of the MtSucS gene family, the presence of rhizobial or Glomus microsymbionts significantly altered and enhanced MtSucS1 gene expression, leading us to propose that MtSucS1 is involved in generating sink-strength, not only in root nodules but also in mycorrhizal roots.

Base Sequence↗
PubMed2003

Gene silencing by expression of hairpin RNA in Lotus japonicus roots and root nodules.

We investigated the efficacy of self-complementary hairpin RNA (hpRNA) expression to induce RNA silencing in the roots and nodules of model legume Lotus japonicus, using hairy root transformation mediated by Agrobacterium rhizogenes. Transgenic lines that express beta-glucuronidase (GUS) by constitutive or nodule-specific promoters were supertransformed by infection of A. rhizogenes harboring constructs for the expression of hpRNAs with sequences complementary to the GUS coding region. GUS activity in more than 60% of the hairy roots was decreased or silenced almost completely. Silencing of the GUS gene was also observed in symbiotic nodules formed on hairy roots in both early and late stages of nodule organogenesis. These results indicate that transient RNA silencing by hairy root transformation provides a powerful tool for loss-of-function analyses of genes that function in roots and root nodules.

Gene Expression Regulation, Developmental↗
PubMed2000

Survival and regeneration of motoneurons in adult rats by reimplantation of ventral root following spinal root avulsion.

The present study examines whether reimplantation of the ventral root could prevent motoneuron death after root avulsion. In the control animals about 65% or 39% of motoneurons survived at 3 or 6 weeks post-injury respectively. More than 60% of them expressed nitric oxide synthase (NOS). In contrast, in animals with ventral root reimplantation, nearly 90% or 80% of motoneurons survived at 3 or 6 weeks post-injury respectively. Expression of NOS due to root avulsion was significantly inhibited in these experimental animals. More interestingly, about 80% of the surviving motoneurons were found to regenerate their axons into the reimplanted ventral root, and all of these regenerating motoneurons were NOS negative. Results of the present study show that reimplantation of avulsed ventral root can greatly enhance motoneuron survival and the surviving motoneurons can regrow their axons into the original ventral root.

Animals↗
PubMed1996

Results of the treatment of neurogenic bladder dysfunction in spinal cord injury by sacral posterior root rhizotomy and anterior sacral root stimulation.

PURPOSE: We evaluated the results of treatment of neurogenic bladder dysfunction in spinal cord injury by sacral posterior root rhizotomy and anterior sacral root stimulation using the Finetech-Brindley stimulator. MATERIALS AND METHODS: In 52 patients with spinal cord lesions and urological problems due to hyperreflexia of the bladder complete posterior sacral root rhizotomy was performed and a Finetech-Brindley sacral anterior root stimulator was implanted. All patients were evaluated and followed with a strict protocol. A minimal 6-month followup is available in 47 cases. RESULTS: Complete continence was achieved in 43 of the 47 patients with 6 months of followup. A significant increase in bladder capacity was attained in all patients. Residual urine significantly decreased, resulting in a decreased incidence of urinary tract infections. In 2 patients upper tract dilatation resolved. In 3 patients rhizotomy was incomplete and higher sectioning of the roots was necessary. One implant had to be removed because of infection. CONCLUSIONS: The treatment of neurogenic bladder dysfunction in spinal cord injury by anterior sacral root stimulation with the Finetech-Brindley stimulator in combination with sacral posterior root rhizotomy provides excellent results with limited morbidity.

Adolescent↗
PubMed1995

Chronic nerve root compression. Pathophysiologic mechanism of nerve root dysfunction.

STUDY DESIGN: The pathophysiologic changes of the spinal nerve root caused by chronic compression were assessed in the lumbar spine of the adult dog. METHODS: The seventh lumbar nerve root was banded with a Silastic tube 5 mm long and a 3 mm internal diameter, which is slightly larger than the diameter of the nerve root. Histologic and electrophysiologic studies as well as assessment of the blood-nerve barrier function in the nerve root were conducted at 24 hours through 12 months. RESULTS: The earliest findings were thickening of the dura mater and arachnoid membrane around the affected nerve root corresponding to the alteration of the blood-nerve barrier in the nerve root after 1 month. After 3 months, large myelinated fibers decreased in number and small newly formed fibers increased in the periphery of the fascicle. At 6 months, endoneurial fibrosis and Wallerian degeneration of nerve fibers became obvious. Compound action potentials and sensory nerve conduction velocity decreased by 3 and 12 months, respectively. Decrease in amplitude of the compressed action potential was identical to the period of decrease in large myelinated fibers, and nerve conduction velocity did not decrease as long as some large myelinated fiber remained until 12 months after tubing. CONCLUSION: Intraradicular edema caused by alteration of the blood-nerve barrier is the most important factor in the nerve root dysfunction due to chronic compression.

Animals↗
PubMed2006

Up-regulation of acid-sensing ion channel 3 in dorsal root ganglion neurons following application of nucleus pulposus on nerve root in rats.

STUDY DESIGN: Immunocytochemistry for acid-sensing ion channel 3 (ASIC3) in neurons of rat dorsal root ganglions (DRGs) from animals exposed to a model of lumbar disc herniation. OBJECTIVE: To examine expression of ASIC3 in DRGs and the effect of a sodium channel blocker applied to the nerve root in a rat model of lumbar disc herniation. SUMMARY OF BACKGROUND DATA: Radicular pain is a common symptom of lumbar disc herniation in human beings. A depolarizing sodium channel gated by protons during tissue acidosis, ASIC3, is specifically expressed in sensory neurons. It has been associated with cardiac ischemic and inflammatory pain. We often perform spinal nerve root block for radicular pain using a sodium channel blocker, such as lidocaine; however, it has been unclear whether the effective period of this treatment is usually longer than the expected duration of efficacy. METHODS: For the lumbar disc herniation model, nucleus pulposus was harvested from the tail and applied to the L5 nerve root, and the nerve roots were pinched. We evaluated mechanical allodynia in sham-operated animals and a disc herniation model. Immunohistochemistry was used to examine ASIC3 expression in L5 DRGs. Finally, the effect of lidocaine on pain and ASIC3 expression in the disc herniation model was examined. RESULTS: Animals exposed to the lumbar disc herniation model showed allodynia for 8 days, and ASIC3 immunoreactivity was up-regulated in DRG neurons. After administration of lidocaine to spinal nerve roots affected by disc herniation, ASIC3 immunoreactivity was down-regulated in DRG neurons, and the level of mechanical allodynia was significantly decreased for 8 days. CONCLUSIONS: Our results suggest that ASIC3 in DRG neurons may play an important role in nerve root pain caused by lumbar disc herniation. Lidocaine decreased ASIC3 expression in DRG neurons and pain associated with the disc herniation model.

Acid Sensing Ion Channels↗
PubMed2004

Root-to-shoot transport of sulfate in Arabidopsis. Evidence for the role of SULTR3;5 as a component of low-affinity sulfate transport system in the root vasculature.

Xylem transport of sulfate regulates distribution of sulfur in vascular plants. Here, we describe SULTR3;5 as an essential component of the sulfate transport system that facilitates the root-to-shoot transport of sulfate in the vasculature. In Arabidopsis (Arabidopsis thaliana), SULTR3;5 was colocalized with the SULTR2;1 low-affinity sulfate transporter in xylem parenchyma and pericycle cells in roots. In a yeast (Saccharomyces cerevisiae) expression system, sulfate uptake was hardly detectable with SULTR3;5 expression alone; however, cells coexpressing both SULTR3;5 and SULTR2;1 showed substantial uptake activity that was considerably higher than with SULTR2;1 expression alone. The V(max) value of sulfate uptake activity with SULTR3;5-SULTR2;1 coexpression was approximately 3 times higher than with SULTR2;1 alone. In Arabidopsis, the root-to-shoot transport of sulfate was restricted in the sultr3;5 mutants, under conditions of high SULTR2;1 expression in the roots after sulfur limitation. These results suggested that SULTR3;5 is constitutively expressed in the root vasculature, but its function to reinforce the capacity of the SULTR2;1 low-affinity transporter is only essential when SULTR2;1 mRNA is induced by sulfur limitation. Consequently, coexpression of SULTR3;5 and SULTR2;1 provides maximum capacity of sulfate transport activity, which facilitates retrieval of apoplastic sulfate to the xylem parenchyma cells in the vasculature of Arabidopsis roots and may contribute to the root-to-shoot transport of sulfate.

Anion Transport Proteins↗
PubMed2005

The root tip and accelerating region suppress elongation of the decelerating region without any effects on cell turgor in primary roots of maize under water stress.

To identify the region in which a root perceives a decrease in the ambient water potential and changes its elongation rate, we applied two agar blocks (1 x 1 x 1 mm(3)) with low water potential bilaterally to primary roots of maize (Zea mays) at various positions along the root. When agar blocks with a water potential of -1.60 MPa (-1.60-MPa blocks) or lower were attached to a root tip, the rate of elongation decreased. This decrease did not result from any changes in the water status of elongating cells and was not reversed when the -1.60-MPa blocks were replaced by -0.03-MPa blocks. The rate decreased slightly and was unaffected, respectively, when -1.60-MPa blocks were applied to the so-called decelerating region of the elongating zone and the mature region. However, the rate decreased markedly and did not recover for several hours at least when such blocks were attached to the accelerating region. In this case, the turgor pressure of the elongating cells decreased immediately after the application of the blocks and recovered thereafter. The decrease in elongation rate caused by -1.60-MPa blocks applied to the root tip was unaffected by additional -0.03-MPa blocks applied to the accelerating region and vice versa. We concluded that a significant reduction in root growth could be induced by water stress at the root tip, as well as in the accelerating region of the elongating zone, and that transmission of some signal from these regions to the decelerating region might contribute to the suppression of cell elongation in the elongation region.

Osmotic Pressure↗
PubMed1999

Arabidopsis alcohol dehydrogenase expression in both shoots and roots is conditioned by root growth environment.

It is widely accepted that the Arabidopsis Adh (alcohol dehydrogenase) gene is constitutively expressed at low levels in the roots of young plants grown on agar media, and that the expression level is greatly induced by anoxic or hypoxic stresses. We questioned whether the agar medium itself created an anaerobic environment for the roots upon their growing into the gel. beta-Glucuronidase (GUS) expression driven by the Adh promoter was examined by growing transgenic Arabidopsis plants in different growing systems. Whereas roots grown on horizontal-positioned plates showed high Adh/GUS expression levels, roots from vertical-positioned plates had no Adh/GUS expression. Additional results indicate that growth on vertical plates closely mimics the Adh/GUS expression observed for soil-grown seedlings, and that growth on horizontal plates results in induction of high Adh/GUS expression that is consistent with hypoxic or anoxic conditions within the agar of the root zone. Adh/GUS expression in the shoot apex is also highly induced by root penetration of the agar medium. This induction of Adh/GUS in shoot apex and roots is due, at least in part, to mechanisms involving Ca2+ signal transduction.

Alcohol Dehydrogenase↗
PubMed2004

A nonsymbiotic root hair tip growth phenotype in NORK-mutated legumes: implications for nodulation factor-induced signaling and formation of a multifaceted root hair pocket for bacteria.

The Medicago truncatula Does not Make Infections (DMI2) mutant is mutated in the nodulation receptor-like kinase, NORK. Here, we report that NORK-mutated legumes of three species show an enhanced touch response to experimental handling, which results in a nonsymbiotic root hair phenotype. When care is taken not to induce this response, DMI2 root hairs respond morphologically like the wild type to nodulation factor (NF). Global NF application results in root hair deformation, and NF spot application induces root hair reorientation or branching, depending on the position of application. In the presence of Sinorhizobium meliloti, DMI2 root hairs make two-dimensional 180 degrees curls but do not entrap bacteria in a three-dimensional pocket because curling stops when the root hair tip touches its own shank. Because DMI2 does not express the promoter of M. truncatula Early Nodulin11 (ENOD11) coupled to beta-glucuronidase upon NF application, we propose a split in NF-induced signaling, with one branch to root hair curling and the other to ENOD11 expression.

Genes, Plant↗
PubMed2000

The ROOT MERISTEMLESS1/CADMIUM SENSITIVE2 gene defines a glutathione-dependent pathway involved in initiation and maintenance of cell division during postembryonic root development.

Activation of cell division in the root apical meristem after germination is essential for postembryonic root development. Arabidopsis plants homozygous for a mutation in the ROOT MERISTEMLESS1 (RML1) gene are unable to establish an active postembryonic meristem in the root apex. This mutation abolishes cell division in the root but not in the shoot. We report the molecular cloning of the RML1 gene, which encodes the first enzyme of glutathione (GSH) biosynthesis, gamma-glutamylcysteine synthetase, and which is allelic to CADMIUM SENSITIVE2. The phenotype of the rml1 mutant, which was also evident in the roots of wild-type Arabidopsis and tobacco treated with an inhibitor of GSH biosynthesis, could be relieved by applying GSH to rml1 seedlings. By using a synchronized tobacco cell suspension culture, we showed that the G(1)-to-S phase transition requires an adequate level of GSH. These observations suggest the existence of a GSH-dependent developmental pathway essential for initiation and maintenance of cell division during postembryonic root development.

Alleles↗
PubMed2001

Changes in root cap pH are required for the gravity response of the Arabidopsis root.

Although the columella cells of the root cap have been identified as the site of gravity perception, the cellular events that mediate gravity signaling remain poorly understood. To determine if cytoplasmic and/or wall pH mediates the initial stages of root gravitropism, we combined a novel cell wall pH sensor (a cellulose binding domain peptide-Oregon green conjugate) and a cytoplasmic pH sensor (plants expressing pH-sensitive green fluorescent protein) to monitor pH dynamics throughout the graviresponding Arabidopsis root. The root cap apoplast acidified from pH 5.5 to 4.5 within 2 min of gravistimulation. Concomitantly, cytoplasmic pH increased in columella cells from 7.2 to 7.6 but was unchanged elsewhere in the root. These changes in cap pH preceded detectable tropic growth or growth-related pH changes in the elongation zone cell wall by 10 min. Altering the gravity-related columella cytoplasmic pH shift with caged protons delayed the gravitropic response. Together, these results suggest that alterations in root cap pH likely are involved in the initial events that mediate root gravity perception or signal transduction.

Arabidopsis↗
PubMed2005

The sealing ability of an epoxy resin root canal sealer after Nd:YAG laser irradiation of the root canal.

AIM: To evaluate ex vivo the effect of Nd:YAG laser irradiation with and without black ink on instrumented root canal walls, and the degree of both coronal and apical microleakage of filled root canals. METHODOLOGY: Seventy-two single-rooted teeth were instrumented up to a size 40 K-file, and then divided into six groups of 10 teeth: groups 1 and 4 remained unlased and acted as control groups, groups 2 and 5 were treated with a Nd:YAG laser (Fidelis Plus, Herzele, Belgium), groups 3 and 6 were treated with a laser and black ink; the remaining 12 teeth served as positive and negative controls. The laser was operated at 1.5 W, 15 Hz, four times for 5 s with a 20-s interval. Groups 4-6 were filled using cold lateral condensation of gutta-percha and AH26. After storage in water for 48 h at 37 degrees C, through-and-through leakage (L in microL day-1) was measured for 48 h under a pressure of 1.2 atm using a fluid transport model and recorded as L=0 (L1), 0 10 (L3). After the assessment of leakage with the fluid transport model, the teeth were immersed in rhodamine B solution for 48 h at 37 degrees C. Apical and coronal dye leakage was scored after longitudinal splitting of these teeth. All teeth of groups 1-3 were split longitudinally and observed under SEM for evaluation of remaining smear layer. RESULTS: Through-and-through leakage was only observed in the group lased with black ink (two samples-L2). Apical and coronal dye leakage was observed in all groups; there were no statistically significant differences amongst the three experimental groups. The through-and-through leakage, measured with the fluid transport model in two teeth of group 6, was confirmed in the dye leakage test (rhodamine B dye was observed along the total length of the root filling). There was evidence of melted and ablated root canal dentine in the laser-treated groups. These findings were more obvious in root canals lased in association with black ink. All apical foramina in the lased group remained patent. CONCLUSIONS: Nd:YAG laser irradiation with black ink increased the amount of melted and ablated dentine areas compared with that without black ink. Nd:YAG lasing in association with black ink did not result in a reduction of either coronal or apical microleakage in root filled teeth.

Aluminum Silicates↗
PubMed1989

The pattern of secondary root formation in curving roots of Arabidopsis thaliana (L.) Heynh.

A gravitational stimulus was used to induce the curvature of the main root of Arabidopsis thaliana. The number of secondary roots increased on the convex side and decreased on the concave side of any curved main root axes in comparison with straight roots used as the control. The same phenomenon was observed with the curved main roots of plants grown on a clinostat and of mutant plants exhibiting random root orientation. The data suggest that the pattern of lateral root formation is associated with curvature but is independent of the environmental stimuli used to induce curvature.

Arabidopsis↗
PubMed1989

Respiration rate in maize roots is related to concentration of reduced nitrogen and proliferation of lateral roots.

The relationship between specific rate of respiration (respiration rate per unit root dry weight) and concentration of reduced nitrogen was examined for maize (Zea mays L.) roots. Plants with 2 primary nodal root axes were grown for 8 days in a split-root hydroponic system in which NO3- was supplied to both axes at 1.0 mol m-3, to one axis at 1.0 mol m-3 and the other axis at 0.0 mol m-3, or to both axes at 0.0 mol m-3. Respiration rates and root characteristics were measured at 2-day intervals. Specific rate of respiration was positively correlated in a nonlinear relationship with concentration of reduced nitrogen. The lowest specific rates of respiration occurred when neither axis received exogenous NO3- and the concentration of reduced nitrogen in the axes was less than 9 mg g-1. The greatest rates occurred in axes that were actively absorbing NO3- and contained more than 35 mg g-1 of reduced nitrogen. At 23 mg g-1 of reduced nitrogen, below which initiation of lateral branches was decreased by 30-50%, specific rate of respiration was 17% greater for roots actively absorbing NO3- than for roots not absorbing NO3-. Increases in specific rate of respiration associated with concentrations of reduced nitrogen greater than 23 mg g-1 were concluded to be attributable primarily to proliferation of lateral branches.

Carbon Dioxide↗
PubMed2006

Root aeration in rice (Oryza sativa): evaluation of oxygen, carbon dioxide, and ethylene as possible regulators of root acclimatizations.

Adventitious roots of rice (Oryza sativa) acclimatize to root-zone O(2) deficiency by increasing porosity, and induction of a barrier to radial O(2) loss (ROL) in basal zones, to enhance longitudinal O(2) diffusion towards the root tip. Changes in root-zone gas composition that might induce these acclimatizations, namely low O(2), elevated ethylene, ethylene-low O(2) interactions, and high CO(2), were evaluated in hydroponic experiments. Neither low O(2) (0 or 0.028 mol m(-3) O(2)), ethylene (0.2 or 2.0 microl l(-1)), or combinations of these treatments, induced the barrier to ROL. This lack of induction of the barrier to ROL was despite a positive response of aerenchyma formation to low O(2) and elevated ethylene. Carbon dioxide at 10 kPa had no effect on root porosity, the barrier to ROL, or on growth. Our findings that ethylene does not induce the barrier to ROL in roots of rice, even though it can enhance aerenchyma formation, shows that these two acclimatizations for improved root aeration are differentially regulated.

Acclimatization↗