Ontogeny of Alnus rubra – Alpova diplophloeus ectomycorrhizae. I. Light microscopy and scanning electron microscopy

1989 ◽  
Vol 67 (1) ◽  
pp. 191-200 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
L. H. Melville
Keyword(s):  
Outer Layer ◽  
Lateral Root ◽  
Lateral Roots ◽  
Root Hairs ◽  
Fungal Colonization ◽  
Alnus Rubra ◽  
Cortical Cells ◽  
Lateral Root Primordia ◽  
Hartig Net ◽  
Fungal Hyphae

Ectomycorrhizae synthesized between Alpova diplophloeus and Alnus rubra are of two morphological types: one with a mantle formed along the entire length of the lateral roots and the other, the clavate type, with the mantle confined to the apical portion of the laterals. The morphology of the mycorrhiza is dependent on the stage of lateral root elongation at the time of colonization by fungal hyphae. Clavate mycorrhizae form on lateral roots that have already elongated at the time of fungal colonization. Fungal hyphae interact with root hairs at the base of clavate mycorrhizae. Mantles of both types are fairly compact with few extramatrical hyphae. Hartig net hyphae, which branch profusely primarily in the radial direction, are confined to the epidermis and midway along the radial walls of the outer layer of cortical cells. Second-order lateral root primordia are initiated in the mature Hartig net zone. Cells in the outer layer of the cortex of mycorrhizal roots collapse during fixation, indicating the possible presence of a barrier in the cell wall blocking the ingress of fixative.

Structure and ontogeny of Betula alleghaniensis – Pisolithus tinctorius ectomycorrhizae

1990 ◽  
Vol 68 (3) ◽  
pp. 579-593 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
C. A. Ackerley ◽  
L. H. Melville
Keyword(s):  
Root Hairs ◽  
Root Surface ◽  
Pisolithus Tinctorius ◽  
Initial Contact ◽  
Broad Host Range ◽  
Betula Alleghaniensis ◽  
Cortical Cells ◽  
Structural Modifications ◽  
Hartig Net ◽  
Primary Roots

The ontogeny and ultrastructure of ectomycorrhizae synthesized between Betula alleghaniensis (yellow birch) and Pisolithus tinctorius, a broad host range fungus, were studied to determine the structural modifications in both symbionts during ectomycorrhiza establishment. A number of stages, including initial contact of hyphae with the root surface, early mantle formation, and mature mantle formation, were distinguished. Interactions between hyphae and root hairs were frequent. As a paraepidermal Hartig net developed, root epidermal cells elongated in a radial direction, but wall ingrowths were not formed. Repeated branching of Hartig net hyphae resulted in extensive fine branches and the compartmentalization of hyphal cytoplasm. Nuclei and elongated mitochondria were frequently located in the narrow cytoplasmic compartments, and [Formula: see text] thickenings developed along walls of cortical cells in primary roots.

NaCl salinity affects lateral root development in Plantago maritima

2004 ◽  
Vol 31 (8) ◽  
pp. 775 ◽  
Author(s):  
Michael Rubinigg ◽  
Julia Wenisch ◽  
J. Theo M. Elzenga ◽  
Ineke Stulen
Keyword(s):  
Growth Rate ◽  
Relative Growth Rate ◽  
Root Length ◽  
Lateral Root ◽  
Lateral Roots ◽  
Third Order ◽  
Lateral Root Primordia ◽  
Relative Growth ◽  
Length Growth ◽  
Lateral Root Length

Root growth and morphology were assessed weekly in hydroponically-grown seedlings of the halophyte Plantago maritima L. during exposure to 0, 50, 100 and 200 mm NaCl for 21 d. Relative growth rate was reduced by 25% at 200 mm NaCl. The lower NaCl treatments did not affect relative growth rates. Primary and lateral roots responded differently to NaCl. While primary-root length increased at all NaCl concentrations, total lateral-root length increased at 50 and was not affected at 100 mm but was considerably reduced at 200 mm NaCl. NaCl concentrations of 50 and 100 mm, which had no effect on relative growth rate or total lateral-root length, severely affected root branching pattern in that the number of first, second and third order laterals was reduced. At 200 mm NaCl third order laterals were not formed at all. However, mean lateral-root length was increased at all NaCl concentrations and was highest at 200 mm NaCl. We conclude that the increase in total lateral-root length in plants at 50 and 100 mm NaCl was mainly caused by increased length growth, while the decrease in total lateral-root length at 200 mm was the consequence of inhibition of lateral root primordia and / or the activation of apical meristems rather than reduced length growth.

scholarly journals Nodulation of Aeschynomene afraspera and A. indica by Photosynthetic Bradyrhizobium Sp. Strain ORS285: The Nod-Dependent Versus the Nod-Independent Symbiotic Interaction

2011 ◽  
Vol 24 (11) ◽  
pp. 1359-1371 ◽  
Author(s):  
Katia Bonaldi ◽  
Daniel Gargani ◽  
Yves Prin ◽  
Joel Fardoux ◽  
Djamel Gully ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Lateral Roots ◽  
Root Hairs ◽  
Infection Process ◽  
Cortical Cells ◽  
Symbiotic Interaction ◽  
Root Cortex ◽  
Bradyrhizobium Sp ◽  
Infected Cells ◽  
Green Fluorescent

Here, we present a comparative analysis of the nodulation processes of Aeschynomene afraspera and A. indica that differ in their requirement for Nod factors (NF) to initiate symbiosis with photosynthetic bradyrhizobia. The infection process and nodule organogenesis was examined using the green fluorescent protein–labeled Bradyrhizobium sp. strain ORS285 able to nodulate both species. In A. indica, when the NF-independent strategy is used, bacteria penetrated the root intercellularly between axillary root hairs and invaded the subepidermal cortical cells by invagination of the host cell wall. Whereas the first infected cortical cells collapsed, the infected ones immediately beneath kept their integrity and divided repeatedly to form the nodule. In A. afraspera, when the NF-dependent strategy is used, bacteria entered the plant through epidermal fissures generated by the emergence of lateral roots and spread deeper intercellularly in the root cortex, infecting some cortical cells during their progression. Whereas the infected cells of the lower cortical layers divided rapidly to form the nodule, the infected cells of the upper layers gave rise to an outgrowth in which the bacteria remained enclosed in large tubular structures. Together, two distinct modes of infection and nodule organogenesis coexist in Aeschynomene legumes, each displaying original features.

scholarly journals A single cell view of the transcriptome during lateral root initiation in Arabidopsis thaliana

2020 ◽  
Author(s):  
Hardik P. Gala ◽  
Amy Lanctot ◽  
Ken Jean-Baptiste ◽  
Sarah Guiziou ◽  
Jonah C. Chu ◽  
...  
Keyword(s):  
Single Cell ◽  
Root Development ◽  
Lateral Root ◽  
Lateral Roots ◽  
Primary Root ◽  
Root Initiation ◽  
Lateral Root Primordia ◽  
Lateral Root Development ◽  
Lateral Root Initiation ◽  
Molecular Events

AbstractRoot architecture is a major determinant of fitness, and is under constant modification in response to favorable and unfavorable environmental stimuli. Beyond impacts on the primary root, the environment can alter the position, spacing, density and length of secondary or lateral roots. Lateral root development is among the best-studied examples of plant organogenesis, yet there are still many unanswered questions about its earliest steps. Among the challenges faced in capturing these first molecular events is the fact that this process occurs in a small number of cells with unpredictable timing. Single-cell sequencing methods afford the opportunity to isolate the specific transcriptional changes occurring in cells undergoing this fate transition. Using this approach, we successfully captured the transcriptomes of initiating lateral root primordia, and discovered many previously unreported upregulated genes associated with this process. We developed a method to selectively repress target gene transcription in the xylem pole pericycle cells where lateral roots originate, and demonstrated that expression of several of these targets was required for normal root development. We also discovered novel subpopulations of cells in the pericycle and endodermal cell files that respond to lateral root initiation, highlighting the coordination across cell files required for this fate transition.One sentence summarySingle cell RNA sequencing reveals new molecular details about lateral root initiation, including the transcriptional impacts of the primordia on bordering cells.

Host microtubules in the Hartig net region of ectomycorrhizas, ectendomycorrhizas, and monotropoid mycorrhizas

2004 ◽  
Vol 82 (7) ◽  
pp. 938-946 ◽  
Author(s):  
Yukari Kuga-Uetake ◽  
Melissa Purich ◽  
Hugues B Massicotte ◽  
R. Larry Peterson
Keyword(s):  
Pinus Banksiana ◽  
Structural Changes ◽  
Close Association ◽  
Confocal Scanning Laser Microscopy ◽  
Fungal Colonization ◽  
Cortical Cells ◽  
Root Cells ◽  
Hartig Net ◽  
Confocal Scanning Laser ◽  
Wilcoxina Mikolae

Various categories of mycorrhizas are recognized primarily by the structural changes that occur between fungi and roots. In all mycorrhiza categories, cytological modifications of root cells accompany the establishment of the functional symbiosis, and among these are alterations in the organization of the cytoskeleton. Using immuno labelling combined with confocal scanning laser microscopy, this study documents changes in microtubules (MTs) in root cells of ectendomycorrhizas and monotropoid mycorrhizas; in addition, ectomycorrhizas were reinvestigated to determine the effect of fungal colonization on host root cells. In Pinus banksiana L. – Laccaria bicolor (Maire) Orton ectomycorrhizas, MTs were present in epidermal and cortical cells adjacent to the Hartig net. The remaining cortical MTs had a different organization when compared with those of cortical cells of control roots. MTs were present in Hartig net hyphae. In ectendomycorrhizas formed when roots of P. banksiana were colonized by the ascomycete, Wilcoxina mikolae var. mikolae Yang & Korf, MTs were present adjacent to intracellular hyphae and host nuclei, but few cortical MTs were present. MTs were present within Hartig net and intracellular hyphae. In field-collected roots of Monotropa uniflora L., MTs were associated with fungal pegs, intracellular extensions of inner mantle hyphae within epidermal cells. The close association between MTs and fungal pegs may be related to the formation of the highly branched host-derived wall that envelops each fungal peg. The development of exchange interfaces in the three systems studied involve changes in the organization of microtubules.Key words: cytoskeleton, microtubules, Hartig net, mycorrhizas, immunolocalization, confocal microscopy.

Analysis of lateral root growth in Arabidopsis in response to physiologically active auxin analogues

2010 ◽  
Vol 58 (1) ◽  
pp. 1-10 ◽  
Author(s):  
L. Novickienė ◽  
V. Gavelienė ◽  
L. Miliuvienė ◽  
D. Kazlauskienė ◽  
L. Pakalniškytė
Keyword(s):  
Lateral Root ◽  
Apical Meristem ◽  
Lateral Roots ◽  
Root System Architecture ◽  
Test Plant ◽  
Wild Type ◽  
Root Primordia ◽  
Lateral Root Primordia ◽  
Primary Roots ◽  
The Impact

The aim of this work was to investigate the formation and development of lateral roots in model trials on Arabidopsis thaliana L. Heynh wild type (Col-0), the alf4-1 mutant and its allele by applying the physiologically active auxin analogues IBA, IAA, TA-12 and TA-14.Differences were observed between the alf4-1 mutant and its allele phenotype in the formation of lateral roots. The application of auxin analogues was unable to restore the formation of lateral roots in the alf4-1 mutant. In some cases, under the impact of IBA (1 μM), a cluster of xylem cells was activated in the pericycle of the primary roots and lateral root primordia were formed. The auxin analogues induced the growth of primary roots in the alf4-1 allele and the formation and growth of lateral roots. The impact of IBA (1 μM), TA-12 (1 mM) and IAA (1 μM) was particularly evident. The intense formation of lateral roots under the impact of IBA and TA-12 could be related with the ability of these compounds to intensify mitotic activity in the apical meristem cells of the lateral roots. New data were obtained, showing that IBA and other physiologically active auxin analogues can modify the root system architecture of the test-plant Arabidopsis .

scholarly journals Flavonols modulate lateral root emergence by scavenging reactive oxygen species in Arabidopsis thaliana

2020 ◽  
pp. jbc.RA120.014543
Author(s):  
Jordan M. Chapman ◽  
Gloria K. Muday
Keyword(s):  
Arabidopsis Thaliana ◽  
Root Development ◽  
Lateral Root ◽  
Lateral Roots ◽  
Negative Regulator ◽  
Wild Type ◽  
Root Primordia ◽  
Lateral Root Primordia ◽  
Lateral Root Development ◽  
Genes Encoding

Flavonoids are a class of specialized metabolites with subclasses including flavonols and anthocyanins, which have unique properties as antioxidants. Flavonoids modulate plant development, but whether and how they impact lateral root development is unclear. We examined potential roles for flavonols in this process using Arabidopsis thaliana mutants with defects in genes encoding key enzymes in flavonoid biosynthesis. We observed the tt4 and fls1 mutants, which produce no flavonols, have increased lateral root emergence. The tt4 root phenotype was reversed by genetic and chemical complementation. To more specifically define the flavonoids involved, we tested an array of flavonoid biosynthetic mutants, eliminating roles for anthocyanins and the flavonols quercetin and isorhamnetin in modulating root development. Instead, two tt7 mutant alleles, with defects in a branchpoint enzyme blocking quercetin biosynthesis, formed reduced numbers of lateral roots, and tt7-2 had elevated levels of kaempferol. Using a flavonol-specific dye, we observed that in the tt7-2 mutant, kaempferol accumulated within lateral root primordia at higher levels than wild-type. These data are consistent with kaempferol, or downstream derivatives, acting as a negative regulator of lateral root emergence. We examined ROS accumulation using ROS-responsive probes and found reduced fluorescence of a superoxide-selective probe within the primordia of tt7-2 compared to wild type, but not in the tt4 mutant, consistent with opposite effects of these mutants on lateral root emergence. These results support a model in which increased level of kaempferol in the lateral root primordia of tt7-2 reduces superoxide concentration and ROS-stimulated lateral root emergence.

scholarly journals Carbohydrate-Binding Module of a Rice Endo-β-1,4-glycanase, OsCel9A , Expressed in Auxin-Induced Lateral Root Primordia, is Post-Translationally Truncated

2006 ◽  
Vol 47 (11) ◽  
pp. 1555-1571 ◽  
Author(s):  
Kouki Yoshida ◽  
Nobuyuki Imaizumi ◽  
Satoshi Kaneko ◽  
Yasushi Kawagoe ◽  
Akemi Tagiri ◽  
...  
Keyword(s):  
Lateral Root ◽  
Time Course ◽  
Oryza Sativa L ◽  
Lateral Roots ◽  
Organ Specificity ◽  
Glycoside Hydrolase Family ◽  
Carbohydrate Binding ◽  
Carbohydrate Binding Module ◽  
Root Primordia ◽  
Lateral Root Primordia

Abstract We report the cloning of a glycoside hydrolase family (GHF) 9 gene of rice ( Oryza sativa L. cv. Sasanishiki), OsCel9A , corresponding to the auxin-induced 51 kDa endo-1,4-β-glucanase (EGase). This enzyme reveals a broad substrate specificity with respect to sugar backbones (glucose and xylose) in β-1,4-glycans of type II cell wall. OsCel9A encodes a 640 amino acid polypeptide and is an ortholog of TomCel8 , a tomato EGase containing a carbohydrate-binding module (CBM) 2 sequence at its C-terminus. The expression of four rice EGase genes including OsCel9A showed different patterns of organ specificity and responses to auxin. OsCel9A was preferentially expressed during the initiation of lateral roots or subcultured root calli, but was hardly expressed during auxin-induced coleoptile elongation or in seed calli, in contrast to OsCel9D , a KORRIGAN ( KOR ) homolog. In situ localization of OsCel9A transcripts demonstrated that its expression was specifically up-regulated in lateral root primordia (LRP). Northern blotting analysis showed the presence of a single product of OsCel9A . In contrast, both mass spectrometric analyses of peptide fragments from purified 51 kDa EGase proteins and immunogel blot analysis of EGase proteins in root extracts using two antibodies against internal peptide sequences of OsCel9A revealed that the entire CBM2 region was post-translationally truncated from the 67 kDa nascent protein to generate 51 kDa EGase isoforms. Analyses of auxin concentration and time course dependence of accumulation of two EGase isoforms suggested that the translation and post-translational CBM2 truncation of the OsCel9A gene may participate in lateral root development.

scholarly journals Auxin: at the root of nodule development?

2008 ◽  
Vol 35 (8) ◽  
pp. 651 ◽  
Author(s):  
Ulrike Mathesius
Keyword(s):  
Lateral Root ◽  
De Novo ◽  
Root Nodules ◽  
Lateral Roots ◽  
Nodule Development ◽  
Nodule Formation ◽  
Cortical Cells ◽  
Lateral Root Development ◽  
Organ Differentiation ◽  
Development And Differentiation

Root nodules are formed as a result of an orchestrated exchange of chemical signals between symbiotic nitrogen fixing bacteria and certain plants. In plants that form nodules in symbiosis with actinorhizal bacteria, nodules are derived from lateral roots. In most legumes, nodules are formed de novo from pericycle and cortical cells that are re-stimulated for division and differentiation by rhizobia. The ability of plants to nodulate has only evolved recently and it has, therefore, been suggested that nodule development is likely to have co-opted existing mechanisms for development and differentiation from lateral root formation. Auxin is an important regulator of cell division and differentiation, and changes in auxin accumulation and transport are essential for lateral root development. There is growing evidence that rhizobia alter the root auxin balance as a prerequisite for nodule formation, and that nodule numbers are regulated by shoot-to-root auxin transport. Whereas auxin requirements appear to be similar for lateral root and nodule primordium activation and organ differentiation, the major difference between the two developmental programs lies in the specification of founder cells. It is suggested that differing ratios of auxin and cytokinin are likely to specify the precursors of the different root organs.

Prenodule formation and primary nodule development in roots of Comptonia (Myricaceae)

1977 ◽  
Vol 55 (17) ◽  
pp. 2306-2318 ◽  
Author(s):  
Dale Callaham ◽  
John G. Torrey
Keyword(s):  
Root Hair ◽  
Lateral Root ◽  
Lateral Roots ◽  
Cortical Cell ◽  
Host Cells ◽  
Nodule Development ◽  
Nodule Formation ◽  
Cortical Cells ◽  
Lateral Root Primordium ◽  
Root Primordium

Seedlings of the sweet fern, Comptonia peregrina (L.) Coult., grown aeroponically, were inoculated with a nodule suspension to allow infection by the actinomycete-like organism which causes nodule formation. Roots with early stages of infection and nodule initiation were fixed, embedded in resin, sectioned, and examined. Infection is infrequent in Comptonia with only a few nodules per seedling root system. Infection via root hair invasion causes the retention of the curled and deformed root hair in an intensely cytoplasmic state with ramification of multiple filamentous strands of the endophyte. A limited cortical proliferation occurs in response to the infection forming the prenodule; endophyte filaments grow radially inward from the base of the infected epidermal root hair and invade a portion of the prenodular cells resulting in their hypertrophy. Distal and proximal to the prenodule site, a number of primary nodule primordia are initiated, varying from a few up to a dozen or more. These primordia appear to develop more or less simultaneously under the stimulus of the invading endophyte; they are like lateral roots in their site of origin, occurring largely opposite the protoxylem poles and involving pericyclic and endodermal cell proliferation. They differ in that the cortical cells external to each primordium are stimulated to undergo divisions and these cortical cell derivatives are incorporated into the developing primordium. The endophyte enters the cortical tissues of the lateral root on which the prenodule has formed and then invades proximal and distal to the infection site, progressing into the cortical tissues of each of the developing nodule primordia. A cork-like layer develops on the original lateral root in areas not occupied by primordia by initiation of subepidermal cell divisions and wall thickening. Normal lateral root primordium formation occurs in the pericycle opposite the protoxylem poles and involves cellular derivatives of the pericycle and endodermis but no cortical cells, which instead are crushed and displaced by the lateral root primordium as it develops. Nodule formation clearly involves complex chemical interactions, which remain for further study, between the host cells and the invading endophyte.

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