The structural basis for infection of root hairs of Trifolium repens by Rhizobium

1981 ◽  
Vol 59 (9) ◽  
pp. 1647-1664 ◽  
Author(s):  
Dale A. Callaham ◽  
John G. Torrey
Keyword(s):  
Trifolium Repens ◽  
Root Hair ◽  
Hydrolytic Enzymes ◽  
Root Hairs ◽  
Structural Basis ◽  
Physical Constraints ◽  
Root Hair Cell ◽  
Host Cytoplasm ◽  
Infected Root ◽  
Root Hair Infection

Root hair infection of Trifolium repens L. by Rhizobium trifolii was investigated with regard to the structural basis of infection thread origin. Most infected root hairs were shown to have in common an enclosed region at-the site of thread origin formed by specialized root hair growth or contacts. Electron micrographs of diverse infection sites showed in every case a degradation of the root hair wall at the site of thread origin within the enclosure. The thread wall is a new layer formed by apposition of material by the host cytoplasm near the penetrated wall and surrounding the break as encapsulation of the invading rhizobia. It is suggested that rhizobial enzymes provide for degradative penetration of the root hair cell wall and that localized concentrated activity of hydrolytic enzymes as well as protection from cell lysis is favored by physical constraints provided by the deformed root hair enclosures.

Root hair infection process and myconodule formation on Alnus incana by Penicillium nodositatum

1994 ◽  
Vol 72 (7) ◽  
pp. 955-962 ◽  
Author(s):  
Jeanine Sequerra ◽  
André Capellano ◽  
Monique Faure-Raynard ◽  
André Moiroud
Keyword(s):  
Root Hair ◽  
Light And Electron Microscopy ◽  
Root Hairs ◽  
Infection Process ◽  
Initial Contact ◽  
Alnus Incana ◽  
Cortical Cells ◽  
Infected Root ◽  
Root Hair Infection ◽  
Polysaccharide Matrix

Penicillium nodositatum infects the roots of alder trees and induces the formation of structures called myconodules, which are similar to young actinorhizae. Root infection of Alnus incana by P. nodositatum as well as myconodule development were studied by light and electron microscopy and observations were compared with those described for the infection by Frankia spp. We have established an obvious homology between the early steps of the infection caused by both microorganisms. The presence of the fungus near the roots induces deformation of root hairs. The infection site is probably localized in a folding of a deformed hair. As soon as hyphae penetrate into the hair, they become enclosed in a polysaccharide matrix. Initially, P. nodositatum colonizes a region near the infected root hair that may correspond to a slightly developed prenodule. Then a nodular primordium is initiated at some distance from the initial contact and the new nodular cortex is invaded by the fungus. The zone of infection is limited to the cortical cells by a barrier of tannins. Myconodules remain small and unilobed and have an outer morphology similar to that of an incompatible Frankia nodule. Key words: Alnus, myconodule formation, Penicillium, root hair infection.

scholarly journals The TOR–Auxin Connection Upstream of Root Hair Growth

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 150 ◽  
Author(s):  
Katarzyna Retzer ◽  
Wolfram Weckwerth
Keyword(s):  
Cell Fate ◽  
Root Hair ◽  
Hair Growth ◽  
Environmental Changes ◽  
Growth Control ◽  
Root Hairs ◽  
Signaling Cascades ◽  
Continuous Growth ◽  
Root Hair Cell ◽  
Root Hair Growth

Plant growth and productivity are orchestrated by a network of signaling cascades involved in balancing responses to perceived environmental changes with resource availability. Vascular plants are divided into the shoot, an aboveground organ where sugar is synthesized, and the underground located root. Continuous growth requires the generation of energy in the form of carbohydrates in the leaves upon photosynthesis and uptake of nutrients and water through root hairs. Root hair outgrowth depends on the overall condition of the plant and its energy level must be high enough to maintain root growth. TARGET OF RAPAMYCIN (TOR)-mediated signaling cascades serve as a hub to evaluate which resources are needed to respond to external stimuli and which are available to maintain proper plant adaptation. Root hair growth further requires appropriate distribution of the phytohormone auxin, which primes root hair cell fate and triggers root hair elongation. Auxin is transported in an active, directed manner by a plasma membrane located carrier. The auxin efflux carrier PIN-FORMED 2 is necessary to transport auxin to root hair cells, followed by subcellular rearrangements involved in root hair outgrowth. This review presents an overview of events upstream and downstream of PIN2 action, which are involved in root hair growth control.

Root hair deformation in the infection process of Alnus rubra

1983 ◽  
Vol 61 (11) ◽  
pp. 2863-2876 ◽  
Author(s):  
Alison M. Berry ◽  
John G. Torrey
Keyword(s):  
Root Hair ◽  
Cell Walls ◽  
Root Hairs ◽  
Infection Process ◽  
Alnus Rubra ◽  
Pseudomonas Cepacia ◽  
Developmental Studies ◽  
Experimental Conditions ◽  
Root Hair Cell ◽  
Root Hair Deformation

Structural and cell developmental studies of root hair deformation in Alnus rubra Bong. (Betulaceae) were carried out following inoculation with the soil pseudomonad Pseudomonas cepacia 85, alone or in concert with Frankia, and using axenically grown seedlings. Deformational changes can be observed in elongating root hairs within 2 h of inoculation with P. cepacia 85. These growing root hairs become branched or multilobed and highly modified from the single-tip growth of axenic root hairs. The cell walls of deformed hairs are histologically distinctive when stained with the fluorochrome acridine orange. Filtrate studies using P. cepacia 85 suggest that the deforming substance is not a low molecular weight compound. Root hair deformation and the associated wall histology are host specific in that Betula root hairs show none of these responses when grown and inoculated in the experimental conditions described. The bacterially induced changes in root hair cell walls during deformation may create a chemically and physically modified substrate for Frankia penetration, and the deformation itself may serve to entrap and enclose the filamentous organism, allowing wall dissolution and entry. Thus these events represent a complex host response as a precondition to successful nodulation.

scholarly journals Identical Accumulation and Immobilization of Sulfated and Nonsulfated Nod Factors in Host and Nonhost Root Hair Cell Walls

2003 ◽  
Vol 16 (10) ◽  
pp. 884-892 ◽  
Author(s):  
Joachim Goedhart ◽  
Jean-Jacques Bono ◽  
Ton Bisseling ◽  
Theodorus W. J. Gadella
Keyword(s):  
Hair Cell ◽  
Root Hair ◽  
Cell Walls ◽  
Root Hairs ◽  
Sharp Decrease ◽  
Biologically Active ◽  
Nod Factors ◽  
Nod Factor ◽  
Root Hair Cell ◽  
Root Hair Deformation

Nod factors are signaling molecules secreted by Rhizobium bacteria. These lipo-chitooligosaccharides (LCOs) are required for symbiosis with legumes and can elicit specific responses at subnanomolar concentrations on a compatible host. How plants perceive LCOs is unclear. In this study, using fluorescent Nod factor analogs, we investigated whether sulfated and nonsulfated Nod factors were bound and perceived differently by Medicago truncatula and Vicia sativa root hairs. The bioactivity of three novel sulfated fluorescent LCOs was tested in a root hair deformation assay on M. truncatula, showing bioactivity down to 0.1 to 1 nM. Fluorescence microscopy of plasmolyzed M. truncatula root hairs shows that sulfated fluorescent Nod factors accumulate in the cell wall of root hairs, whereas they are absent from the plasma membrane when applied at 10 nM. When the fluorescent Nod factor distribution in medium surrounding a root was studied, a sharp decrease in fluorescence close to the root hairs was observed, visualizing the remarkable capacity of root hairs to absorb Nod factors from the medium. Fluorescence correlation microscopy was used to study in detail the mobilities of sulfated and nonsulfated fluorescent Nod factors which are biologically active on M. truncatula and V. sativa, respectively. Remarkably, no difference between sulfated and nonsulfated Nod factors was observed: both hardly diffuse and strongly accumulate in root hair cell walls of both M. truncatula and V. sativa. The implications for the mode of Nod factor perception are discussed.

Callose-containing deposits in relation to root-hair infections of Alnus rubra by Frankia

1990 ◽  
Vol 68 (4) ◽  
pp. 798-802 ◽  
Author(s):  
A. M. Berry ◽  
M. E. McCully
Keyword(s):  
Electron Microscopy ◽  
Hair Cells ◽  
Root Hair ◽  
Vascular Tissue ◽  
Root Hairs ◽  
Alnus Rubra ◽  
Blue Fluorescence ◽  
Electron Dense Material ◽  
Transmission Electron ◽  
Infected Root

Light microscopy, aniline-blue fluorescence histochemistry, and transmission electron microscopy were used to elucidate the nature of localized wall deposition in infected and uninfected root hairs on nodulated roots of Alnus rubra Bong, inoculated with the nitrogen-fixing symbiont, Frankia HFPAr13. Callose-containing papillae were found only in epidermal hair cells and not in cortical or vascular tissue. At the site of successful root-hair wall penetration, transfer cell-like wall ingrowths were elaborated, but callose was not detected. At sites of arrested root-hair infections, complex deposits consisting of callose, fibrillar components, and electron-dense material surrounded the incipient hyphal infection. The cytoplasm of root hairs containing arrested infections was deteriorated compared with successfully infected root hairs.

scholarly journals The SYP123-VAMP727 SNARE complex is involved in the delivery of inner cell wall components to the root hair shank in Arabidopsis

2020 ◽  
Author(s):  
Tomoko Hirano ◽  
Kazuo Ebine ◽  
Takashi Ueda ◽  
Takumi Higaki ◽  
Takahiro Nakayama ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Root Hair ◽  
Cortical Microtubule ◽  
Root Hairs ◽  
Snare Complex ◽  
Cell Wall Components ◽  
Root Hair Cell ◽  
Wall Stiffness ◽  
Wall Components

AbstractA root hair is a long tubular protrusion from a root hair cell established via tip growth, which is accomplished by the polarized deposition of membranous and cell wall components at the root hair apex accompanied by simultaneous hardening of the shank. The polarized secretion of materials to the root hair apex is well investigated; however, little is known about the deposition of inner cell wall materials at the root hair shank. We have previously reported that phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2)/ROP10 signaling is required for the regulation of cortical microtubule construction and the deposition of inner cell wall components at the root hair shank during hardening. To unravel the alternate secretion mechanism for delivery of the inner cell wall components to root hair shank, here, we demonstrate that root hair-specific Qa-SNARE, SYP123, localizes to the subapical zone and shank of elongating root hairs in Arabidopsis. SYP123-mediated root hair elongation was inhibited by the FAB1 inhibitor YM201636, and inhibition of PtdIns(3,5)P2 production impaired the plasma membrane localization of SYP123. We also showed that SYP123 forms a SNARE complex with VAMP727 on the plasma membrane, and syp123 and vamp727 mutants exhibited lower cell wall stiffness in the root hair shank because of impaired deposition of inner cell wall components. These results indicate that SYP123/VAMP727-mediated secretion is involved in the transport of inner cell wall components for hardening of the root hair shank.

Fine structure of root hair infection leading to nodulation in the Frankia–Alnus symbiosis

1986 ◽  
Vol 64 (2) ◽  
pp. 292-305 ◽  
Author(s):  
A. M. Berry ◽  
L. McIntyre ◽  
M. E. McCully
Keyword(s):  
Cell Wall ◽  
Root Hair ◽  
Root Nodules ◽  
Structural Features ◽  
Wall Layer ◽  
Transfer Cell ◽  
Wall Formation ◽  
Root Hair Cell ◽  
Successful Infection ◽  
Root Hair Infection

Root hair infection by Frankia (Actinomycetales) is the means by which nitrogen-fixing root nodules are initiated upon the actinorhizal host, Alnus rubra. Structural details of the infectious process and the changes in host root hair cells are demonstrated at the prenodule stage for the first time using light and transmission electron microscopy. The Frankia hypha is the infective agent, extending from the rhizosphere through the root hair wall in a highly deformed region of the hair. There is no evidence of pleomorphism of the Frankia hypha. The primary wall fibrils of the root hair appear disorganized at the site of penetration. There is extensive secondary wall formation in the infected hair. At the site of penetration, root hair cell wall ingrowths occur that are structurally consistent with transfer cell wall formation. The ingrowths are continuous with the encapsulating wall layer surrounding the Frankia hypha The host cytoplasm is rich in ribosomes, secretory products, and organelles, including Golgi bodies, mitochondria, plastids, and profiles of endoplasmic reticulum. In an aborted infection sequence, some structural features of the host response to Frankia are observable, while other aspects of successful infection do not occur. Limited transfer cell wall is formed at the site of near infection. The root hair cytoplasm is senescent, however, and a callosic plug appears to surround the pathway of infection.

scholarly journals Invasion by Invitation: Rhizobial Infection in Legumes

2011 ◽  
Vol 24 (6) ◽  
pp. 631-639 ◽  
Author(s):  
Jeremy D. Murray
Keyword(s):  
Root Hair ◽  
Root Hairs ◽  
Infection Process ◽  
Nodule Development ◽  
Nod Factors ◽  
Cortical Cells ◽  
Root Cortex ◽  
Root Hair Cell ◽  
Cytoplasmic Bridges ◽  
Cytoskeletal Rearrangements

Nodulation of legume roots typically begins with rhizobia attaching to the tip of a growing root-hair cell. The attached rhizobia secrete Nod factors (NF), which are perceived by the plant. This initiates a series of preinfection events that include cytoskeletal rearrangements, curling at the root-hair tip, and formation of radially aligned cytoplasmic bridges called preinfection threads (PIT) in outer cortical cells. Within the root-hair curl, an infection pocket filled with bacteria forms, from which originates a tubular invagination of cell wall and membrane called an infection thread (IT). IT formation is coordinated with nodule development in the underlying root cortex tissues. The IT extends from the infection pocket down through the root hair and into the root cortex, where it passes through PIT and eventually reaches the nascent nodule. As the IT grows, it is colonized by rhizobia that are eventually released into cells within the nodule, where they fix nitrogen. NF can also induce cortical root hairs that appear to originate from PIT and can become infected like normal root hairs. Several genes involved in NF signaling and some of the downstream transcription factors required for infection have been characterized. More recently, several genes with direct roles in infection have been identified, some with roles in actin rearrangement and others with possible roles in protein turnover and secretion. This article provides an overview of the infection process, including the roles of NF signaling, actin, and calcium and the influence of the hormones ethylene and cytokinin.

Response of cabbage root hairs to infection by Plasmodiophora brassicae

1971 ◽  
Vol 49 (1) ◽  
pp. 41-47 ◽  
Author(s):  
P. H. Williams ◽  
Sheila J. Aist ◽  
J. R. Aist
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Root Hair ◽  
Liquid Culture ◽  
Nuclear Division ◽  
Plasmodiophora Brassicae ◽  
Root Hairs ◽  
Cellular Level ◽  
Cell Extension ◽  
Root Hair Cell

Cabbage root hairs provide a useful system for studying responses to infection by Plasmodiophora brassicae at the cellular level. Roots of cabbage seedlings grown in liquid culture were inoculated with zoospores of P. brassicae, and the effects of infection on host nucleolar development and root hair cell extension were studied. Within 18 h after the root hairs emerged from the trichoblasts the nucleoli of noninfected cells declined in diameter from 5 μ to less than 1 μ. Root hairs which became infected, whether 6 h old or 24 hold, had a nucleolar diameter ranging between 1.5 and 3 μ. The diameter of the nucleolus did not increase above 1.5–3 μ regardless of the age and number of Plasmodia within the cell. In addition to nucleolar enlargement, parasitized cells became stunted and often enlarged at their tips. Growth of Plasmodia within hair cells occurred with synchronous division of their nuclei. After penetration by the parasite there was an 18 h lag before the first nuclear division within the Plasmodia after which synchronous nuclear division occurred at about 4-h intervals.

SEM and fluorescence imaging of callose deposition in root hair tips and suspension cultures of Streptanthus tortuosus

1990 ◽  
Vol 48 (3) ◽  
pp. 698-699
Author(s):  
K.S. Walters ◽  
R.D. Sjolund ◽  
K.C. Moore
Keyword(s):  
Cell Wall ◽  
Root Hair ◽  
Cultured Cells ◽  
Root Hairs ◽  
Callus Cultures ◽  
Callose Deposition ◽  
Culture Cells ◽  
Wall Structures ◽  
Ultraviolet Illumination ◽  
Callose Formation

Callose, B-1,3-glucan, a component of cell walls, is associated with phloem sieve plates, plasmodesmata, and other cell wall structures that are formed in response to wounding or infection. Callose reacts with aniline blue to form a fluorescent complex that can be recognized in the light microscope with ultraviolet illumination. We have identified callose in cell wall protuberances that are formed spontaneously in suspension-cultured cells of S. tortuosus and in the tips of root hairs formed in sterile callus cultures of S. tortuosus. Callose deposits in root hairs are restricted to root hair tips which appear to be damaged or deformed, while normal root hair tips lack callose deposits. The callose deposits found in suspension culture cells are restricted to regions where unusual outgrowths or protuberances are formed on the cell surfaces, specifically regions that are the sites of new cell wall formation.Callose formation has been shown to be regulated by intracellular calcium levels.

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