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At least 955 records · Page 53Linked to original sources
PubMed2006

Development of a 9600-clone procedure for oligonucleotide fingerprinting of rRNA genes: utilization to identify soil bacterial rRNA genes that correlate in abundance with the development of avocado root rot.

Oligonucleotide fingerprinting of rRNA genes (OFRG) is an array-based method that generates microbial community profiles through analysis of rRNA gene clone libraries. The original OFRG method allowed 1536 clones to be analyzed per experiment. This report describes a procedure for analyzing 9600 clones per experiment, including a new probe set for bacterial analysis, and improved data processing and statistical analysis tools. The software tools are available at the OFRG website (). Use of the 9600-clone procedure was demonstrated by examining the bacterial rRNA gene compositions of soils subjected to various temperature treatments. These treatments produced a series of soils with a range of abilities to suppress avocado root rot, enabling the identification of bacterial rRNA genes that correlate in abundance with root rot suppressiveness. OFRG analysis of these soils produced 8876 bacterial rRNA gene fingerprints grouped into 5123 clusters, or operational taxonomic units (OTUs). Eleven OTUs exhibited a positive correlation between the number of clones and the percentage of healthy roots. An in silico analysis was performed to examine the relationship between the number of rRNA genes analyzed and the number of correlates (rRNA gene-avocado root rot symptoms) identified. As the number of clones decreased, fewer correlates were identified. To further increase the throughput of the OFRG method, use of a glass slide-fluorescent probe microarray format was also explored.

DNA Fingerprinting↗
PubMed2000

A universal system for the transport of redox proteins: early roots and latest developments.

The transport of proteins binding redox cofactors across a biological membrane is complicated by the fact that insertion of the redox cofactor is often a cytoplasmic process. These cytoplasmically assembled redox proteins must thus be transported in partially or completely folded form. The need for a special transport system for redox proteins was first recognized for periplasmic hydrogenases in gram-negative bacteria. These enzymes, which catalyze the reaction H2 <--> 2H+ + 2e, are composed of a large and a small subunit. Only the small subunit has an unusually long signal sequence of 30-50 amino acid residues, characterized by a conserved motif (S/T)-R-R-x-F-L-K at the N-terminus. This sequence directs export of the large and small subunit complex to the periplasm. Sequencing of microbial genes and genomes has shown that signal sequences with this conserved motif, now referred to as twin-arginine leaders, occur ubiquitously and export different classes of redox proteins, containing iron sulfur clusters, molybdopterin cofactors, polynuclear copper sites or flavin adenine dinucleotide. Mutations in an Escherichia coli operon referred to as mtt (membrane targeting and translocation) or tat (twin arginine translocation) are pleiotropic, i.e. these prevent the expression of a variety of periplasmic oxido-reductases in functional form. The Mtt or Tat pathway is distinct from the well-known Sec pathway and occurs ubiquitously in prokaryotes. The fact that its component proteins share sequence homology with proteins of the delta pH pathway for protein transport associated with chloroplast thylakoid assembly, illustrates the universal nature of this novel protein translocation system.

Amino Acid Sequence↗
PubMed2000

Development of the root pole and cell patterning in Arabidopsis roots.

The root forms at the basal end of an axis that is set up early in embryogenesis, and recent genetic analysis has indicated that auxin transport is required for the formation of the root pole. Drug studies show that auxin transport is also required for the maintenance of the tissue organisation in the seedling root. These studies support existing models for tissue patterning that involve canalised auxin flow. Molecular insights into the mechanism of cell-type specification and patterning has come from the epidermis where positionally controlled cell specification is regulated by a cascade of transcription factors.

Arabidopsis↗
PubMed1999

Changes in hormonal balance and meristematic activity in primary root tips on the slowly rotating clinostat and their effect on the development of the rapeseed root system.

The morphometry of the root system, the meristematic activity and the level of indole-3-acetic acid (IAA), abscisic acid (ABA) and zeatin in the primary root tips of rapeseed seedlings were analyzed as functions of time on a slowly rotating clinostat (1 rpm) or in the vertical controls (1 rpm). The fresh weight of the root system was 30% higher throughout the growth period (25 days) in clinorotated seedlings. Morphometric analysis showed that the increase in biomass on the clinostat was due to greater primary root growth, earlier initiation and greater elongation of the secondary roots, which could be observed even in 5-day-old seedlings. However, after 15 days, the growth of the primary root slowed on the clinostat, whereas secondary roots still grew faster in clinorotated plants than in the controls. At this time, the secondary roots began to be initiated closer to the root tip on the clinostat than in the control. Analysis of the meristematic activity and determination of the levels in IAA, ABA and zeatin in the primary root tips demonstrated that after 5 days on the clinostat, the increased length of the primary root could be the consequence of higher meristematic activity and coincided with an increase in both IAA and ABA concentrations. After 15 days on the clinostat, a marked increase in IAA, ABA and zeatin, which probably reached supraoptimal levels, seems to cause a progressive disturbance of the meristematic cells, during a decrease of primary root growth between 15 and 25 days. These modifications in the hormonal balance and the perturbation of the meristematic activity on the clinostat were followed by a loss of apical dominance, which was responsible for the early initiation of secondary roots, the greater elongation of the root system and the emergence of the lateral roots near the tip of the primary root.

Abscisic Acid↗
PubMed1995

Symbiotic induction of a MADS-box gene during development of alfalfa root nodules.

In response to infection by Rhizobium, highly differentiated organs called nodules form on legume roots. Within these organs, the symbiotic association between the host plant and bacteria is established. A putative plant transcription factor, NMH7, has been identified in alfalfa root nodules. nmh7 contains a MADS-box DNA-binding region and shows homology to flower homeotic genes. This gene is a member of a multigene family in alfalfa and was identified on the basis of nucleic acid homology to plant regulatory protein genes (MADS-box-containing genes) from Antirrhinum and Arabidopsis. RNA analysis and in situ hybridization showed that expression of this class of regulatory genes is limited to the infected cells of alfalfa root nodules and is likely to be involved in the signal transduction pathway initiated by the bacterial symbiont, Rhizobium meliloti. The expression of nmh7 in a root-derived organ is unusual for this class of regulatory genes.

Amino Acid Sequence↗
PubMed1995

Rhizobial lipo-oligosaccharide nodulation factors: multidimensional chromatographic analysis of symbiotic signals involved in the development of legume root nodules.

Nod factors are a group of biologically active oligosaccharide signals that are secreted by symbiotically competent bacteria of the family Rhizobiaceae. Their biosynthesis is determined by rhizobial nodulation (nod) genes, and is specifically induced in response to flavonoids secreted from the roots of host leguminous plants. The biological activity of Nod factors on these host legumes dramatically mimics the early developmental symptoms of the Rhizobium-legume symbiosis including, amongst other effects, root hair deformations and nodule initiation. Structurally, all Nod factors are short oligomers of beta-1,4-linked N-acetylglucosamine residues [usually degree of polymerization (dp) 4 or 5] that are N-acylated on the distal glucosamine. This common 'core' structure may be modified by a number of species-specific substituents on the distal or reducing sugars. These modifications are governed by rhizobial host specificity nod genes. The biological activity of purified Nod factors mirrors this host specificity, indicating that the symbiotic host range of individual Rhizobium species is, at least partially, determined by the variety of Nod factors they are able to produce. Here we describe techniques that are universally applicable to the extraction, chromatographic separation and identification of Nod factors. We have applied these techniques to Nod factors from the broad-host-range species Rhizobium fredii USDA257 and Rhizobium spp. NGR234, and the more narrow-host-range Bradyrhizobium japonicum USDA110, and have identified a group of novel, relatively hydrophilic Nod factors from the NGR234 species that may have implications for Nod factor biosynthesis.

Antigens, Bacterial↗
PubMed1994

Effects of flooding on leaf dynamics and other seedling responses in flood-tolerant Alnus japonica and flood-intolerant Betula platyphylla var. japonica.

Two-year-old seedlings of Alnus japonica Steud. and Betula platyphylla var. japonica Hara were flooded from mid-June to early November, to study the effects of flooding on seedling survival and growth, morphological changes in stems and roots, leaf emergence, leaf fall, and leaf longevity. In A. japonica, growth was not affected by flooding, except for a slight decrease in height growth, but some morphological changes of stems and roots were observed, i.e., stem base hypertrophy, hypertrophied lenticels, formation of adventitious roots and development of new roots. In B. platyphylla var. japonica, growth was severely reduced by flooding and all seedlings died by the 20th week of flooding, without showing any adaptive morphological changes in stems or roots. Flooding induced rapid depression of leaf emergence, promoted leaf abscission, and reduced leaf longevity in B. platyphylla var. japonica. In contrast, in A. japonica, basal leaf senescence was delayed in flooded seedlings, thereby extending leaf longevity compared with unflooded seedlings.

Journal Article↗
PubMed1984

A grass roots approach to developing inpatient nursing unit work groups.

The change has taken three years. Many obstacles (attitudes, scheduling, philosophical differences, etc.) had to be overcome. The unit needed to develop its own autonomy and culture. The head nurse found it necessary to relinquish some control and the clinical nurses, in turn, had to determine manageable versus unmanageable problems. Risks were involved on every level from clinical nurses to the Director of Neuroscience Nursing, but all responded with trust and commitment to nursing and to the organizational goals. The unit was fortunate in a number of ways during the implementation of the work groups. It was advantageous to have a consultant who continually made the head nurse and group leaders look at the unit as a part of a total organization. The many "buts" that were interjected when comparing/contrasting nursing with other professions were refuted. It became apparent that the majority of nurses were fully aware that the profession involves working 24 hours a day, seven days a week including holidays. For the most part, the new graduate understands that hands on care includes such tasks as changing incontinent patients, making beds, and lifting and turning patients. Nursing also means intangible rewards in serving patients who need care. For nurses on our unit, what needed to be changed was the idea that a nurse has little or no control over the work life on a unit. If indeed nurses are committed to nursing, it is up to them, with appropriate support, to identify and alter the aspects of the job which are unsatisfactory.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1997

Wound-Induced Changes of Membrane Voltage, Endogenous Currents, and Ion Fluxes in Primary Roots of Maize.

The effects of mechanical wounding on membrane voltage, endogenous ion currents, and ion fluxes were investigated in primary roots of maize (Zea mays) using intracellular microelectrodes, a vibrating probe, and ion-selective electrodes. After a wedge-shaped wound was cut into the proximal elongation zone of the roots, a large inward current of approximately 60 [mu]A cm-2 was measured, together with a change in the current pattern along the root. The changes of the endogenous ion current were accompanied by depolarization of the membrane voltage of cortex cells up to 5 mm from the wound. Neither inhibitors of ion channels nor low temperature affected the large, wound-induced inward current. The fluxes of H+, K+, Ca2+, and Cl- contributed only about 7 [mu]A cm-2 to the wound-induced ion current. This suggests the occurrence of a large mass flow of negatively charged molecules, such as proteins, sulfated polysaccharides, and galacturonic acids, from the wound. Natural wounding of the root cortex by developing lateral roots caused an outwardly directed current, which was clearly different in magnitude and direction from the current induced by mechanical injury.

Journal Article↗
PubMed1968

Relationships between the development of adventitious roots and the biosynthesis of anthocyanins in first internodes of sorghum.

The initiation and subsequent growth of adventitious roots in excised first internodes of Sorghum vulgare var. Wheatland milo were studied to determine the effect of these processes on anthocyanin biosyntheses. Segmentation of the internodes inhibited both adventitious root growth and accumulation of cyanidin equally in all segments; these results can be interpreted as a common requirement for bidirectional longitudinal transport. The presence of the coleoptile, especially in the absence of the base of the internode, inhibited the growth of the roots, but increased the number of root initials. High intensities of white and blue light which induced cyanidin synthesis slightly decreased adventitious root growth. Anaerobic conditions produced by solution infiltration strongly inhibited the growth of adventitious roots and greatly increased the accumulation of apigeninidin and luteolinidin. Addition of indoleacetic acid, kinetin and cofactors such as pyridoxine produced effects on the initiation and subsequent growth of these roots similar to those effects reported in the literature. But unlike root formation in hypocotyls, the initiation of adventitious roots in Sorghum internodes was not always directly correlated with the accumulation of anthocyanins, and the subsequent growth of these roots was frequently inversely correlated with some of the anthocyanin biosyntheses. The possible nature of these correlations is discussed. Comparisons are made with related Sorghum lines and mutants.

Journal Article↗
PubMed2006

AXR4 is required for localization of the auxin influx facilitator AUX1.

The AUX1 and PIN auxin influx and efflux facilitators are key regulators of root growth and development. For root gravitropism to occur, AUX1 and PIN2 must transport auxin via the lateral root cap to elongating epidermal cells. Genetic studies suggest that AXR4 functions in the same pathway as AUX1. Here we show that AXR4 is a previously unidentified accessory protein of the endoplasmic reticulum (ER) that regulates localization of AUX1 but not of PIN proteins. Loss of AXR4 resulted in abnormal accumulation of AUX1 in the ER of epidermal cells, indicating that the axr4 agravitropic phenotype is caused by defective AUX1 trafficking in the root epidermis.

2,4-Dichlorophenoxyacetic Acid↗