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PubMed2006

The homeobox gene GLABRA2 affects seed oil content in Arabidopsis.

Despite a good understanding of genes involved in oil biosynthesis in seed, the mechanism(s) that controls oil accumulation is still not known. To identify genes that control oil accumulation in seed, we have developed a simple screening method to isolate Arabidopsis seed oil mutants. The method includes an initial screen for seed density followed by a seed oil screen using an automated Nuclear Magnetic Resonance (NMR). Using this method, we isolated ten low oil mutants and one high oil mutant. The high oil mutant, p777, accumulated 8% more oil in seed than did wild type, but it showed no differences in seed size, plant growth or development. The high-oil phenotype is caused by the disruption of the GLABRA2 gene, a previously identified gene that encodes a homeobox protein required for normal trichome and root hair development. Knockout of GLABRA2 did not affect LEAFY COTYLEDON 1 and PICKLE expression in developing embryo. The result indicates that in addition to its known function in trichome and root hair development, GLABRA2 is involved in the control of seed oil accumulation.

Adhesives↗
PubMed1993

Expression of antisense nodulin-35 RNA in Vigna aconitifolia transgenic root nodules retards peroxisome development and affects nitrogen availability to the plant.

A nodulin-35 (N-35) cDNA encoding nodule-specific uricase (EC 1.7.3.3.) was isolated from a Vigna aconitifolia (mothbean) root nodule cDNA library. Sequence analysis of Vigna uricase (VN-35) cDNA revealed 90% homology to that of soybean. The VN-35 cDNA was inserted in the antisense orientation downstream of the caMV-35S promoter, and transgenic hairy roots were formed on Vigna plants using Agrobacterium rhizogenes. Infection with Bradyrhizobium (cowpea) gave rise to root nodules on transgenic hairy roots supported by the wild-type shoot. Expression of antisense VN-35 RNA was detected in transgenic nodules on individual roots using polymerase chain reaction (PCR). The nodules expressing antisense VN-35 RNA were smaller in size and showed lower uricase activity than nodules formed on the hairy roots transformed with a binary vector containing beta-glucuronidase (GUS) gene (used as control), and the plants exhibited nitrogen deficiency symptoms. Ultrastructural analysis and immunogold labeling with antibody against soybean N-35 revealed that the growth of peroxisomes was retarded in transgenic nodules expressing antisense VN-35 RNA. These data suggest that a reduction in ureide biosynthesis limits the availability of symbiotically reduced nitrogen to the plant. The nodules of tropical legumes appear to be specialized in nitrogen assimilation and are developmentally controlled to produce and transport ureides.

Base Sequence↗
PubMed2006

Histocytological analysis of callogenesis and somatic embryogenesis from cell suspensions of date palm (Phoenix dactylifera).

BACKGROUND AND AIMS: The date palm is a dioecious perennial species of the Arecaceae for which in vitro micropropagation is essential to ensure the renewal of palm plantations. This study presents a histocytological analysis of the traditional Mauritanian Amsekhsi cultivar beginning from the initial callogenesis and continuing up to the establishment of the cellular embryogenic cell suspensions. The formation of somatic embryos and their development into rooted plants are also described. METHODS: Foliar segments of seedlings cultured in the presence of 2,4-D produced primary calli that were chopped to produce fine friable granular calli that subsequently produced cellular suspensions when transferred to liquid medium. The somatic proembryos that developed after removal of the 2,4-D were plated on agar medium where they developed into rooted plants. Thin sections of tissue fragments taken at each stage of the process were stained using Periodic Acid Schiff and Naphthol Blue-Black. KEY RESULTS: The first cellular divisions were localized close to the vascular vessels of the leaf. The primary calli were obtained within 2 months. Fine friable granular calli grew quickly after the primary calli were chopped. Individual embryogenic cells were identified that rapidly started to divide and developed into globular proembryos. In addition, in the microcalli, breaking zones appeared in the thick pectocellulosic walls which delimited the pluricellular proembryos. The anatomy of somatic embryos is similar to that of zygotic embryos despite a deficit in the accumulation of intracellular proteins. When rooted with NAA, the vitroplants developed a strong orthotropic taproot. CONCLUSIONS: This study contributes to understanding the whole process of somatic embryogenesis, but two specific questions remain to be answered: what factors are involved in the reactivation of the somatic cells at the beginning of the initial callogenesis, and why do the somatic embryos not accumulate proteins in their tissues during maturation?

Arecaceae↗
PubMed1986

Myelin-associated glycoprotein immunoreactive material: an early neuronal marker of dorsal root ganglion cells during chick development.

Immunostaining of myelin-associated glycoprotein (MAG) was performed in chick dorsal root ganglia (DRG) during development. The MAG-immunoreactive material appeared first around 7 days of incubation in immature neurons of DRG. Immunoprecipitates first confined to one pole of nucleus were gradually redistributed in the perinuclear Golgi apparatus of small DRG cells. Thus MAG may be used in the chick embryo as an early marker of primary sensory neurons of class B.

Animals↗
PubMed2005

The Decreased apical dominance1/Petunia hybrida CAROTENOID CLEAVAGE DIOXYGENASE8 gene affects branch production and plays a role in leaf senescence, root growth, and flower development.

Carotenoids and carotenoid cleavage products play an important and integral role in plant development. The Decreased apical dominance1 (Dad1)/PhCCD8 gene of petunia (Petunia hybrida) encodes a hypothetical carotenoid cleavage dioxygenase (CCD) and ortholog of the MORE AXILLARY GROWTH4 (MAX4)/AtCCD8 gene. The dad1-1 mutant allele was inactivated by insertion of an unusual transposon (Dad-one transposon), and the dad1-3 allele is a revertant allele of dad1-1. Consistent with its role in producing a graft-transmissible compound that can alter branching, the Dad1/PhCCD8 gene is expressed in root and shoot tissue. This expression is upregulated in the stems of the dad1-1, dad2, and dad3 increased branching mutants, indicating feedback regulation of the gene in this tissue. However, this feedback regulation does not affect the root expression of Dad1/PhCCD8. Overexpression of Dad1/PhCCD8 in the dad1-1 mutant complemented the mutant phenotype, and RNA interference in the wild type resulted in an increased branching phenotype. Other differences in phenotype associated with the loss of Dad1/PhCCD8 function included altered timing of axillary meristem development, delayed leaf senescence, smaller flowers, reduced internode length, and reduced root growth. These data indicate that the substrate(s) and/or product(s) of the Dad1/PhCCD8 enzyme are mobile signal molecules with diverse roles in plant development.

Alleles↗
PubMed2006

[Genetic analysis of toxic ion tolerance in barley].

The genetic control of high tolerance of toxic aluminum ions in barley Hordeum vulgare L. has been studied. Cultivar Faust I (c-24612) and accession 9736 from Karelia have been compared with aluminum-sensitive cv. Colsess IV (accession c-24626). Analysis of F1, F2BC1, F3, and F4 progenies has shown that the development of roots of cv. Faust I in water medium with aluminum ions is determined by one (AlpF1) or two (AlpF1, AlpF2) genes. The development of roots of accession 9736 is determined by two genes, AlpK1 and AlpK2. The genes have not been not tested for nonidentity. The high tolerance of Faust I shoots are determined by one major tolerance factor and one dominant inhibitor gene, which hampers the manifestation of the dominant tolerance gene. The penetrance of the inhibitor gene may be incomplete. The aluminum sensitivity of roots and 7-day shoots of cv. Faust I is determined by different genetic factors. The response of barley plants to aluminum ions may be determined by small-effect genes.

Aluminum↗
PubMed1995

Tenascin-C expression by neurons and glial cells in the rat spinal cord: changes during postnatal development and after dorsal root or sciatic nerve injury.

We have used in situ hybridization with a digoxigenin-labelled probe for tenascin-C mRNA and immunocytochemistry with antibodies against tenascin-C, glial fibrillary acidic protein, OX-42 and the 200 kDa neurofilament protein to study the expression, distribution and cellular relationships of tenascin-C mRNA and protein in the developing (postnatal) and adult spinal cord of rat, and the effects thereon of dorsal root, ventral root and sciatic nerve injuries. The most interesting finding was that on postnatal day 7 (P7), P14 and in the adult, but not on P0 or P3, a group of neurons in the lumbar ventral horn expressed the tenascin-C mRNA gene. They represented about 5% of ventral horn neurons in the adult and were among the smaller such neurons. Since 40-60% of such cells were lost at P13 following sciatic nerve crush on P0, some were almost certainly motor neurons. In addition, we found that at P0 and P3, mRNA-containing glial cells were widespread in grey and white matter but sparse in the developing dorsal columns; tenascin-C immunofluorescence showed a similar distribution. By P7 there were fewer mRNA-containing cells in the ventral horns and in the area of the dorsal columns containing the developing corticospinal tract where immunofluorescence was also weak. At P14 there were no glial-like mRNA-containing cells in the grey matter; such cells were confined to the periphery of the lateral and ventral white columns but were present throughout the dorsal columns where tenascin-C immunofluorescence was also strong. No glial-like mRNA-containing cells were present in the adult lumbar spinal cord and tenascin-C immunofluorescence was confirmed to irregular patches in the ventral horn, especially around immunonegative cell bodies of small neurons, a zone around the central canal, and a thin zone adjacent to the glia limitans. Thus the expression of tenascin-C is differentially developmentally regulated in the grey matter and in different parts of the white matter. Three days after injury of dorsal roots L4-6, many cells containing tenascin-C mRNA, some identified as glial fibrillary acidic protein-positive astrocytes, were present in the ipsilateral dorsal column, but were rare after longer survivals. Immunoreactivity, however, was elevated in the ipsilateral dorsal column at 3 days, remained high for several months and disappeared at 6.5 months. Dorsal root injury had no effect on tenascin-C mRNA or protein in the grey matter. Sciatic nerve or ventral root injury had no effect on these molecules in any part of the spinal cord.

Animals↗
PubMed1997

Effects of 1,25-dihydroxyvitamin D3 on growth of mouse neuroblastoma cells.

Epitopes of the 1,25-dihydroxyvitamin D(1,25(OH)2D3) receptor have been shown in developing dorsal root ganglia in fetal mice, as well as in cells maintained in culture [Johnson, J.A., Grande, J.P., Windebank, A.J. and Kumar, R., 1,25-Dihydroxyvitamin D3 receptors in developing dorsal root ganglia of fetal rats, Dev. Brain Res., 92 (1996) 120-124]. To investigate a possible role for 1,25(OH)2D3 in neural cell growth and development, a murine neuroblastoma cell line that expresses 1,25(OH)2D3 receptors, was treated with 1,25(OH)2D3. Treatment with 1,25(OH)2D3 resulted in a decrease in cell proliferation, a change in cell morphology, and the expression of protein markers of mature neuronal cells. The decrease in cell proliferation was accompanied by an increase in the expression of nerve growth factor (NGF). Anti-NGF monoclonal antibody added to the growth medium blocked the decrease in cell proliferation caused by 1,25(OH)2D3 treatment. Our results show that the sterol hormone 1,25(OH)2D3, causes a decrease in the proliferation of mouse neuroblastoma cells through alterations in the expression of NGF.

Animals↗
PubMed1995

Preincubation of Bradyrhizobium japonicum with Genistein Accelerates Nodule Development of Soybean at Suboptimal Root Zone Temperatures.

In the soybean (Glycine max [L.] Merr.) N2-fixing symbiosis, suboptimal root zone temperatures (RZTs) slow nodule development, especially at temperatures below 17[deg]C. A step in the infection process that occurs within the first 24 h is particularly sensitive to suboptimal RZT. The first phase in the establishment of the soybean-Bradyrhizobium japonicum symbiosis is the exchange of recognition molecules. The most effective plant-to-bacterium signal is genistein. Binding of genistein to B. japonicum activates many of the B. japonicum nod genes. To our knowledge, the potential of sub-optimal RZT to disrupt this interorganismal signaling has not previously been investigated. Controlled environment experiments were conducted to determine whether the preincubation of B. japonicum with genistein increases soybean nodulation and N2 fixation at suboptimal RZT and whether the time between inoculation and root-hair curling is shortened by genistein application. The results of these experiments indicated that (a) genistein application increased soybean nodulation at suboptimal RZTs (17.5 and 15[deg]C) but not at the optimal RZT (25[deg]C); (b) the period between inoculation and root-hair curling was shortened by inoculation with bradyrhizobia preincubated with genistein; (c) at 17.5 and 15[deg]C RZT, the onset of N2 fixation occurred earlier in plants that received genistein-treated bradyrhizobia than in plants inoculated with untreated bradyrhizobia; (d) over the tested concentration range, genistein application at 15 to 20 [mu]M was the most effective in stimulating nodulation; and (e) between 25 and 15[deg]C, as RZT decreased, there was an increase in the nodulation-stimulating potential of genistein.

Journal Article↗
PubMed2003

A xylogalacturonan epitope is specifically associated with plant cell detachment.

A monoclonal antibody (LM8) was generated with specificity for xyloglacturonan (XGA) isolated from pea (Pisum sativum L.) testae. Characterization of the LM8 epitope indicates that it is a region of XGA that is highly substituted with xylose. Immunocytochemical analysis indicates that this epitope is restricted to loosely attached inner parenchyma cells at the inner face of the pea testa and does not occur in other cells of the testa. Elsewhere in the pea seedling, the LM8 epitope was found only in association with root cap cell development at the root apex. Furthermore, the LM8 epitope is specifically associated with root cap cells in a range of angiosperm species. In embryogenic carrot suspension cell cultures the epitope is abundant at the surface of cell walls of loosely attached cells in both induced and non-induced cultures. The LM8 epitope is the first cell wall epitope to be identified that is specifically associated with a plant cell separation process that results in complete cell detachment.

Antibodies, Monoclonal↗
PubMed2002

Release characteristics of encapsulated formulations incorporating plant growth factors.

The release characteristics of encapsulated formulations containing a combination of plant growth factors (PGF)--plant hormones (IBA, paclobutrazol), nutrients (fertilizers, microelements), and fungicide (prochloraz)--were studied. The formulations were prepared by encapsulating the active ingredients in a polyethylene matrix and, in some cases, subsequently coating the product with polyurethane. Dissolution experiments were carried out with both coated and non-coated formulations to determine the sustained release patterns of the active ingredients. The PGF controlled-release systems obtained have been shown to promote development of root systems, vegetative growth, and reproductive development in cuttings, potted plants, or garden plants of various plant species. These beneficial effects are attributable to the lasting and balanced PGF availability provided by these systems.

Capsules↗
PubMed2000

Expression of AtPRP3, a proline-rich structural cell wall protein from Arabidopsis, is regulated by cell-type-specific developmental pathways involved in root hair formation.

The tightly regulated expression patterns of structural cell wall proteins in several plant species indicate that they play a crucial role in determining the extracellular matrix structure for specific cell types. We demonstrate that AtPRP3, a proline-rich cell wall protein in Arabidopsis, is expressed in root-hair-bearing epidermal cells at the root/shoot junction and within the root differentiation zone of light-grown seedlings. Several lines of evidence support a direct relationship between AtPRP3 expression and root hair development. AtPRP3/beta-glucuronidase (GUS) expression increased in roots of transgenic seedlings treated with either 1-aminocyclopropane-1-carboxylic acid (ACC) or alpha-naphthaleneacetic acid (alpha-NAA), compounds known to promote root hair formation. In the presence of 1-alpha-(2-aminoethoxyvinyl)glycine (AVG), an inhibitor of ethylene biosynthesis, AtPRP3/GUS expression was strongly reduced, but could be rescued by co-addition of ACC or alpha-NAA to the growth medium. In addition, AtPRP3/GUS activity was enhanced in ttg and gl2 mutant backgrounds that exhibit ectopic root hairs, but was reduced in rhd6 and 35S-R root-hair-less mutant seedlings. These results indicate that AtPRP3 is regulated by developmental pathways involved in root hair formation, and are consistent with AtPRP3's contributing to cell wall structure in Arabidopsis root hairs.

Amino Acids↗
PubMed1970

Investigation of plant water relations with divided root systems of soybean.

Soybean (Glycine max) was grown with root systems divided between adjacent cartons containing nutrient solution or soil. By adding polyethylene glycol (Carbowax 6000) to reduce solute potential or withholding water to reduce soil matric potential until water absorption from that side stopped, the root xylem water potential could be ascertained. Carbowax appeared to increase root resistance. An imbalance technique is described with which soil moisture contents of adjacent containers were followed individually. The patterns of water absorption obtained following repeated additions of water or addition of CaCl(2) solutions to one side indicated soil hydraulic conductivity became limiting at a soil water potential of -2 bars. A high concentration of CaCl(2) added to one side greatly reduced transpiration and produced severe plant injury. With part of the root system developing in nutrient solution, growth of roots into and water absorption from soil were slow; however, reduction of solute potential in the solution side greatly increased water absorption from the soil side.

Journal Article↗
PubMed1989

Iron-Stress Induced Redox Activity in Tomato (Lycopersicum esculentum Mill.) Is Localized on the Plasma Membrane.

Tomato plants (Lycopersicum esculentum Mill.) were grown for 21-days in a complete hydroponic nutrient solution including Fe(3+)-ethylenediamine-di(o-hydroxyphenylacetate) and subsequently switched to nutrient solution withholding Fe for 8 days to induce Fe stress. The roots of Fe-stressed plants reduced chelated Fe at rates sevenfold higher than roots of plants grown under Fe-sufficient conditions. The response in intact Fe-deficient roots was localized to root hairs, which developed on secondary roots during the period of Fe stress. Plasma membranes (PM) isolated by aqueous two-phase partitioning from tomato roots grown under Fe stress exhibited a 94% increase in rates of NADH-dependent Fe(3+)-citrate reduction compared to PM isolated from roots of Fe-sufficient plants. Optimal detection of the reductase activity required the presence of detergent indicating structural latency. In contrast, NADPH-dependent Fe(3+)-citrate reduction was not significantly different in root PM isolated from Fe-deficient versus Fe-sufficient plants and proceeded at substantially lower rates than NADH-dependent reduction. Mg(2+)-ATPase activity was increased 22% in PM from roots of Fe-deficient plants compared to PM isolated from roots of Fe-sufficient plants. The results localized the increase in Fe reductase activity in roots grown under Fe stress to the PM.

Journal Article↗
PubMed2004

Potassium carrier TRH1 is required for auxin transport in Arabidopsis roots.

Disruption of the TRH1 potassium transporter impairs root hair development in Arabidopsis, and also affects root gravitropic behaviour. Rescue of these morphological defects by exogenous auxin indicates a link between TRH1 activity and auxin transport. In agreement with this hypothesis, the rate of auxin translocation from shoots to roots and efflux of [3H]IAA in isolated root segments were reduced in the trh1 mutant, but efflux of radiolabelled auxin was accelerated in yeast cells transformed with the TRH1 gene. In roots, Pro(TRH1):GUS expression was localized to the root cap cells which are known to be the sites of gravity perception and are central for the redistribution of auxin fluxes. Consistent with these findings, auxin-dependent DR5:GUS promoter-reporter construct was misexpressed in the trh1 mutant indicating that partial block of auxin transport through the root cap is associated with upstream accumulation of the phytohormone in protoxylem cells. When [K+] in the medium was reduced from 20 to 0.1 mm, wild type roots showed mild agravitropic phenotype and DR5:GUS misexpression in stelar cells. This pattern of response to low external [K+] was also affected by trh1 mutation. We conclude that the TRH1 carrier is an important part of auxin transport system in Arabidopsis roots.

Arabidopsis↗
PubMed2003

Genetic analysis of adventitious root formation with a novel series of temperature-sensitive mutants of Arabidopsis thaliana.

When cultured on media containing the plant growth regulator auxin, hypocotyl explants of Arabidopsis thaliana generate adventitious roots. As a first step to investigate the genetic basis of adventitious organogenesis in plants, we isolated nine temperature-sensitive mutants defective in various stages in the formation of adventitious roots: five root initiation defective (rid1 to rid5) mutants failed to initiate the formation of root primordia; in one root primordium defective (rpd1) mutant, the development of root primordia was arrested; three root growth defective (rgd1, rgd2, and rgd3) mutants were defective in root growth after the establishment of the root apical meristem. The temperature sensitivity of callus formation and lateral root formation revealed further distinctions between the isolated mutants. The rid1 mutant was specifically defective in the reinitiation of cell proliferation from hypocotyl explants, while the rid2 mutant was also defective in the reinitiation of cell proliferation from root explants. These two mutants also exhibited abnormalities in the formation of the root apical meristem when lateral roots were induced at the restrictive temperature. The rgd1 and rgd2 mutants were deficient in root and callus growth, whereas the rgd3 mutation specifically affected root growth. The rid5 mutant required higher auxin concentrations for rooting at the restrictive temperature, implying a deficiency in auxin signaling. The rid5 phenotype was found to result from a mutation in the MOR1/GEM1 gene encoding a microtubule-associated protein. These findings about the rid5 mutant suggest a possible function of the microtubule system in auxin response.

Arabidopsis↗