Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “root”

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 1,765 records · Page 98Linked to original sources
PubMed2004

Phenotypic variation of Pseudomonas brassicacearum as a plant root-colonization strategy.

Pseudomonas brassicacearum was isolated as a major root-colonizing population from Arabidopsis thaliana. The strain NFM421 of P. brassicacearum undergoes phenotypic variation during A. thaliana and Brassica napus root colonization in vitro as well as in soil, resulting in different colony appearance on agar surfaces. Bacteria forming translucent colonies (phase II cells) essentially were localized at the surface of young roots and root tips, whereas wild-type cells (phase I cells) were localized at the basal part of roots. The ability of phase II cells to spread and colonize new sites on root surface correlates with over-production of flagellin as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of surface proteins and microsequencing. Moreover, phase II cells showed a higher ability to swim and to swarm on semisolid agar medium. Phase I and phase II cells of P. brassicacearum NFM421 were tagged genetically with green fluorescent protein and red fluorescent protein. Confocal scanning laser microscopy was used to localize phase II cells on secondary roots and root tips of A. thaliana, whereas phase I cells essentially were localized at the basal part of roots. These experiments were conducted in vitro and in soil. Phenotypic variation on plant roots is likely to be a colonization strategy that may explain the high colonization power of P. brassicacearum.

Arabidopsis↗
PubMed1994

Anatomic and radiographic study of dorsal root ganglia.

Anatomic and radiographic studies were made to investigate normal variation of dorsal root ganglia in lumbosacral roots. The spinal nerves could be divided into two groups, with and without bifurcation of ventral nerve root and dorsal root ganglion. The bifurcated group was further classified into three types. L4 and L5 nerve roots were all bifurcated, and S1 were all nonbifurcated. The positions of dorsal root ganglia were classified into three types: intraspinal, intraforaminal, and extraforaminal. At L4 and L5 nerve roots, they were mostly intraforaminal, whereas at S1, they were mostly intraspinal. Proximally placed ganglia had a high frequency of ganglionic indentation. The incidence of intraspinal dorsal root ganglia was much higher clinically than in anatomic studies. Variations in connecting patterns or positions of dorsal root ganglia may be related to the occurrence and variety of radicular symptoms. The dorsal root ganglia is clinically important, and its location may correspond to clinical symptoms.

Adult↗
PubMed1994

Regional blood flow, plasma volume, and vascular permeability in the spinal cord, the dural sac, and lumbar nerve roots.

OBJECTIVES: This study quantified the regional blood flow (RBF), plasma volume (PV), and the vascular permeability (VP) in the spinal cord, spinal nerve roots, and the dural sac. SUMMARY OF BACKGROUND DATA: Spinal cord hemodynamics have been investigated. However, the full segmental distribution of blood flow to the spinal cord and nerve roots has not been worked out. Vascular permeability of the spinal cord and nerve roots has been investigated but results regarding the spinal nerve roots have not been consistent. METHODS: Eight Labrador dogs were used. Regional blood flow was measured with microspheres. Plasma volume and vascular permeability were assessed by the distribution spaces of radioactively labeled plasma proteins. RESULTS: Regional blood flow was highest in the cervical and lumbar cord. Average (SEM) RBF values of the cord and spinal nerve roots were 10.4 +/- 1.0 and 4.4 +/- 0.5 mL/min 100 g, respectively. Plasma volume of the spinal cord was 0.85 +/- 0.06 mL/100 g and 1.29 +/- 0.17 mL/100 g in the spinal nerve roots. Vessels in the spinal nerve roots had significantly greater permeability to albumin than those of the spinal cord (P < 0.001). CONCLUSIONS: The quantitative flow measurements showed the existence of three main anatomic territories in the cord. The vascular permeability of vessel in the spinal nerve roots appears greater than that of the spinal cord, indicating that spinal nerve roots are located outside the blood brain barrier. Diffusion might be one of the nutritional pathways to spinal nerve roots.

Animals↗
PubMed1998

Symptom provocation of fluoroscopically guided cervical nerve root stimulation. Are dynatomal maps identical to dermatomal maps?

STUDY DESIGN: This prospective study consisted of mechanical stimulation of cervical nerve roots C4 to C8 in patients with cervical radicular symptoms undergoing diagnostic selective nerve root block. OBJECTIVES: To document the distribution of pain and paresthesias that result from stimulation of specific cervical nerve roots and compare that distribution to documented sensory dermatomal maps. SUMMARY OF BACKGROUND DATA: Cervical dermatomes were first studied in the late 19th century. The results of those studies underpin current clinical decision making for patients with neck and arm pain. However, it has been observed that patients with radicular symptoms may have cervical pathology by radiographic imaging that is not corroborative, or have imaging studies that suggest a lesion at a level other than the one suggested by the patient's dermatomal symptoms. These observations may suggest that cervical dermatomal mapping is inaccurate or the distribution of referred symptoms (dynatome) from cervical root irritation is different than the sensory deficit outlined by dermatomal maps. METHODS: Inclusion criteria consisted of consecutive patients undergoing fluoroscopically guided diagnostic cervical selective nerve root blocks from C4 to C8. Immediately preceding contrast injection, mechanical stimulation of the root was performed. An independent observer interviewed and recorded the location of provoked symptoms on a pain diagram. Visual data was subsequently compiled using a 793 body sector bit map. Forty-three clinically relevant body regions were defined on this bit map. Frequencies of symptom provocation and likelihood of symptom location from C4 to C8 stimulation of each nerve root were generated. RESULTS: One hundred thirty-four cervical nerve root stimulations were performed on 87 subjects. There were 4 nerve root stimulations at C4, 14 at C5, 43 at C6, 52 at C7, and 21 at C8. Analyzing the frequency of involvement of the predetermined clinically relevant body regions either individually or in various combinations yielded more than 1,000 bits of data. Although the distribution of symptom provocation resembled the classic dermatomal maps for cervical nerve roots, symptoms were frequently provoked outside of the distribution of classic dermatomal maps. CONCLUSION: The current study demonstrates a distinct difference between dynatomal and dermatomal maps.

Cervical Vertebrae↗
PubMed2002

Intraoperative neurophysiologic detection of iatrogenic C5 nerve root injury during laminectomy for cervical compression myelopathy.

STUDY DESIGN: A retrospective and prospective study was conducted to investigate intraoperative neurophysiologic monitoring during cervical laminectomy to detect iatrogenic C5 nerve root palsy. OBJECTIVE: To evaluate the usefulness of various intraoperative neuromonitoring methods for identifying C5 nerve root palsy. SUMMARY OF BACKGROUND DATA: One unsolved complication after laminectomy or laminoplasty for cervical compression myelopathy is C5 nerve root palsy. It can go undetected even in the presence of intraoperative neuromonitoring with conventional upper extremity mixed nerve or dermatomal somatosensory-evoked potentials or transcranial motor-evoked potentials, recording typically from hand muscles. METHODS: The intraoperative neuromonitoring data of 200 patients who underwent cervical laminectomy for myelopathy between 1998 and 2000 were reviewed for C5 nerve root palsy. Retrospective studies were conducted for the first 132 patients, who were monitored with conventional techniques including ulnar and posterior tibial nerve somatosensory-evoked potentials, C5-C7 dermatomally evoked potentials, and transcranial electrical motor-evoked potentials recorded from hand and leg muscles. Prospective studies then were applied to the remaining 68 patients, for whom transcranial electrical motor-evoked potentials and spontaneous electromyography were monitored from deltoid and biceps muscles in the wake of undetected C5 nerve root palsy from conventional neurophysiologic monitoring methods. RESULTS: In the retrospective cohort, six patients presented after surgery with C5 nerve root palsy showing unilateral deltoid muscle paralysis despite entirely unremarkable conventional somatosensory-evoked potentials, dermatomally evoked potentials, and transcranial electrical motor-evoked potentials from hand and leg muscles. For the prospective cohort, two patients experienced postoperative iatrogenic C5 motor nerve root palsy. Impending C5 nerve root injuries after laminectomy were successfully identified in both patients showing significant changes in deltoid and biceps transcranial electrical motor-evoked potentials and spontaneous electromyography, thereby averting more serious consequence. There were no false-negative and false-positive results. CONCLUSIONS: In an effort to reduce postoperative C5 nerve root palsy, the clinician should consider intraoperative deltoid and biceps transcranial electrical motor-evoked potential and spontaneous electromyography monitoring whenever there is potential for iatrogenic C5 nerve root injury.

Adult↗
PubMed2002

Detection of lumbosacral nerve root compression with a novel composite nerve conduction measurement.

STUDY DESIGN: Multivariate logistic regression techniques were used to develop a composite nerve conduction measurement that detects lumbosacral (L5, S1, or both) nerve root compression. OBJECTIVES: To evaluate the diagnostic efficacy of a composite nerve conduction measurement for detection of lumbosacral nerve root compression. SUMMARY OF BACKGROUND DATA: Nerve root involvement is characterized by clinical abnormalities and confirmed by radiologic and electrodiagnostic studies. Imaging studies visualize structural abnormalities; however, they are associated with high false-positive rates. Electrodiagnostic methods assess the physiologic integrity of the nerve roots. One form of electrodiagnostic testing, nerve conduction studies, is widely used for evaluation of musculoskeletal and neuromuscular complaints. Although similar clinical value is expected for the evaluation of nerve root compromise, prior applications of nerve conduction studies have yielded widely varying results. METHODS: Two groups of subjects were compared. The L5-S1 compression group was composed of 25 patients with magnetic resonance imaging-confirmed lumbosacral (L5, S1, or both) nerve root compression and symptoms in the appropriate segmental distribution. The majority of subjects (22) had at least one of the following findings on physical examination: positive straight-leg raise test, diminished ankle reflexes, sensory loss, or weakness. The control group consisted of 35 asymptomatic individuals with no history of radiculopathy or potentially confounding neuropathology. The posterior tibial and deep peroneal nerves were evaluated bilaterally in all study subjects using standard nerve conduction procedures, which consisted of the measurement of distal motor latencies and F-wave latencies that assess nerve root pathophysiology. A composite nerve conduction measurement was determined using multivariate logistic regression analysis. The efficacy of the composite measurement was assessed by receiver operating characteristic curve analysis and by the diagnostic sensitivity and specificity. RESULTS: Five F-wave latency parameters (peroneal mean F-wave latency, odds ratio = 0.42; peroneal seventh F-wave latency decile, odds ratio = 2.71; tibial mean F-wave latency, odds ratio = 8.90; tibial first F-wave latency decile, odds ratio = 0.47; tibial maximum F-wave latency, odds ratio = 0.44) were found to be predictive of nerve root compression. A composite nerve conduction measurement, NC composite, constructed from these five parameters (NC composite = exp(phi)/(1 + exp(phi)), phi = -31.2 + 1.0 * Per7 Decile - 0.88 * PerMean + 2.2 * TibMean - 0.88 * Tib1 Decile - 0.83 * TibMax) yielded an area under the receiver operating characteristic curve of 0.91. At a threshold of 0.20, NC composite had a diagnostic specificity of 84.3% and a sensitivity of 83.3%. CONCLUSION: This preliminary study suggests that a novel composite nerve conduction measurement, based on F-wave latency parameters, may be highly effective at detecting magnetic resonance imaging-confirmed lumbosacral nerve root compression. Because these measurements provide objective evidence of functional nerve root compromise and are noninvasive, they may be of diagnostic value to clinicians evaluating patients presenting with low back and leg pain.

Adult↗
PubMed2002

Changes in the microhemodynamics of nerve root retraction in patients with lumbar spinal canal stenosis.

STUDY DESIGN: Assessment of qualitative and quantitative changes in the microcirculation of nerve roots, such as the diameter of blood vessels and the low rate of erythrocytes, was observed during lumbar interbody fusion. OBJECTIVE: To ascertain changes in the microcirculation of nerve roots before and after retraction during lumbar interbody fusion surgery. SUMMARY OF BACKGROUND DATA: The changes in microhemodynamics caused by nerve root retraction have not yet been elucidated. METHODS: Subjects were patients with lumbar spinal canal stenosis who underwent lumbar interbody fusion. Changes in the microcirculation of nerve roots were examined in the L5 nerve root in 26 patients and the S1 nerve root in 3 patients. Through the use of video images captured by contact endoscope and stored in a computer, erythrocytes were automatically followed to measure flow rate and the diameter of blood vessels. RESULTS: Plasma skimming, where blood cells and plasma flow separately, was seen in 3 of the 29 patients (10.3%) before retraction of the nerve root and in 8 of the 29 patients (27.6%) following retraction. Intravascular erythrocyte agglutination, when erythrocytes flow in clumps due to changes in the charge state of erythrocytes, was seen in blood vessels larger than 100 microm in 3 patients (10.3%) after retraction. Following nerve root retraction, the flow rate of erythrocytes through blood vessels decreased an average of 23.9% (P< 0.005). CONCLUSIONS: A contact endoscope was used to observe the microhemodynamics of nerve roots before and after retraction of the nerve root during lumbar interbody fusion surgery, and a decrease in the flow rate of erythrocytes was observed.

Adult↗
PubMed2003

Palsy of the C5 nerve root after midsagittal-splitting laminoplasty of the cervical spine.

STUDY DESIGN: The imaging characteristics of postoperative C5 nerve root palsy after midsagittal-splitting laminoplasty for cervical myelopathy, including those observed on plain radiography, computed tomography, and magnetic resonance imaging, were analyzed. OBJECTIVE: To investigate the imaging findings that predict occurrence of C5 nerve root palsy after midsagittal-splitting laminoplasty. SUMMARY OF BACKGROUND DATA: There have been several reports on imaging findings for postoperative nerve root palsy after open-door laminoplasty. However, there have been no detailed reports on imaging characteristics that predict the occurrence of nerve root palsy after midsagittal-splitting laminoplasty. METHODS: The study included 45 consecutive patients undergoing midsagittal-splitting laminoplasty with sufficient pre- and postoperative imaging examinations: 27 patients with cervical spondylotic myelopathy (CSM), 14 patients with ossification of the posterior longitudinal ligament (OPLL), and 4 patients with cervical disc herniation. Characteristics of pre- and postoperative plain radiographs, computed tomography scans, and magnetic resonance images were compared between the patients with and those without C5 nerve root palsy. RESULTS: Palsy of the C5 nerve root developed in 4 patients, and did not develop in 41 patients. Of the four patients with C5 nerve root palsy, one had CSM and the other three had OPLL. The incidence of C5 nerve root palsy involved 3 of 14 patients with OPLL patients (21.4%) and 1 of 31 patients without OPLL (3.2%) (P = 0.08). For both diseases, the patients with palsy tended to have increased postoperative cervical lordosis (P = 0.21). As for anterior compression on the spinal cord at C3, the P value for the comparison between the group with and the group without palsy was 0.07 for preoperative compression and 0.01 for postoperative compression. CONCLUSIONS: The preliminary data suggest that patients who have OPLL with marked anterior compression on spinal cord at C3 can be at risk for postoperative C5 nerve root palsy after midsagittal-splitting laminoplasty. Also, a postoperative increase in cervical lordosis may be the cause of postoperative nerve root palsy.

Adult↗
PubMed2005

Lumbar nerve root palsy after adult spinal deformity surgery.

STUDY DESIGN: A retrospective study was conducted to investigate the incidence and prognosis of postoperative lumbar nerve root palsy after surgical treatment for adult spinal deformity. OBJECTIVE: To decipher the incidence of postoperative lumbar nerve root palsy and recovery in 361 adult spinal deformity patients who underwent 407 spinal fusion surgeries. SUMMARY OF BACKGROUND DATA: Although lumbar nerve root palsy is a known complication of spinal surgery, there are no large studies that have examined its incidence or prognosis. METHODS: Three hundred and sixty-one consecutive patients who underwent 407 procedures for adult deformity spinal surgery were reviewed. Patients in this study did not have spinal cord injury or nerve root compression on the postoperative imaging study (obtained for change in neurologic examination). The incidence of nerve root palsy was based on postoperative muscle strength, which was followed for a minimum of 3 and an average of 7 years. RESULTS: The overall incidence of lumbar nerve root palsy was 2.9% with a 1.4% incidence in primary and 3.8% incidence in revision surgery. The incidence was 0.9, 1.5, and 7.4% for fusion of <5 levels, 5 to 10 levels, and >10 levels, respectively. The incidence of nerve root palsy for posterior only, same day anterior-posterior, and staged posterior was 1.3, 3, and 7.2%, respectively. While L5 was the most commonly injured nerve root, all other lumbar nerve roots were also involved. There were no S1 injuries. Although there was some recovery in most injuries, Grade IV injuries had the best recovery at 1-year follow-up. CONCLUSION: Patients with increasingly complex spinal deformities are at a higher risk for postoperative lumbar nerve root palsy. These injuries can be treated nonoperatively when there is no identifiable cause on postoperative imaging studies.

Adult↗
PubMed2006

Continuous EMG recordings and intraoperative electrical stimulation for identification and protection of cervical nerve roots during foraminal tumor surgery.

OBJECTIVE: Spinal cord function is now routinely monitored with somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) during surgery for intraspinal cervical dumbbell and foraminal tumors. However, upper extremity nerve roots are also at risk during these procedures. Anatomic relations are frequently difficult to interpret because the nerve roots may be displaced by the tumor. We used electrical stimulation with compound muscle action potential (CMAP) recordings at multiple sites to identify the location and course of the involved nerve root and to provide real-time information regarding the functional status of the roots to predict postoperative outcome. METHODS: Ten patients were monitored during surgery for cervical dumbbell or foraminal tumors. SEPs and MEPs were monitored as a routine procedure. CMAPs were recorded from needle electrodes placed in the deltoid, biceps, triceps, and flexor carpi ulnaris muscles. Spontaneous electromyography (EMG) muscle activity was also continuously monitored. A handheld monopolar stimulation electrode was used to elicit evoked EMG responses to identify and trace the course of nerves in relation to the tumor. In four patients, the stimulation threshold was tested before and after tumor resection to predict postoperative nerve root function. RESULTS: Electrical stimulation with CMAP recording was successful in localizing nerve roots during tumor resection in all 10 patients. Monitoring predicted postoperative nerve root preservation after tumor removal in each case. It was possible to identify either by using low-level stimulation (<2.0 V) or by observing changes in spontaneous EMG amplitude if activation was present during surgical dissection. The monitoring of spontaneous muscle activity in response to direct or indirect surgical manipulation during tumor resection also provided continuous assessment of nerve root function and identified any physiologic disturbance induced by surgical manipulation. CONCLUSIONS: Electrical stimulation in the operating field and recording of CMAPs facilitated nerve root identification and predicted postoperative function during dissection and separation from ligamentous or neoplastic tissue in 10 patients. Electrical stimulation might also be useful to predict postoperative preservation of function when nerve root sacrifice is necessary and no motor response is detected intraoperatively.

Action Potentials↗
PubMed2002

SOS4, a pyridoxal kinase gene, is required for root hair development in Arabidopsis.

Root hair development in plants is controlled by many genetic, hormonal, and environmental factors. A number of genes have been shown to be important for root hair formation. Arabidopsis salt overly sensitive 4 mutants were originally identified by screening for NaCl-hypersensitive growth. The SOS4 (Salt Overly Sensitive 4) gene was recently isolated by map-based cloning and shown to encode a pyridoxal (PL) kinase involved in the production of PL-5-phosphate, which is an important cofactor for various enzymes and a ligand for certain ion transporters. The root growth of sos4 mutants is slower than that of the wild type. Microscopic observations revealed that sos4 mutants do not have root hairs in the maturation zone. The sos4 mutations block the initiation of most root hairs, and impair the tip growth of those that are initiated. The root hairless phenotype of sos4 mutants was complemented by the wild-type SOS4 gene. SOS4 promoter-beta-glucuronidase analysis showed that SOS4 is expressed in the root hair and other hair-like structures. Consistent with SOS4 function as a PL kinase, in vitro application of pyridoxine and pyridoxamine, but not PL, partially rescued the root hair defect in sos4 mutants. 1-Aminocyclopropane-1-carboxylic acid and 2,4-dichlorophenoxyacetic acid treatments promoted root hair formation in both wild-type and sos4 plants, indicating that genetically SOS4 functions upstream of ethylene and auxin in root hair development. The possible role of SOS4 in ethylene and auxin biosynthesis is discussed.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2002

ACTIN2 is essential for bulge site selection and tip growth during root hair development of Arabidopsis.

Root hairs develop as long extensions from root epidermal cells. After the formation of an initial bulge at the distal end of the epidermal cell, the root hair structure elongates by tip growth. Because root hairs are not surrounded by other cells, root hair formation provides an excellent system for studying the highly complex process of plant cell growth. Pharmacological experiments with actin filament-interfering drugs have provided evidence that the actin cytoskeleton is an important factor in the establishment of cell polarity and in the maintenance of the tip growth machinery at the apex of the growing root hair. However, there has been no genetic evidence to directly support this assumption. We have isolated an Arabidopsis mutant, deformed root hairs 1 (der1), that is impaired in root hair development. The DER1 locus was cloned by map-based cloning and encodes ACTIN2 (ACT2), a major actin of the vegetative tissue. The three der1 alleles develop the mutant phenotype to different degrees and are all missense mutations, thus providing the means to study the effect of partially functional ACT2. The detailed characterization of the der1 phenotypes revealed that ACT2 is not only involved in root hair tip growth, but is also required for correct selection of the bulge site on the epidermal cell. Thus, the der1 mutants are useful tools to better understand the function of the actin cytoskeleton in the process of root hair formation.

Actins↗
PubMed2003

Phytochromes A and B mediate red-light-induced positive phototropism in roots.

The interaction of tropisms is important in determining the final growth form of the plant body. In roots, gravitropism is the predominant tropistic response, but phototropism also plays a role in the oriented growth of roots in flowering plants. In blue or white light, roots exhibit negative phototropism that is mediated by the phototropin family of photoreceptors. In contrast, red light induces a positive phototropism in Arabidopsis roots. Because this red-light-induced response is weak relative to both gravitropism and negative phototropism, we used a novel device to study phototropism without the complications of a counteracting gravitational stimulus. This device is based on a computer-controlled system using real-time image analysis of root growth and a feedback-regulated rotatable stage. Our data show that this system is useful to study root phototropism in response to red light, because in wild-type roots, the maximal curvature detected with this apparatus is 30 degrees to 40 degrees, compared with 5 degrees to 10 degrees without the feedback system. In positive root phototropism, sensing of red light occurs in the root itself and is not dependent on shoot-derived signals resulting from light perception. Phytochrome (Phy)A and phyB were severely impaired in red-light-induced phototropism, whereas the phyD and phyE mutants were normal in this response. Thus, PHYA and PHYB play a key role in mediating red-light-dependent positive phototropism in roots. Although phytochrome has been shown to mediate phototropism in some lower plant groups, this is one of the few reports indicating a phytochrome-dependent phototropism in flowering plants.

Apoproteins↗
PubMed2003

Ethylene modulates root-wave responses in Arabidopsis.

When stimulated to bend downward by being held at 45 degrees off vertical but unable to penetrate into agar-based media, Arabidopsis roots develop waving and looping growth patterns. Here, we demonstrate that ethylene modulates these responses. We determined that agar-containing plates sealed with low-porosity film generate abiotic ethylene concentrations of 0.1 to 0.3 microL L(-1), whereas in plates wrapped with porous tape, ethylene remains at trace levels. We demonstrate that exogenous ethylene at concentrations as low as a few nanoliters per liter modulates root waving, root growth direction, and looping but through partly different mechanisms. Nutrients and Suc modify the effects of ethylene on root waving. Thus, ethylene had little effect on temporal wave frequency when nutrients were omitted but reduced it significantly on nutrient-supplemented agar. Suc masked the ethylene response. Ethylene consistently suppressed the normal tendency for roots of Landsberg erecta to skew to the right as they grow against hard-agar surfaces and also generated righthanded petiole twisting. Furthermore, ethylene suppressed root looping, a gravity-dependent growth response that was enhanced by high nutrient and Suc availability. Our work demonstrates that cell file twisting is not essential for root waving or skewing to occur. Differential flank growth accounted for both the extreme root waving on zero-nutrient plates and for root skewing. Root twisting was nutrient-dependent and was thus strongly associated with the looping response. The possible role of auxin transport in these responses and the involvement of circadian rhythms are discussed.

Arabidopsis↗
PubMed2004

Microarray analyses of gene expression during adventitious root development in Pinus contorta.

In order to investigate the gene expression pattern during adventitious root development, RNA of Pinus contorta hypocotyls, pulse-treated with the auxin indole-3-butyric acid and harvested at distinct developmental time points of root development, was hybridized to microarrays containing 2,178 cDNAs from Pinus taeda. Over the period of observation of root development, the transcript levels of 220 genes changed significantly. During the root initiation phase, genes involved in cell replication and cell wall weakening and a transcript encoding a PINHEAD/ZWILLE-like protein were up-regulated, while genes related to auxin transport, photosynthesis, and cell wall synthesis were down-regulated. In addition, there were changes in transcript abundance of genes related to water stress. During the root meristem formation phase the transcript abundances of genes involved in auxin transport, auxin responsive transcription, and cell wall synthesis, and of a gene encoding a B-box zinc finger-like protein, increased, while those encoding proteins involved in cell wall weakening decreased. Changes of transcript abundance of genes related to water stress during the root meristem formation and root formation phase indicate that the plant roots had become functional in water transport. Simultaneously, genes involved in auxin transport were up-regulated, while genes related to cell wall modification were down-regulated. Finally, during the root elongation phase down-regulation of transcripts encoding proteins involved in cell replication and stress occurred. Based on the observed changes in transcript abundances, we suggest hypotheses about the relative importance of various physiological processes during the auxin-induced development of roots in P. contorta.

Cell Division↗
PubMed2004

Aluminum resistance in maize cannot be solely explained by root organic acid exudation. A comparative physiological study.

Root apical aluminum (Al) exclusion via Al-activated root citrate exudation is widely accepted as the main Al-resistance mechanism operating in maize (Zea mays) roots. Nonetheless, the correlation between Al resistance and this Al-exclusion mechanism has not been tested beyond a very small number of Al-resistant and Al-sensitive maize lines. In this study, we conducted a comparative study of the physiology of Al resistance using six different maize genotypes that capture the range of maize Al resistance and differ significantly in their genetic background (three Brazilian and three North American genotypes). In these maize lines, we were able to establish a clear correlation between root tip Al exclusion (based on root Al content) and Al resistance. Both Al-resistant genotypes and three of the four Al-sensitive lines exhibited a significant Al-activated citrate exudation, with no evidence for Al activation of root malate or phosphate release. There was a lack of correlation between differential Al resistance and root citrate exudation for the six maize genotypes; in fact, one of the Al-sensitive lines, Mo17, had the largest Al-activated citrate exudation of all of the maize lines. Our results indicate that although root organic acid release may play a role in maize Al resistance, it is clearly not the only or the main resistance mechanism operating in these maize roots. A number of other potential Al-resistance mechanisms were investigated, including release of other Al-chelating ligands, Al-induced alkalinization of rhizosphere pH, changes in internal levels of Al-chelating compounds in the root, and Al translocation to the shoot. However, we were unsuccessful in identifying additional Al-resistance mechanisms in maize. It is likely that a purely physiological approach may not be sufficient to identify these novel Al-resistance mechanisms in maize and this will require an interdisciplinary approach integrating genetic, molecular, and physiological investigations.

Aluminum↗
PubMed2005

The rib1 mutant of Arabidopsis has alterations in indole-3-butyric acid transport, hypocotyl elongation, and root architecture.

Polar transport of the auxin indole-3-butyric acid (IBA) has recently been shown to occur in Arabidopsis (Arabidopis thaliana) seedlings, yet the physiological importance of this process has yet to be fully resolved. Here we describe the first demonstration of altered IBA transport in an Arabidopsis mutant, and show that the resistant to IBA (rib1) mutation results in alterations in growth, development, and response to exogenous auxin consistent with an important physiological role for IBA transport. Both hypocotyl and root IBA basipetal transport are decreased in rib1 and root acropetal IBA transport is increased. While indole-3-acetic acid (IAA) transport levels are not different in rib1 compared to wild type, root acropetal IAA transport is insensitive to the IAA efflux inhibitor naphthylphthalamic acid in rib1, as is the dependent physiological process of lateral root formation. These observed changes in IBA transport are accompanied by altered rib1 phenotypes. Previously, rib1 roots were shown to be less sensitive to growth inhibition by IBA, but to have a wild-type response to IAA in root elongation. rib1 is also less sensitive to IBA in stimulation of lateral root formation and in hypocotyl elongation under most, but not all, light and sucrose conditions. rib1 has wild-type responses to IAA, except under one set of conditions, low light and 1.5% sucrose, in which both hypocotyl elongation and lateral root formation show altered IAA response. Taken together, our results support a model in which endogenous IBA influences wild-type seedling morphology. Modifications in IBA distribution in seedlings affect hypocotyl and root elongation, as well as lateral root formation.

Arabidopsis↗
PubMed2005

Progressive inhibition by water deficit of cell wall extensibility and growth along the elongation zone of maize roots is related to increased lignin metabolism and progressive stelar accumulation of wall phenolics.

Water deficit caused by addition of polyethylene glycol 6000 at -0.5 MPa water potential to well-aerated nutrient solution for 48 h inhibited the elongation of maize (Zea mays) seedling primary roots. Segmental growth rates in the root elongation zone were maintained 0 to 3 mm behind the tip, but in comparison with well-watered control roots, progressive growth inhibition was initiated by water deficit as expanding cells crossed the region 3 to 9 mm behind the tip. The mechanical extensibility of the cell walls was also progressively inhibited. We investigated the possible involvement in root growth inhibition by water deficit of alterations in metabolism and accumulation of wall-linked phenolic substances. Water deficit increased expression in the root elongation zone of transcripts of two genes involved in lignin biosynthesis, cinnamoyl-CoA reductase 1 and 2, after only 1 h, i.e. before decreases in wall extensibility. Further increases in transcript expression and increased lignin staining were detected after 48 h. Progressive stress-induced increases in wall-linked phenolics at 3 to 6 and 6 to 9 mm behind the root tip were detected by comparing Fourier transform infrared spectra and UV-fluorescence images of isolated cell walls from water deficit and control roots. Increased UV fluorescence and lignin staining colocated to vascular tissues in the stele. Longitudinal bisection of the elongation zone resulted in inward curvature, suggesting that inner, stelar tissues were also rate limiting for root growth. We suggest that spatially localized changes in wall-phenolic metabolism are involved in the progressive inhibition of wall extensibility and root growth and may facilitate root acclimation to drying environments.

Blotting, Northern↗