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PubMed2004

Developmental anatomy of the fifth shoot-borne root in young sporophytes of Ceratopteris richardii.

Young sporophytes of the homosporous fern Ceratopteris richardii produce a single shoot-borne root below each leaf. The developmental anatomy of the fifth sporophyte root is described using scanning electron microscopy and histological techniques. Three merophyte orthostichies in the body of the root originate from three proximal division faces of a tetrahedral root apical cell. Eight or nine divisions occur in a relatively regular sequence within each merophyte and produce a characteristic radial anatomical pattern in the root. The exact number of early divisions within a merophyte depends on the merophyte's position within the root as a whole. Predictable inter-merophyte differences arise because a 2-fold (diarch) anatomical symmetry that is characteristic of mature roots is superimposed on a 3-fold radial symmetry that originates behind the apical cell. Before early formative divisions within a merophyte are completed, additional proliferative divisions begin to increase the number of cells within previously established tissue zones. The cellular parameters of early fifth root development in C. richardii are relatively invariant, and are reminiscent of patterns previously described for the heterosporous fern Azolla. Young sporophytes of C. richardii provide a useful model to further investigate the genetic regulation of root development in a non-seed plant, where the anatomy of meristem organization differs from that seen in flowering plant species.

Arabidopsis↗
PubMed1997

The Arabidopsis HY5 gene encodes a bZIP protein that regulates stimulus-induced development of root and hypocotyl.

Plant developmental processes are controlled by both endogenous programs and environmental stimuli. As a photomorphogenetic mutant, hy5 of Arabidopsis has been isolated and characterized. Our detailed characterization has revealed that the mutant is deficient in a variety of stimulus responses, including gravitropic response and waving growth of roots, as well as light-dependent hypocotyl elongation. In the roots and hypocotyl, the hy5 mutation also affects greening and specific cell proliferation such as lateral root formation and secondary thickening. Those phenotypes indicate that the HY5 gene is responsible for the regulation of fundamental developmental processes of the plant cell: cell elongation, cell proliferation, and chloroplast development. Molecular cloning of the HY5 gene using a T-DNA-tagged mutant has revealed that the gene encodes a protein with a bZIP motif, one of the motifs found in transcriptional regulators. Nuclear localization of the HY5 protein strongly suggests that the HY5 gene modulates the signal transduction pathways under the HY5-related development by controlling expression of genes downstream of these pathways.

Amino Acid Sequence↗
PubMed1991

Dependency of Iron Reduction on Development of a Unique Root Morphology in Ficus benjamina L.

The activity of the Fe(3+) reductase of excised adventitious roots of Ficus benjamina L., grown in hydroponic culture without iron, was determined by a colorometric assay simplified by the use of a microplate reader. Reductase activity remained the same from pH 4.5 to 6.5 and decreased sharply above pH 6.5. Acetate buffer inhibited reduction. During early stages of root growth, excised roots did not exhibit Fe(3+) reductase activity. After several weeks and extensive root system development, Fe(3+) reduction still was not detectable in primary roots, but intermediate and high rates of reduction occurred in lateral and newly formed root clusters, respectively. Clustered roots only developed on plants grown at 0 or very low (<1 micromolar) iron. Microscopic examination revealed the root cluster to be composed of up to 30 lateral roots, usually less than 1 millimeter in diameter and 1 centimeter in length, that were completely covered with root hairs.

Journal Article↗
PubMed2006

Actin organization during eucalyptus root hair development and its response to fungal hypaphorine.

The fungus Pisolithus microcarpus establishes an ectomycorrhiza with Eucalyptus globulus. This symbiosis involves a fungal synthesis and secretion of hypaphorine, an indolic compound. Previous studies have shown that hypaphorine induces an alteration in the actin cytoskeleton of elongating root hairs and inhibits hair elongation. Using an alternative approved method, we analyzed the effects of hypaphorine on the E. globulus root hair cyto-architecture and actin configuration in more detail and provide new results. One mM hypaphorine stops root hair elongation within 20 min, and changes the hair cyto-architecture. Semi-quantitative analysis of the actin cytoskeleton before and after treatment with hypaphorine shows that hypaphorine induces a shift from fine F-actin to F-actin bundles in the sub-apex of the hair, which occurs first in the mid-plane of the cell. This creates a sub-apical cell centre free of filamentous actin, an actin configuration that differs from that during developmental growth arrest. The mechanism of action of hypaphorine is discussed.

Actins↗
PubMed2000

[Dynamics of mitotic index of buckwheat root meristems, developing from seeds subjected to percussive wave treatment].

A method of percussive wave treatment of seeds, promoting activization of physiological processes in plants, was proposed. The influence of physical treatment on cell nuclei and phytohormones was investigated. We examined dynamics of mitotic indices (MI) of the root meristems of buckwheat seedlings 48-58 h after the treatment. The seeds were treated with pressures of 11, 23, 29 MPa. The synchrony of cell divisions was estimated according to the augmentation of maximum MI versus average MI. The maximum and the average MI of control seedlings was 9.6 and 8.1%, resp. After the treatment with the pressure of 11 MPa the average MI increased by 2.6 times, and synchrony raised by 50%. After the treatment by the pressure of 23 MPa the average value of MI did not change versus the control, but the synchrony enhanced by 2.8 times. After the treatment of the pressure of 29 MPa the average MI decreased by 31%, the synchrony increased by 33%. Examination of phase indexes allowed to reveal the damage of cytotomy, transition to metaphase, and mitotic apparatus formation. The MI of root meristems of the test seedling aged 8 days topped the control by 21, 156 and 20%. So, the pressure of 11 MPa promoted MI increase in 2 days, and those of 23 and 29 MPa in 8 days. The investigation of hormone balance allowed to detect a raising level of abscisic acid. Its influence on the plant growth depends on the content of zeatin. A hypothetical model of plant reaction mechanism was proposed, based on the obtained results. A momentary pressing in the percussive wave was a stressor, promoting the accumulation of ABA and "growth rest", that changed for an active growth induced by zeatin.

Fagopyrum↗
PubMed2006

Spontaneous re-eruption of intruded permanent incisors: five case reports.

This report presents 5 cases of intrusive luxation in immature permanent central incisors. The intruded incisors, with careful monitoring, were allowed to spontaneously re-erupt, which avoided the need to reposition the tooth either orthodontically or surgically. All of the teeth re-erupted spontaneously in a few months. The root development continued in all of the cases and all pulps remained vital. There were no other signs of pulpal and/or periapical pathology. It can be concluded that intruded immature permanent teeth can spontaneously re-erupt, conserve their vitality, and continue their root development without any surgical or orthodontic management.

Child↗
PubMed2001

Variations in phytoremediation performance with diesel-contaminated soil.

The potential for phytoremediation of high concentrations of petroleum hydrocarbons is poorly understood. This study examines variations in phytoremediation performance for a soil contaminated with diesel at 6400 mg TPH kg-1 dry mixture. Experiments on diesel-contaminated soil were conducted in cups using 200 g of soil, and in columns using 4,000 g. Root development and TPH levels were measured in both experiments. In addition, CO2 soil gas concentrations were measured in the column experiments. The results show that ryegrass enhanced the loss of TPH over controls, and that this benefit only became evident after full root establishment. A comparison of the two experiments shows that rooting intensity (mg root kg-1 soil) is the key factor leading to higher TPH loss rates in the smaller containers. No clear difference in TPH loss occurred at 100 and 260 mm depths. Soil gas CO2 did not correlate well with TPH loss rates. The research concludes that an understanding of root development is crucial to evaluating the potential for ryegrass phytoremediation.

Atmosphere Exposure Chambers↗
PubMed1989

[Study of trace elements in bovine permanent teeth germ].

It is well documented that uptake of various trace elements take place during tooth development. The purpose of this experiment was to analyze the uptake amount of these various trace elements, in particular Cd, Zn, Pb and Cu throughout the tooth germ formation all the way up to the eruption stage. Bovine permanent tooth germs were used in this experiment. Instead of the conventional morphologic stages, further subdivision into eight groups were employed. The resultant findings were as follows: 1) Uptake of Cd and Zn were verified during the root development to early tooth eruption stage in enamel. Meanwhile, for dentin, the uptake was corroborated from the root development to the late tooth eruption stage. 2) Uptake of Cu was verified during the late tooth eruption stage in enamel. However, no uptake occurred in dentin in any of the various stages. 3) Uptake of Pb occurred during the late tooth eruption stage in enamel. Meanwhile, in dentin, constant equivalent amount of uptake was seen throughout all of the stages. 4) Quantitative analysis of the Cd, Zn and Pb uptake in both enamel and dentin clearly indicated that enamel showed much higher values. The uptake of Cu was found to be significantly high in the groups of the coronal one-third and the eruption four-fifth groups for enamel. Meanwhile, the crown completion group to the half erupted group showed significantly high values for dentin. Based on the above findings, one can deduce clear correlation between enamel organ development and the uptake of the said various trace elements.

Animals↗
PubMed1991

Synchronous expression of leghaemoglobin genes in Medicago truncatula during nitrogen-fixing root nodule development and response to exogenously supplied nitrate.

Two leghaemoglobin genes from the diploid, autogamous Medicago truncatula (Mtlb1 and Mtlb2) have been cloned and their nucleotide sequences determined. The deduced amino acid sequences encoded by these two genes differ significantly (18%), confirming that they belong to different sub-groups of Medicago leghaemoglobin genes. RNAse protection experiments have been used to show that both genes are transcriptionally active, and are expressed specifically in the nitrogen-fixing root nodule of M. truncatula. Whilst Mtlb1 mRNA is present at approximatively 3-fold higher steady-state levels than Mtlb2 mRNA, the transcription of both genes is triggered concomitantly during nodule development (5 days after inoculation with Rhizobium meliloti), and the ratio of the steady-state levels of the two mRNA species remains constant throughout nodule maturation. When the growth medium of nodulated M. truncatula is supplemented with 5 mM KNO3 over a period of 2-3 days there is a progressive drop in specific nitrogen fixation activity to only 20-25% of the original level. This is accompanied with a parallel and synchronous reduction in the quantities of mRNA corresponding to both Mtlb1 and Mtlb2. By contrast, the expression of the nodule parenchyma-specific gene ENOD2 is not significantly modified following nitrate treatment, clearly demonstrating differences in tissue-specific gene regulation in response to combined nitrogen.

Amino Acid Sequence↗
PubMed2004

Chromosomes associate premeiotically and in xylem vessel cells via their telomeres and centromeres in diploid rice ( Oryza sativa).

Studies of the meiosis of diploid plants such as Arabidopsis, maize and diploid progenitors of wheat have revealed no premeiotic association of chromosomes. Premeiotic and somatic association of chromosomes has only been previously observed in the anther tissues and xylem vessel cells of developing roots in polyploid plants such as hexaploid and tetraploid wheat, polyploid relatives of wheat and artificial polyploids made from the progenitor diploids of wheat. This suggested that this association was confined specifically to polyploids or was induced by polyploidy. However, we developed procedures for in situ hybridization on structurally well-preserved tissue sections of rice, and analysed two diploid rice species ( Oryza sativa and O. punctata). Contrary to expectation, this has revealed that centromeres and telomeres also associate both in the xylem vessel cells of developing root and in undifferentiated anther cells in these diploids. However, in contrast to wheat and related polyploids, where the initial association in undifferentiated anthers is between either non-homologous or related chromosomes, and not homologous chromosomes, the initial association of rice chromosomes seems to be between homologues. Thus, in contrast to the diploid dicot model Arabidopsis, meiotic studies on the diploid model cereal, rice, will now need to take into account the effects of premeiotic chromosome association.

Centromere↗
PubMed1990

Expression of attachment proteins during cementogenesis.

There is general agreement that during development the extracellular environment plays a critical role in controlling cell differentiation. Data generated from numerous studies support the possibility that cell attachment proteins and their corresponding cell receptors are possible candidates for this role. In particular, our studies are directed at identifying attachment proteins in mature cementum and establishing the function of these proteins during root formation. Fractionation of guanidine HCL/EDTA extracts of cementum revealed the presence of a bone-associated attachment, BSP, as well as fractions containing as of yet undetermined attachment proteins. Immunofluorescent examination of 1st molar tissues during root formation, obtained from 7 day-old mice neonates, for bone-associated attachment proteins indicated that osteopontin is expressed in the area of Hertwig's epithelial root sheath, but not in the region of the dental papillae. However, dental papillae cells, considered to have the capacity to form cementum, attached to osteopontin coated dishes, in vitro. Thus, unique attachment proteins, as well as those previously identified, were found in mature cementum and during root development. Future studies focused on identifying attachment proteins of mature cementum and determining the spatial and temporal localization of these proteins, pre- and post-cementogenesis, will provide important information necessary for establishing the function of these proteins during root development.

Animals↗
PubMed1992

Effect of root canal infection and treatment of traumatized primary incisors on their permanent successors.

The purpose of the present retrospective study was to evaluate the effect of trauma, root canal infection and treatment of non-vital primary incisors on their permanent successors. A total of 117 permanent central incisors were examined clinically and radiographically for the presence of discolorations, hypoplasia, or disturbances in root development. Of these, 29 were succedaneous to traumatized, endodontically involved and treated primary incisors (Group A). Another 29 had their traumatized, endodontically involved, primary predecessors extracted or left untreated (Group B). The remaining 59 incisors were intact and had no history of trauma (Group C). Severe hypoplasia could not be observed in any of the teeth, and no disturbances in root development could be disclosed radiographically. The incidence of defects in Groups B and C was similar, whereas in Group A it was 2 or 3 times higher than in each of the other two groups. Despite this fact, root canal treatment of traumatized non-vital primary incisors should be considered a treatment option, as premature extraction of a primary incisor may lead to speech problems, premature eruption and/or malalignment of the permanent successor, or affect the child's self image.

Chi-Square Distribution↗
PubMed2004

Expression of insulin-like growth factor-1 receptor in human pulp tissue.

Insulin-like growth factor-1 (IGF-1) plays an important role in cell proliferation and differentiation. The purpose of this study was to use a radioreceptor assay to evaluate whether IGF-1 receptors are present in human pulp and to determine whether differences in its expression are found in the pulp tissue of teeth having incomplete or complete root development. Twenty pulps were obtained from freshly extracted human third molars; they were then processed and labeled with I-IGF-1. The results showed IGF-1 receptor expression in all human pulp samples. t test revealed statistically significant higher expression in the pulps from teeth having incomplete root development (P <0.005). Given the functions of this growth factor system in other tissues, the present findings are consistent with the hypothesis that IGF-1 contributes toward forming and mineralizing dental tissues as well as in pulp-repairing processes.

Adolescent↗
PubMed1996

Synchronous onset of NGF and TrkA survival dependence in developing dorsal root ganglia.

Determinations of dorsal root ganglion (DRG) neuron loss in nerve growth factor (NGF) and neurotrophin-3 (NT-3) null mutant mice have supported the concept that neurons can switch neurotrophin dependence by revealing that many neurons must require both of these factors acting either sequentially or simultaneously during development. The situation is complex, however, in that NT-3(-/-) mutant mice show far greater neuron loss than mice deficient in the NT-3 receptor TrkC, suggesting that NT-3 may support many DRG neurons via actions on the NGF receptor TrkA. To assess the possibility of ligand-receptor cross-talk as a developmental mechanism, we have compared the onset of survival dependence of lumbar DRG neurons on NT-3, TrkC, NGF, and TrkA signaling in mice deficient in these molecules as a result of gene targeting. At embryonic day 11.5 (E11.5), virtually all lumbar DRG cells express TrkC mRNA and many require NT-3 and TrkC signaling for survival. In contrast, although many lumbar DRG cells also express TrkA at E11.5, there is little survival dependence on TrkA signaling. By E13.5, most lumbar DRG cells have downregulated TrkC mRNA. The onset of survival dependence on NGF and TrkA-signaling is concurrent and of equal magnitude at E13.5, demonstrating that NT-3 alone does not support DRG neurons via TrkA, nor can NT-3 compensate for the loss of NGF. We conclude that many murine DRG cells require NT-3 activation of TrkA is unimportant to these early NT-3 survival-promoting actions. We suggest that the discrepancy in cell loss between NT-3(-/-) and trkC(-/-) mutants is attributable to the ability of NT-3 to support DRG neurons via TrkA in the artificial situation where TrkC is absent.

Animals↗