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Root Hairs (root + hair)

Distribution by Scientific Domains

Life Sciences	69%

Selected Abstracts

Expression of MsPG3-GFP fusions in Medicago truncatula,hairy roots' reveals preferential tip localization of the protein in root hairs

FEBS JOURNAL, Issue 2 2003
Ignacio D. Rodríguez-Llorente
Tip growth is a specialized type of polar growth where new cell wall is deposited in a localized region of the cell, the growing tip. These cells show a characteristic zonation, with a high accumulation of secretory vesicles containing cell wall components at the tip, followed by an organelle-enriched zone. MsPG3 is a Medicago sativa polygalacturonase gene isolated in our laboratory, specifically expressed during the interaction of this plant with its symbiotic partner Sinorhizobium meliloti and which might participate in tip growth processes during symbiosis. We have used MsPG3-GFP fusions to study in vivo protein transport processes and localization during root hair growth. Different MsPG3-GFP fusions were expressed in Medicago truncatula,hairy roots' following a protocol developed for this study and also tested by transient expression in onion epidermal cells. Preferential accumulation of an MsPG3-GFP fusion protein in the tip of the growing root hair at different developmental stages was found, confirming the delivery of MsPG3 to the newly synthesized cell wall. This indicates that this protein may participate in tip growth processes during symbiosis and, in addition, that this fusion could be a useful tool to study this process in plants. [source]

Plant profilin isovariants are distinctly regulated in vegetative and reproductive tissues

CYTOSKELETON, Issue 1 2002
Muthugapatti K. Kandasamy
Abstract Profilin is a low-molecular weight, actin monomer-binding protein that regulates the organization of actin cytoskeleton in eukaryotes, including higher plants. Unlike the simple human or yeast systems, the model plant Arabidopsis has an ancient and highly divergent multi-gene family encoding five distinct profilin isovariants. Here we compare and characterize the regulation of these profilins in different organs and during microspore development using isovariant-specific monoclonal antibodies. We show that PRF1, PRF2, and PRF3 are constitutive, being strongly expressed in all vegetative tissues at various stages of development. These profilin isovariants are also predominant in ovules and microspores at the early stages of microsporogenesis. In contrast, PRF4 and PRF5 are late pollen-specific and are not detectable in other cell types of the plant body including microspores and root hairs. Immunocytochemical studies at the subcellular level reveal that both the constitutive and pollen-specific profilins are abundant in the cytoplasm. In vegetative cell types, such as root apical cells, profilins showed localization to nuclei in addition to the cytoplasmic staining. The functional diversity of profilin isovariants is discussed in light of their spatio-temporal regulation during vegetative development, pollen maturation, and pollen tube growth. Cell Motil. Cytoskeleton 52:22,32, 2002. © 2002 Wiley-Liss, Inc. [source]

Fungal pathogens associated with melon collapse in Spain,

EPPO BULLETIN, Issue 2 2000
J. García-Jiménez
Spain produces 43 200 ha of melons with a considerable export to European markets. In the last 10 years, melon cultivation in Spain has decreased more than 40% due mainly to collapse of the vines caused by soil-borne diseases. Serious economic losses have resulted. In order better to understand the aetiology of this disease, a survey of 217 melon fields throughout the melon production areas of Spain was conducted from 1987 to 1996 to analyse the fungal population associated with roots. In addition, the presence of melon necrotic spot carmovirus (MNSV) was studied in 93 fields. This virus is present mainly in southeastern Spain. The predominant fungal species isolated from 82.5% of sampled fields with symptoms of collapse was Acremonium cucurbitacearum. Roots affected by this fungus show corky brown areas soon after transplanting. Small secondary roots and root hairs become necrotic, although there is continuous production of new rootlets. This process continues until the late stages of the disease. As the fruits approach maturity, the entire plant wilts and dies. Other fungal species associated with melon collapse are: Monosporascus cannonballus (isolated from 29.5% of sampled fields), Macrophomina phaseolina (32.7%) and Rhizoctonia solani (31.8%). Of these, the incidence of M. cannonballus isolated from diseased melons has increased substantially over the past 10 years. Melon collapse in Spain is complex because several fungi capable of causing collapse of the vines are prevalent and often isolated from roots in the same field. In addition, other minor pathogens, such as Rhizopycnis vagum and Plectosporium tabacinum, are frequently isolated from symptomatic vines and may also contribute to the death of the plants. [source]

Expression of MsPG3-GFP fusions in Medicago truncatula,hairy roots' reveals preferential tip localization of the protein in root hairs

Genotypic variation of potato for phosphorus efficiency and quantification of phosphorus uptake with respect to root characteristics

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2009
Tesfaye Balemi
Abstract Potato (Solanum tuberosum L.), an important food crop, generally requires a high amount of phosphate fertilizer for optimum growth and yield. One option to reduce the need of fertilizer is the use of P-efficient genotypes. Two efficient and two inefficient genotypes were investigated for P-efficiency mechanisms. The contribution of root traits to P uptake was quantified using a mechanistic simulation model. For all genotypes, high P supply increased the relative growth rate of shoot, shoot P concentration, and P-uptake rate of roots but decreased root-to-shoot ratio, root-hair length, and P-utilization efficiency. Genotypes CGN 17903 and CIP 384321.3 were clearly superior to genotypes CGN 22367 and CGN 18233 in terms of shoot,dry matter yield and relative shoot-growth rate at low P supply, and therefore can be considered as P-efficient. Phosphorus efficiency of genotype CGN 17903 was related to higher P-utilization efficiency and that of CIP 384321.3 to both higher P-uptake efficiency in terms of root-to-shoot ratio and intermediate P-utilization efficiency. Phosphorus-efficient genotypes exhibited longer root hairs compared to inefficient genotypes at both P levels. However, this did not significantly affect the uptake rate and the extension of the depletion zone around roots. The P inefficiency of CGN 18233 was related to low P-utilization efficiency and that of CGN 22367 to a combination of low P uptake and intermediate P-utilization efficiency. Simulation of P uptake revealed that no other P-mobilization mechanism was involved since predicted uptake approximated observed uptake indicating that the processes involved in P transport and morphological root characterstics affecting P uptake are well described. [source]

Plant responses to drought and phosphorus deficiency: contribution of phytohormones in root-related processes

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2005
Lutz Wittenmayer
Abstract Environmental stresses are one of the most limiting factors in agricultural productivity. A large portion of the annual crop yield is lost to pathogens (biotic stress) or the detrimental effects of abiotic-stress conditions. There are numerous reports about chemical characterization of quantitatively significant substrate fluxes in plant responses to stress factors in the root-rhizosphere system, e.g., nutrient mobilization, heavy-metal and aluminum immobilization, or establishment of plant-growth-promoting rhizobacteria (PGPR) by exudation of organic anions, phytosiderophores, or carbohydrates into the soil, respectively. The hormonal regulation of these responses is not well understood. This paper highlights this complex process, stressing the involvement of phytohormones in plant responses to drought and phosphorus deficiency as examples. Beside ethylene, abscisic acid (ABA) plays an important role in drought-stress adaptation of plants. This hormone causes morphological and chemical changes in plants, ensuring plant survival under water-limited conditions. For example, ABA induces stomata closure, reduction in leaf surface, and increase in root : shoot ratio and, thus, reduction in transpiration and increase in soil volume for water uptake. Furthermore, it supports water uptake in soil with decreasing water potential by osmotic adjustment. Suitability of hormonal parameters in the selection for improving stress resistance is discussed. Auxins, ethylene, and cytokinins are involved in morphological adaption processes to phosphorus (P) deficiency (increase in root surface, e.g., by the formation of more dense root hairs or cluster roots). Furthermore, indole-3-acetic acid increases root exudation for direct and indirect phosphorus mobilization in soil. Nevertheless, the direct use of the trait "hormone content" of a particular plant organ or tissue, for example the use of the drought-stress-induced ABA content of detached leaves in plant breeding for drought-stress-resistant crops, seems to be questionable, because this procedure does not consider the systemic principle of hormonal regulation in plants. Reaktionen von Pflanzen auf Trockenstress und Phosphormangel: Die Rolle von Phytohormonen in wurzelbezogenen Prozessen Umweltstress stellt den wesentlichsten Limitierungsfaktor für die landwirtschaftliche Produktion dar. Ein erheblicher Teil der jährlichen Ernten geht durch pathogene Organismen (biotischer Stress) oder durch die verheerende Wirkung abiotischer Stressoren verloren (v. a. Trockenstress und Nährstoffmangel). Es gibt zahlreiche Untersuchungen zur stofflichen Charakterisierung der pflanzlichen Stressreaktion an der Wurzel, z.,B. Nährstoffmobilisierung, Schadstoffimmobilisierung oder Etablierung von wachstumsfördernden Rhizobakterien durch Wurzelabscheidungen. Die hormonelle Steuerung dieser Prozesse ist bisher weniger erforscht. Der Artikel geht dieser Problematik am Beispiel von Trockenstress und Phosphormangel unter besonderer Berücksichtigung von Phytohormonen nach. Bei der Anpassung von Pflanzen an Wassermangelbedingungen spielt neben Ethylen das Phytohormon Abscisinsäure (ABA) eine wichtige Rolle. Es induziert morphologische und chemische Veränderungen in der Pflanze, die ein Überleben unter Wassermangelbedingungen ermöglichen. Beispielsweise induziert die ABA den Stomataschluss, eine Verringerung der Blattoberfläche sowie eine Erhöhung des Wurzel:Spross-Verhältnisses und bewirkt dadurch eine verringerte Transpiration und Vergrößerung des Bodenvolumens zur Erschließung von Wasservorräten. Darüber hinaus kann eine ABA-induzierte Anreicherung von osmotisch wirksamen Verbindungen zur Wasseraufnahme bei sinkendem Wasserpotential im Boden beitragen. Bei Phosphat (P)-Mangel sind vor allem Auxine, Cytokine und Ethylen an der morphologischen Anpassung der Wurzeln (Vergrößerung der Wurzeloberfläche durch verstärkte Bildung von Wurzelhaaren oder Proteoidwurzeln) beteiligt. Darüber hinaus bewirkt Indolyl-3-Essigäure eine Intensivierung der Abgabe von Wurzelabscheidungen zur direkten oder indirekten P-Mobilisierung in der Rhizosphäre. Trotzdem wird die unmittelbare Verwendung des Indikators "Hormongehalt" eines bestimmten Pflanzenorganes, beispielsweise der trockenstressinduzierte ABA-Gehalt von abgeschnittenen Blättern, für die Züchtung auf Stressresistenz als problematisch angesehen, da sie das systemische Prinzip der Hormonregulation nicht berücksichtigt. [source]

Monitoring the colonization of sugarcane and rice plants by the endophytic diazotrophic bacterium Gluconacetobacter diazotrophicus marked with gfp and gusA reporter genes

LETTERS IN APPLIED MICROBIOLOGY, Issue 3 2010
L.F.M. Rouws
Abstract Aims:, To evaluate the colonization process of sugarcane plantlets and hydroponically grown rice seedlings by Gluconacetobacter diazotrophicus strain PAL5 marked with the gusA and gfp reporter genes. Methods and Results:, Sugarcane plantlets inoculated in vitro with PAL5 carrying the gfp::gusA plasmid pHRGFPGUS did not present green fluorescence, but ,-glucuronidase (GUS)-stained bacteria could be observed inside sugarcane roots. To complement this existing inoculation methodology for micropropagated sugarcane with a more rapid colonization assay, we employed hydroponically grown gnotobiotic rice seedlings to study PAL5,plant interaction. PAL5 could be isolated from the root surface (108 CFU g,1) and from surface-disinfected root and stem tissues (104 CFU g,1) of inoculated plants, suggesting that PAL5 colonized the internal plant tissues. Light microscopy confirmed the presence of bacteria inside the root tissue. After inoculation of rice plantlets with PAL5 marked with the gfp plasmid pHRGFPTC, bright green fluorescent bacteria could be seen colonizing the rice root surface, mainly at the sites of lateral root emergence, at root caps and on root hairs. Conclusion:, The plasmids pHRGFPGUS and pHRGFPTC are valid tools to mark PAL5 and monitor the colonization of micropropagated sugarcane and hydroponic rice seedlings. Significance and Impact of the Study:, These tools are of use to: (i) study PAL5 mutants affected in bacteria,plant interactions, (ii) monitor plant colonization in real time and (iii) distinguish PAL5 from other bacteria during the study of mixed inoculants. [source]

Colonization process of olive tissues by Verticillium dahliae and its in planta interaction with the biocontrol root endophyte Pseudomonas fluorescens PICF7

MICROBIAL BIOTECHNOLOGY, Issue 4 2009
Pilar Prieto
Summary The colonization process of Olea europaea by the defoliating pathotype of Verticillium dahliae, and the in planta interaction with the endophytic, biocontrol strain Pseudomonas fluorescens PICF7 were determined. Differential fluorescent protein tagging was used for the simultaneous visualization of P. fluorescens PICF7 and V. dahliae in olive tissues. Olive plants were bacterized with PICF7 and then transferred to V. dahliae -infested soil. Monitoring olive colonization events by V. dahliae and its interaction with PICF7 was conducted using a non-gnotobiotic system, confocal laser scanner microscopy and tissue vibratoming sections. A yellow fluorescently tagged V. dahliae derivative (VDAT-36I) was obtained by Agrobacterium tumefaciens -mediated transformation. Isolate VDAT-36I quickly colonized olive root surface, successfully invaded root cortex and vascular tissues via macro- and micro-breakages, and progressed to the aerial parts of the plant through xylem vessel cells. Strain PICF7 used root hairs as preferred penetration site, and once established on/in root tissues, hindered pathogen colonization. For the first time using this approach, the entire colonization process of a woody plant by V. dahliae is reported. Early and localized root surface and root endophytic colonization by P. fluorescens PICF7 is needed to impair full progress of verticillium wilt epidemics in olive. [source]

The cell-cycle promoter cdc2aAt from Arabidopsis thaliana is induced in the lateral roots of the actinorhizal tree Allocasuarina verticillata during the early stages of the symbiotic interaction with Frankia

PHYSIOLOGIA PLANTARUM, Issue 3 2007
Mame Ourèye Sy
The symbiosis between the actinorhizal tree Allocasuarina verticillata and the actinomycete Frankia leads to the formation of root nodules inside which bacteria fix atmospheric nitrogen. Actinorhizal nodule organogenesis starts with the induction of cell divisions in the root cortex and in the pericycle cells opposite protoxylem poles near Frankia -infected root hairs. To study the ability of Frankia to induce progression through the cell cycle, we monitored the expression of the ,-glucuronidase (gus) gene driven by the promoter from cdc2aAt, an Arabidopsis cyclin-dependent kinase gene that displays competence for cell division, during plant growth and nodule ontogenesis. In non-symbiotic tissues, the gus gene was mainly expressed in primary and secondary meristems of roots and shoots. Auxins and cytokinins were found to induce reporter gene activity in the root system of whole plants, showing that the promoter cdc2aAt displayed the same regulation by hormones in Allocasuarina as that reported in Arabidopsis. In transgenic nodules, gus expression was found to be restricted to the phellogen. During the early stages of the interaction between Frankia and the plant root system, cdc2aAt was strongly induced in the lateral roots surrounded by hyphae of the actinomycete. Histochemical analysis of ,-glucuronidase activity revealed that cells from the pericycle opposite protoxylem poles were very deeply stained. These data indicate that upon Frankia infection, cells from the lateral roots, and notably pericycle cells that can give rise to a nodule or a root primordium, prepare to re-enter the cell cycle. [source]

Identification of QTL controlling root growth response to phosphate starvation in Arabidopsis thaliana

PLANT CELL & ENVIRONMENT, Issue 1 2006
MATTHIEU REYMOND
ABSTRACT One of the responses of plants to low sources of external phosphorus (P) is to modify root architecture. In Arabidopsis thaliana plantlets grown on low P, the primary root length (PRL) is reduced whereas lateral root growth is promoted. By using the Bay-0 × Shahdara recombinant inbred line (RIL) population, we have mapped three quantitative trait loci (QTL) involved in the root growth response to low P. The Shahdara alleles at these three QTL promote the response of the primary root to low P (i.e. root length reduction). One of these QTL, LPR1, located in a 2.8 Mb region at the top of chromosome 1, explains 52% of the variance of the PRL. We also detected a single QTL associated with primary root cell elongation in response to low P which colocalizes with LPR1. LPR1 does not seem to be involved in other typical P-starvation responses such as growth and density of root hairs, excretion of acid phosphatases, anthocyanin accumulation or the transcriptional induction of the P transporter Pht1;4. LPR1 might highlight new aspects of root growth that are revealed specifically under low P conditions. [source]

Ion transport in roots: measurement of fluxes using ion-selective microelectrodes to characterize transporter function

PLANT CELL & ENVIRONMENT, Issue 1 2001
I. A. Newman
ABSTRACT The transport of mineral ions into and out of tissues and cells is central to the life of plants. Ion transport and the plasma membrane transporters themselves have been studied using a variety of techniques. In the last 15 years, measurement of specific ion fluxes has contributed to the characterization of transport systems. Progress in molecular genetics is allowing gene identification and controlled expression of transporter molecules. However the molecular expression of transporter gene products must be characterized at the functional level. The ion-selective microelectrode technique to measure specific ion fluxes non-invasively is ideally suited to this purpose. This technique, its theory, its links with others and its application and prospects in plant science, are discussed. Ions studied include hydrogen, potassium, sodium, ammonium, calcium, chloride and nitrate. Applications discussed include: solute ion uptake by roots; gravitropism and other processes in the root cap, meristematic and elongation zones; Nod factor effect on root hairs; osmotic and salt stresses; oscillations; the effects of light and temperature. Studies have included intact roots, leaf mesophyll and other tissues, protoplasts and bacterial biofilms. A multi-ion capability of the technique will greatly assist functional genomics, particularly when coupled with imaging techniques, patch clamping and the use of suitable mutants. [source]

Early signaling through the Arabidopsis pattern recognition receptors FLS2 and EFR involves Ca2+ -associated opening of plasma membrane anion channels

THE PLANT JOURNAL, Issue 3 2010
Elena Jeworutzki
Summary The perception of microbes by plants involves highly conserved molecular signatures that are absent from the host and that are collectively referred to as microbe-associated molecular patterns (MAMPs). The Arabidopsis pattern recognition receptors FLAGELLIN-SENSING 2 (FLS2) and EF-Tu receptor (EFR) represent genetically well studied paradigms that mediate defense against bacterial pathogens. Stimulation of these receptors through their cognate ligands, bacterial flagellin or bacterial elongation factor Tu, leads to a defense response and ultimately to increased resistance. However, little is known about the early signaling pathway of these receptors. Here, we characterize this early response in situ, using an electrophysiological approach. In line with a release of negatively charged molecules, voltage recordings of microelectrode-impaled mesophyll cells and root hairs of Col-0 Arabidopsis plants revealed rapid, dose-dependent membrane potential depolarizations in response to either flg22 or elf18. Using ion-selective microelectrodes, pronounced anion currents were recorded upon application of flg22 and elf18, indicating that the signaling cascades initiated by each of the two receptors converge on the same plasma membrane ion channels. Combined calcium imaging and electrophysiological measurements revealed that the depolarization was superimposed by an increase in cytosolic calcium that was indispensable for depolarization. NADPH oxidase mutants were still depolarized upon elicitor stimulation, suggesting a reactive oxygen species-independent membrane potential response. Furthermore, electrical signaling in response to either flg22 or elf 18 critically depends on the activity of the FLS2-associated receptor-like kinase BAK1, suggesting that activation of FLS2 and EFR lead to BAK1-dependent, calcium-associated plasma membrane anion channel opening as an initial step in the pathogen defense pathway. [source]

Arabidopsis XXT5 gene encodes a putative ,-1,6-xylosyltransferase that is involved in xyloglucan biosynthesis

THE PLANT JOURNAL, Issue 1 2008
Olga A. Zabotina
Summary The function of a putative xyloglucan xylosyltransferase from Arabidopsis thaliana (At1g74380; XXT5) was studied. The XXT5 gene is expressed in all plant tissues, with higher levels of expression in roots, stems and cauline leaves. A T-DNA insertion in the XXT5 gene generates a readily visible root hair phenotype (root hairs are shorter and form bubble-like extrusions at the tip), and also causes the alteration of the main root cellular morphology. Biochemical characterization of cell wall polysaccharides isolated from xxt5 mutant seedlings demonstrated decreased xyloglucan quantity and reduced glucan backbone substitution with xylosyl residues. Immunohistochemical analyses of xxt5 plants revealed a selective decrease in some xyloglucan epitopes, whereas the distribution patterns of epitopes characteristic for other cell wall polysaccharides remained undisturbed. Transformation of xxt5 plants with a 35S::HA-XXT5 construct resulted in complementation of the morphological, biochemical and immunological phenotypes, restoring xyloglucan content and composition to wild-type levels. These data provide evidence that XXT5 is a xyloglucan ,-1,6-xylosyltransferase, and functions in the biosynthesis of xyloglucan. [source]