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At least 1,261 records · Page 70Linked to original sources
PubMed2004

Correlation of endogenous free polyamine levels with root nodule senescence in different genotypes in Vigna mungo L.

Endogenous free polyamines, nitrogenase (EC 1.1.8.6.1, acetylene reduction), and leghaemoglobin (pyridine-hemochrome assay) levels were compared among five genotypes of developing Vigna root nodules grown under field conditions. Nitrogenase activity and leghaemoglobin level attained a peak at the flowering stage and gradually declined thereafter. Individual and total polyamine also followed the same pattern. Ranking on the basis of legume yield and other morphometric attributes was PDU-2 > UH-28 > UH-82 > T-9 > Sardhomash. Except spermine, the levels of putrescine, spermidine, and total polyamine showed significant differences (p<0.05) amongst the genotypes, particularly from flowering to mid-pod development stage. Genotype, development stage, and their interaction between the two had significant (p<0.01) effects on individual as well as total polyamines. Moreover, significant high linear correlations were found between total free polyamine and putrescine with conventional nodule senescence marker like nitrogenase (R2 = 0.94 and R2 = 0.92, respectively). Putrescine had an overall positive correlation with high legume yield. The results strongly suggest a relationship between polyamine and nodule senescence. Endogenous free polyamine and putrescine may be considered as genotypic markers for nodule senescence in field grown V. mungo. It is suggested that the flowering stage is more suitable for selection.

Fabaceae↗
PubMed1999

Tissue-specific expression of two genes for sucrose synthase in carrot (Daucus carota L.).

Sucrose synthase, which cleaves sucrose in the presence of uridine diphosphate (UDP) into UDP-glucose and fructose, is thought to be a key determinant of sink strength of heterotrophic plant organs. To determine the roles of the enzyme in carrot, we characterized carrot sucrose synthase at the molecular level. Two genes (Susy*Dc1 and Susy*Dc2) were isolated. The deduced amino acid sequences are 87% identical. However, the sequences upstream of the translation initiation codons are markedly different, as are the expression patterns of the two genes. Susy*Dc2 was exclusively expressed in flowers. Transcripts for Susy*Dc1 were found in stems, in roots at different developmental stages, and in flower buds, flowers and maturing seeds, with the highest levels in strong utilization sinks for sucrose such as growing stems and tap root tips. Expression of Susy*Dc1 was regulated by anaerobiosis but not by sugars or acetate. The carrot sucrose synthase protein is partly membrane-associated and this insoluble form may be directly involved in cellulose biosynthesis. Tap roots of the carrot cultivar used accumulated starch in the vicinity of the vascular bundles, which correlated with high sucrose synthase transcript levels. This finding suggests that soluble sucrose synthase in tap roots channels sucrose towards starch biosynthesis. Starch accumulation appears to be transient and may be involved in sucrose partitioning to developing tap roots.

Anaerobiosis↗
PubMed1998

Tissue localization of expansins in deepwater rice.

Expansins are a family of proteins capable of inducing stress relaxation of isolated cell walls. In earlier studies, we showed that the expression of expansin genes in deepwater rice (Oryza sativa L.) is regulated by developmental, hormonal and environmental stimuli. Here, we describe the spatial distribution pattern of expansin transcripts and proteins in tissues and organs of deepwater rice using in situ mRNA hybridization and immunohistochemical analysis. Expansin transcripts and proteins are present at high levels in the growing internodal epidermis, which has thick cell walls and acts, therefore, as a growth-limiting cell layer. Expansins are also concentrated in the differentiating vascular bundles of internodes. In the primary root, expansins are predominantly expressed in the tip region, particularly in the epidermis, differentiating vascular cylinder, and around the pericyle. Developing adventitious roots and lateral root primordia also contain high levels of expansin mRNA. In the shoot apex, expansin transcripts are abundant in the emerging leaf primordia. Our results indicate that expansins play an important role in the expansion and differentiation of plant tissues and organs.

In Situ Hybridization↗
PubMed1997

Perinatal risk factors and neuromotor behaviour during the neonatal period.

Preterm birth is associated with an increased risk for neurological handicaps. The purpose of the present study has been: to investigate the influence of perinatal risk factors on early neuromotor development during the neonatal period; to specify the neuromotor parameters particularly sensitive to perinatal complications; and to analyse whether the infant's age at test influences the results. Beside examination of passive/active muscle tone and automatic movements (22 parameters) was performed at 36 (101 infants) and 40 (153 infants) gestational weeks. Low birthweight and long treatment on a ventilator had a negative influence on the neuromotor behaviour at 36 weeks' gestation and white matter disturbances strongly affected the neuromotor parameters at 40 weeks. The development of rooting, sucking, swallowing and arm recoil after long-lasting ventilator treatment was affected by several neonatal risk factors. The development of passive muscle tone and several parameters measuring active muscle tone demonstrated individual consistency between tests, i.e. an infant's rank at 36 weeks' gestation was unchanged 4 weeks later, and some other parameters were not as consistent. The present study shows that several perinatal risk factors influence neuromotor behaviour already during the neonatal period. In addition, the present study provides data on the neuromotor behaviour during the neonatal period that will be related to later neurodevelopmental examinations in order to evaluate the prognostic value of testing neuromotor development.

Developmental Disabilities↗
PubMed2005

Cell-to-cell movement of the CAPRICE protein in Arabidopsis root epidermal cell differentiation.

CAPRICE (CPC), a small, R3-type Myb-like protein, is a positive regulator of root hair development in Arabidopsis. Cell-to-cell movement of CPC is important for the differentiation of epidermal cells into trichoblasts (root hair cells). CPC is transported from atrichoblasts (hairless cells), where it is expressed, to trichoblasts, and generally accumulates in their nuclei. Using truncated versions of CPC fused to GFP, we identified a signal domain that is necessary and sufficient for CPC cell-to-cell movement. This domain includes the N-terminal region and a part of the Myb domain. Amino acid substitution experiments indicated that W76 and M78 in the Myb domain are critical for targeted transport, and that W76 is crucial for the nuclear accumulation of CPC:GFP. To evaluate the tissue-specificity of CPC movement, CPC:GFP was expressed in the stele using the SHR promoter and in trichoblasts using the EGL3 promoter. CPC:GFP was able to move from trichoblasts to atrichoblasts but could not exit from the stele, suggesting the involvement of tissue-specific regulatory factors in the intercellular movement of CPC. Analyses with a secretion inhibitor, Brefeldin A, and with an rhd3 mutant defective in the secretion process in root epidermis suggested that intercellular CPC movement is mediated through plasmodesmata. Furthermore, the fusion of CPC to tandem-GFPs defined the capability of CPC to increase the size exclusion limit of plasmodesmata.

Amino Acid Substitution↗
PubMed2003

Interaction of Escherichia coli with growing salad spinach plants.

In this study, the interaction of a bioluminescence-labeled Escherichia coli strain with growing spinach plants was assessed. Through bioluminescence profiles, the direct visualization of E. coli growing around the roots of developing seedlings was accomplished. Subsequent in situ glucuronidase (GUS) staining of seedlings confirmed that E. coli had become internalized within root tissue and, to a limited extent, within hypocotyls. When inoculated seeds were sown in soil microcosms and cultivated for 42 days, E. coli was recovered from the external surfaces of spinach roots and leaves as well as from surface-sterilized roots. When 20-day-old spinach seedlings (from uninoculated seeds) were transferred to soil inoculated with E. coli, the bacterium became established on the plant surface, but internalization into the inner root tissue was restricted. However, for seedlings transferred to a hydroponic system containing 10(2) or 10(3) CFU of E. coli per ml of the circulating nutrient solution, the bacterium was recovered from surface-sterilized roots, indicating that it had been internalized. Differences between E. coli interactions in the soil and those in the hydroponic system may be attributed to greater accessibility of the roots in the latter model. Alternatively, the presence of a competitive microflora in soil may have restricted root colonization by E. coli. The implications of this study's findings with regard to the microbiological safety of minimally processed vegetables are discussed.

Colony Count, Microbial↗
PubMed2003

crinkle, a novel symbiotic mutant that affects the infection thread growth and alters the root hair, trichome, and seed development in Lotus japonicus.

To elucidate the mechanisms involved in Rhizobium-legume symbiosis, we examined a novel symbiotic mutant, crinkle (Ljsym79), from the model legume Lotus japonicus. On nitrogen-starved medium, crinkle mutants inoculated with the symbiont bacterium Mesorhizobium loti MAFF 303099 showed severe nitrogen deficiency symptoms. This mutant was characterized by the production of many bumps and small, white, uninfected nodule-like structures. Few nodules were pale-pink and irregularly shaped with nitrogen-fixing bacteroids and expressing leghemoglobin mRNA. Morphological analysis of infected roots showed that nodulation in crinkle mutants is blocked at the stage of the infection process. Confocal microscopy and histological examination of crinkle nodules revealed that infection threads were arrested upon penetrating the epidermal cells. Starch accumulation in uninfected cells and undeveloped vascular bundles were also noted in crinkle nodules. Results suggest that the Crinkle gene controls the infection process that is crucial during the early stage of nodule organogenesis. Aside from the symbiotic phenotypes, crinkle mutants also developed morphological alterations, such as crinkly or wavy trichomes, short seedpods with aborted embryos, and swollen root hairs. crinkle is therefore required for symbiotic nodule development and for other aspects of plant development.

Cell Surface Extensions↗
PubMed2004

ENHANCER of TRY and CPC 2 (ETC2) reveals redundancy in the region-specific control of trichome development of Arabidopsis.

An evolutionarily conserved set of proteins consisting of MYB and bHLH transcription factors and a WD40 domain protein is known to act in concert to control various developmental processes including trichome and root hair development. Their function is difficult to assess because most of them belong to multigene families and appear to act in a redundant fashion. In this study we identified an enhancer of the two root hair and trichome patterning mutants triptychon (try) and caprice (cpc), enhancer of try and cpc2 (etc2). The ETC2 gene shows high sequence similarity to the single-repeat MYB genes CPC and TRY. Overexpression results in the suppression of trichomes and overproduction of root hairs similarly as observed for TRY and CPC suggesting that ETC2 has similar biochemical properties. The etc2 single mutant shows an increase in trichome number on leaves and petioles. Double and triple mutant analysis indicates that the ETC2 gene acts redundant with TRY and CPC in trichome patterning.

Amino Acid Sequence↗
PubMed2000

Changes in cell structure during the formation of root aerenchyma inSAGITTARIA LANCIFOLIA (Alismataceae).

In many wetland species, root aerenchyma is produced by the predictable collapse of root cortex cells, indicating a programmed cell death (PCD). The objective of this study was to characterize the cellular changes that accompany this PCD in the marsh species Sagittaria lancifolia. Structural changes in membranes and organelles were examined during development of root cortex cells to compare with previous examples of PCD. The organization of cortical microtubule (CMT) arrays in root cells from S. lancifolia was also evaluated as a possible predictor of cell lysis. Nuclear fragmentation and condensation were the earliest changes observed in cells undergoing lysis. Breakdown of the tonoplast and other organelles and disruption of the plasma membrane followed. After loss of cytoplasm, cells collapsed to form gas spaces. These results were compared to collapse of root cortical cells of Zea mays and Oryza sativa during aerenchyma development. Changes in the appearance of the cytoplasm of all three species were similar at later stages of aerenchyma development. The relative timing of disintegration of the tonoplast and middle lamella appeared to differ among the three species. Changes in the organization of CMT arrays did not appear to be a predictor of PCD in S. lancifolia. Aerenchyma production in plants involves a type of PCD that is morphologically distinct from PCD described from many animals.

Journal Article↗
PubMed2006

Spontaneous root-nodule formation in the model legume Lotus japonicus: a novel class of mutants nodulates in the absence of rhizobia.

Root-nodule development in legumes is an inducible developmental process initially triggered by perception of lipochitin-oligosaccharide signals secreted by the bacterial microsymbiont. In nature, rhizobial colonization and invasion of the legume root is therefore a prerequisite for formation of nitrogen-fixing root nodules. Here, we report isolation and characterization of chemically induced spontaneously nodulating mutants in a model legume amenable to molecular genetics. Six mutant lines of Lotus japonicus were identified in a screen for spontaneous nodule development under axenic conditions, i.e., in the absence of rhizobia. Spontaneous nodules do not contain rhizobia, bacteroids, or infection threads. Phenotypically, they resemble ineffective white nodules formed by some bacterial mutants on wild-type plants or certain plant mutants inoculated with wild-type Mesorhizobium loti. Spontaneous nodules formed on mutant lines show the ontogeny and characteristic histological features described for rhizobia-induced nodules on wild-type plants. Physiological responses to nitrate and ethylene are also maintained, as elevated levels inhibit spontaneous nodulation. Activation of the nodule developmental program in spontaneous nodules was shown for the early nodulin genes Enod2 and Nin, which are both upregulated in spontaneous nodules as well as in rhizobial nodules. Both monogenic recessive and dominant spontaneous nodule formation (snf) mutations were isolated in this mutant screen, and map positions were determined for three loci. We suggest that future molecular characterization of these mutants will identify key plant determinants involved in regulating nodulation and provide new insight into plant organ development.

Gene Expression Regulation, Plant↗
PubMed1992

cDNA sequence and expression of a phosphoenolpyruvate carboxylase gene from soybean.

A full-length cDNA encoding a subunit of phosphoenolpyruvate carboxylase (PEPC) was isolated from a developing seed expression library of the C3 plant Glycine max. The corresponding mRNA is present at similar levels in leaf, stem, root and developing seed. Two potential start codons exist, and the activity of protein initiated from the first such codon could be subject to regulation by protein kinase. Sequence comparison shows a similar upstream start codon in the case of the Ppc2 gene from Mesembryanthemum crystallinum, previously assumed to lack the sequences necessary for phosphorylation. The soybean encoded protein tends to resemble other 'C3-type' PEPC proteins more closely than those implicated in C4 or crassulacean acid metabolism.

Amino Acid Sequence↗
PubMed2004

Solute transport and extraction by a single root in unsaturated soils: model development and experiment.

A contaminant transport model was developed to simulate the fate and transport of organic compounds such as TNT (2,4,6-trinitrotoluene), using the single-root system. Onions were planted for this system with 50-ml plastic tubes. Mass in the soil, soil solution, root and leaf was monitored using 14C-TNT. Model parameters were acquired from the experiments in the single-root system and were used to simulate total TNT concentration in soil, providing the average concentrations in the rhizosphere and bulk soil as well as root and leaf compartments. Because the existing RCF (root concentration factor) and TSCF (transpiration stream concentration factor) equations based on logKow (octanol-water partition coefficient) were not correlated to TNT uptake, a new term, root uptake rate (Rur), and a new Tscf equation, based on the experimental data, were introduced in the proposed model. The results from both modeling and experimental studies showed higher concentrations of TNT in the rhizosphere than in the bulk soil, because mass transported from the surrounding soil into the rhizosphere was higher than that by root uptake.

Biodegradation, Environmental↗
PubMed1991

Aortic valve/root interactions in porcine hearts: implications for bioprosthetic valve sizing.

The implantation of aortic allografts as well as stentless, freehand porcine xenograft valves requires proper sizing of the graft for the recipient aortic root. To visualize the aortic valve in motion and measure the cyclic expansion of the aortic root, we developed an isolated porcine heart model and a computerized three-dimensional reconstruction technique. Dynamic and static expansions of the aortic root were obtained from beating and arrested porcine hearts, and additional static expansions at varying pressures were measured from reconstructed three-dimensional models of valves obtained with high-resolution magnetic resonance imaging. Measurements of aortic root expansion have shown that it is highly dependent upon the pressures imposed on the heart. Although the aortic root expanded by only 5% between systolic pressures of 60 and 100 mmHg, the total expansion was up to 40% between rest and cyclic pressurizing to 100 mmHg. This data suggest that unstented xenograft valves should be sized 30% to 40% larger than the collapsed size of the recipient aorta. Proper sizing of valves on stents should also be attempted to reduce the large amount of leaflet redundancy that current stenting techniques produce.

Animals↗
PubMed1995

Arabidopsis COP1 protein specifically interacts in vitro with a cytoskeleton-associated protein, CIP1.

Arabidopsis COP1 acts inside the nucleus to suppress photomorphogenic cellular development, and light inactivation of COP1 may involve a specific control of its nuclear activity in hypocotyls and cotyledons, but not in roots, of developing seedlings. To understand the molecular mechanisms of COP1 action during light-mediated development, we initiated a screen for Arabidopsis cDNAs encoding proteins which interact directly with COP1 in vitro as a step to identify the cellular components involved. We report here the isolation and characterization of a cDNA clone encoding a protein designated CIP1 (COP1-interactive protein 1). CIP1 is predominantly alpha-helical and most likely involved in coiled-coil formation. It interacts specifically with the putative coiled-coil region of COP1 in vitro. Further, CIP1 is encoded by a single gene in Arabidopsis, and its mRNA and protein levels are not regulated by light. Immunofluorescent labeling of CIP1 in Arabidopsis seedling protoplasts demonstrated that CIP1 is part of, or associated with, a cytoskeletal structure in hypocotyl and cotyledon cells, but not in roots. Our results are consistent with a possible role of CIP1 in mediating light control of COP1 nuclear activity by regulating its nucleocytoplasmic partitioning.

Amino Acid Sequence↗
PubMed2006

Clinical evaluation of tunneled molars: a retrospective study.

BACKGROUND: The main concern associated with the tunneling procedure is the development of root caries on the furcation area post-treatment. The objective of this study was to evaluate the periodontal conditions and the prevalence of root caries in tunneled molars. METHODS: The study sample comprised 30 tunneled teeth (mean tunneling age = 3.6 years) in 18 subjects who had received periodontal treatment and were enrolled in a maintenance program that included the application of fluoride to the exposed root surfaces. Plaque index (PI), pocket depth (PD), bleeding on probing (BOP), decayed, missing, filled or sound teeth (DMFT) and demographic characteristics were assessed. Statistical analysis was performed using the Friedman and Mann-Whitney tests and multiple linear regression analyses. RESULTS: Four teeth (13.4%) showed active root caries inside the tunnels. Six (5.4%) of the 109 root surfaces facing the furcation region (inner surfaces) were affected by carious lesions, similar to the amount of root caries observed on the outer tunnel root surfaces, where 10 (5.3%) of the 189 surfaces studied were restored (p > 0.05). The interior of the tunnels had a higher percentage of sites with PD > or =6 mm then the exterior (p > 0.05). However, the plaque indexes and BOP scores were low for both the internal and external surfaces of the tunnels. Regression analysis indicated that the only positive association with the development of caries inside the tunnels was previous root caries experience (beta = -0.671; p = 0.01). CONCLUSION: The results show that tunneling is a suitable technique to treat periodontal furcation lesions in individuals following a regular maintenance program.

Adult↗
PubMed1988

Axon classes and internodal growth in the ventral spinal root L7 of adult and developing cats.

Internodal length, number of myelin sheath lamellae and axon diameter were estimated in samples of nerve fibres reconstructed from transverse sections (EM and LM) of the L7 ventral spinal root of adult cats, kittens and cat fetuses. The axon calibre spectrum was unimodal in the youngest fetuses, became bimodal at 47 days after mating, i.e. about 2 weeks before birth (63 days after mating) and trimodal at 1 week of postnatal age. Alpha-axons received myelin during the period 40-45 to 50-55 days after mating while gamma-axons became myelinated from 60-63 days after mating to 2-3 weeks of postnatal age. The mean length of the first completely myelinated internodes measured 139 microns and 209 microns in the alpha- and gamma-fibre group respectively. The adult mean values were 1390 microns and 640 microns respectively. The average internodal elongation was x 10 and x 3 in the two fibre groups, whereas the longitudinal growth of the whole ventral root was x 5.4 and x 3.5. A combined linlog function could be fitted to describe the regression between internodal length and axon diameter and was established from birth onwards. The separate alpha- and gamma-fibre samples were best described by linear functions, the alpha internodal length being independent of axon diameter while the gamma internodal length increased linearly with axon diameter. The amount of internodal myelin increased linearly with increasing mantle area of the internodal axon. The mean amount of internodal myelin of alpha-fibres showed two periods of intense growth; one from the start of myelination to 2 months postnatally and the other between 4 and 6 months of age. The mean length of the lamellar spiral forming the myelin sheath showed about the same increase per unit length of axon circumference (about 160:1) in both alpha- and gamma-fibre groups as long as longitudinal internodal growth persisted.

Age Factors↗