Anatomical analysis of the development and distribution of Rhizobium infections in soybean roots

1984 ◽  
Vol 62 (11) ◽  
pp. 2375-2384 ◽  
Author(s):  
Harry E. Calvert ◽  
Mark K. Pence ◽  
Margaret Pierce ◽  
Nasir S. A. Malik ◽  
Wolfgang D. Bauer
Keyword(s):  
Cortical Cell ◽  
Root Hairs ◽  
Rhizobium Japonicum ◽  
Nodule Development ◽  
Root Hair Development ◽  
Infection Threads ◽  
Developmental Scale ◽  
Thread Formation ◽  
Glycine Max L ◽  
Hair Development

Roots of young soybean (Glycine max (L.) Merr.) seedlings inoculated with Rhizobium japonicum Kirchner USDA 110 ARS were examined in serial sections by light microscopy to ascertain the extent of infection. The location of each infection site was established in relation to the zones of root and root hair development at the time of inoculation. Each infection locus was classified as to its relative state of differentiation using a developmental scale encompassing the first 10 days of nodule development. Both the initiation and maturation of Rhizobium infections were found to be governed by the acropetal development of host root hairs. Regions of the root where mature root hairs were present at the time of inoculation were not susceptible to Rhizobium infection. Infections developed most frequently in root hairs which emerged shortly after inoculation. Many infections formed on the root but relatively few developed into nodules. Most infection loci which formed infection threads stopped developing at stages prior to meristem formation. A high proportion of the infection loci were pseudoinfections, i.e., localized areas of cortical cell division without infection thread formation. The maturation of infections in younger regions of the root was suppressed by prior exposure of older regions of the root to rhizobia. Development was suppressed at stages after meristem formation but before nodule emergence.

Early events in the infection of soybean by Rhizobium japonicum. Time course and cytology of the initial infection process

1982 ◽  
Vol 60 (2) ◽  
pp. 152-161 ◽  
Author(s):  
B. Gillian Turgeon ◽  
Wolfgang D. Bauer
Keyword(s):  
Root Hair ◽  
Time Course ◽  
Cortical Cell ◽  
Root Hairs ◽  
Infection Process ◽  
Infection Thread ◽  
Rhizobium Japonicum ◽  
Outer Cortex ◽  
Light Microscope Level ◽  
Infection Threads

The time course of early infection events in Glycine max following inoculation with Rhizobium japonicum is described. Bacteria became attached to epidermal cells and root hairs within minutes of inoculation. Marked root hair curling occurred within 12 h. Infection thread formation was visible at the light microscope level of resolution about 24 h after inoculation. Infections were observed in short, tightly curled root hairs. These root hairs had not yet emerged at the time of inoculation. Infection threads appeared to originate in pockets formed by contact of the cell wall of the curled root hair with itself. Infection threads in the hairs were multiple and (or) branched. By 48 h, the infection thread(s) had progressed to the base of the root hair but had not yet penetrated into the cortex. Increases in cortical cell cytoplasm and in mitotic division occurred in advance of the penetrating infection thread. A nodule meristem developed in the outer cortex next to the infected root hair by 4 days and was accompanied by cell division across the cortex.

scholarly journals 3,4-dehydro-L-proline Induces Programmed Cell Death in the Roots of Brachypodium distachyon

2021 ◽  
Vol 22 (14) ◽  
pp. 7548
Author(s):  
Artur Pinski ◽  
Alexander Betekhtin ◽  
Jolanta Kwasniewska ◽  
Lukasz Chajec ◽  
Elzbieta Wolny ◽  
...  
Keyword(s):  
Cell Death ◽  
Brachypodium Distachyon ◽  
Root Hairs ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Cell Wall Proteins ◽  
Root Epidermis ◽  
Root Hair Development ◽  
Transmission Electron ◽  
Hair Development

As cell wall proteins, the hydroxyproline-rich glycoproteins (HRGPs) take part in plant growth and various developmental processes. To fulfil their functions, HRGPs, extensins (EXTs) in particular, undergo the hydroxylation of proline by the prolyl-4-hydroxylases. The activity of these enzymes can be inhibited with 3,4-dehydro-L-proline (3,4-DHP), which enables its application to reveal the functions of the HRGPs. Thus, to study the involvement of HRGPs in the development of root hairs and roots, we treated seedlings of Brachypodium distachyon with 250 µM, 500 µM, and 750 µM of 3,4-DHP. The histological observations showed that the root epidermis cells and the cortex cells beneath them ruptured. The immunostaining experiments using the JIM20 antibody, which recognizes the EXT epitopes, demonstrated the higher abundance of this epitope in the control compared to the treated samples. The transmission electron microscopy analyses revealed morphological and ultrastructural features that are typical for the vacuolar-type of cell death. Using the TUNEL test (terminal deoxynucleotidyl transferase dUTP nick end labelling), we showed an increase in the number of nuclei with damaged DNA in the roots that had been treated with 3,4-DHP compared to the control. Finally, an analysis of two metacaspases’ gene activity revealed an increase in their expression in the treated roots. Altogether, our results show that inhibiting the prolyl-4-hydroxylases with 3,4-DHP results in a vacuolar-type of cell death in roots, thereby highlighting the important role of HRGPs in root hair development and root growth.

Infection thread formation as a basis of nodulation specificity in Rhizobium – strawberry clover associations

1969 ◽  
Vol 15 (10) ◽  
pp. 1133-1136 ◽  
Author(s):  
Diana Li ◽  
D. H. Hubbell
Keyword(s):  
Characteristic Root ◽  
Root Hairs ◽  
Infection Thread ◽  
Root Hair Deformation ◽  
Infection Threads ◽  
Specific Substance ◽  
Thread Formation ◽  
Nodulation Specificity ◽  
Infection Thread Formation

The basis for determination of nodulating specificity in Rhizobium–clover associations was investigated. Thirteen strains of rhizobia from eight different cross-inoculation groups were used to inoculate aseptically grown strawberry clover seedlings in slide culture. Microscopic observation revealed that each strain produced characteristic root hair deformation but infection threads and nodules were observed only in the homologous combination. It is concluded that, in rhizobia–clover combinations which nodulate via infection threads, specificity is determined at or before infection thread initiation. Observations of other workers that rhizobia produce a strain-specific substance affecting growth and morphology of legume root hairs were confirmed by results of this study.

scholarly journals Morphogenesis of root nodules in white clover. II. The effect of mutation in genes nod IJ of the microsymbiont upon the nodule structure

2014 ◽  
Vol 67 (1) ◽  
pp. 5-22
Author(s):  
Barbara Łotocka ◽  
Joanna Kopcińska ◽  
Władysław Golinowski
Keyword(s):  
White Clover ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Single Cells ◽  
Wild Strain ◽  
Root Hairs ◽  
Nodule Development ◽  
Wild Type ◽  
Delayed Reaction ◽  
Infection Threads

Morphogenesis of ineffective root nodules initiated on the roots of white clover 'Astra' by the <em>Rhizobium leguminosarum</em> biovar. <em>trifolii</em> strains ANU261 (Tn5 insertion in nod 1 gene) and ANU262 (Tn5 insertion in nod J gene) was investigated. Following changes were observed, as compared to the wild-type nodulation: the exaggerated, not delayed reaction of root hairs; the delay in nodulation with the number of nodules the same as in plants inoculated with a wild strain; the formation and organization of the nodule primordium not changed in comparison with the wild-type nodules; infection threads abnormally branched and diffusing with bacteria deprived of light zone and enriched with storage material; infected cells of bacteroidal tissue abnormally strongly osmiophilic and only slightly vacuolated; symbiosomes with very narrowed peribacteroidal space, subject to premature degradation; abnormal accumulation of starch in the nodule tissues; nodule development blocked at the stage of laterally situated meristem and single nodule bundle; inhibition of divisions in the meristem and vacuolation of its cells; the appearance of single cells with colonies of saprophytic rhizobia embedded in the fibrillar matrix in the old, degraded regions of the bacteroidal tissue.

scholarly journals Root hair specification and its growth in response to nutrients

2021 ◽  
Vol 49 (2) ◽  
pp. 12258
Author(s):  
Xian HUANG ◽  
Tianzhi GONG ◽  
Mei LI ◽  
Cenghong HU ◽  
Dejian ZHANG ◽  
...  
Keyword(s):  
Root Hair ◽  
Reverse Genetics ◽  
Current Knowledge ◽  
Plant Root ◽  
Root Hairs ◽  
Root Surface ◽  
Root Surface Area ◽  
Root Hair Development ◽  
Hair Development ◽  
Calcium Iron

Plant root hairs are cylindrical tubular projections from root epidermal cells. They increase the root surface area, which is important for the acquisition of water and nutrients, microbe interactions, and plant anchorage. The root hair specification, the effect of root hairs on nutrient acquisition and the mechanisms of nutrients (calcium, iron, magnesium, nitrogen, phosphorus, and potassium) that affect root hair development and growth were reviewed. The gene regulatory network on root hair specification in the plant kingdom was highlighted. More work is needed to clone the genes of additional root hair mutants and elucidate their roles, as well as undertaking reverse genetics and mutant complementation studies to add to the current knowledge of the signaling networks, which are involved in root hair development and growth regulated by nutrients.

scholarly journals Root hairs are the most important root trait for rhizosheath formation of barley (Hordeum vulgare), maize (Zea mays) and Lotus japonicus (Gifu)

2021 ◽  
Author(s):  
Emma Burak ◽  
John N Quinton ◽  
Ian C Dodd
Keyword(s):  
Zea Mays ◽  
Hordeum Vulgare ◽  
Root Hair ◽  
Root Length ◽  
Root Exudate ◽  
Lotus Japonicus ◽  
Root Hairs ◽  
Root Hair Development ◽  
Maize Genotypes ◽  
Hair Development

Abstract Background and Aims Rhizosheaths are defined as the soil adhering to the root system after it is extracted from the ground. Root hairs and mucilage (root exudates) are key root traits involved in rhizosheath formation, but to better understand the mechanisms involved their relative contributions should be distinguished. Methods The ability of three species [barley (Hordeum vulgare), maize (Zea mays) and Lotus japonicus (Gifu)] to form a rhizosheath in a sandy loam soil was compared with that of their root-hairless mutants [bald root barley (brb), maize root hairless 3 (rth3) and root hairless 1 (Ljrhl1)]. Root hair traits (length and density) of wild-type (WT) barley and maize were compared along with exudate adhesiveness of both barley and maize genotypes. Furthermore, root hair traits and exudate adhesiveness from different root types (axile versus lateral) were compared within the cereal species. Key Results Per unit root length, rhizosheath size diminished in the order of barley &gt; L. japonicus &gt; maize in WT plants. Root hairs significantly increased rhizosheath formation of all species (3.9-, 3.2- and 1.8-fold for barley, L. japonicus and maize, respectively) but there was no consistent genotypic effect on exudate adhesiveness in the cereals. While brb exudates were more and rth3 exudates were less adhesive than their respective WTs, maize rth3 bound more soil than barley brb. Although both maize genotypes produced significantly more adhesive exudate than the barley genotypes, root hair development of WT barley was more extensive than that of WT maize. Thus, the greater density of longer root hairs in WT barley bound more soil than WT maize. Root type did not seem to affect rhizosheath formation, unless these types differed in root length. Conclusions When root hairs were present, greater root hair development better facilitated rhizosheath formation than root exudate adhesiveness. However, when root hairs were absent root exudate adhesiveness was a more dominant trait.

EIN3 and RSL4 interfere with an MYB–bHLH–WD40 complex to mediate ethylene-induced ectopic root hair formation in Arabidopsis

2021 ◽  
Vol 118 (51) ◽  
pp. e2110004118
Author(s):  
Yuping Qiu ◽  
Ran Tao ◽  
Ying Feng ◽  
Zhina Xiao ◽  
Dan Zhang ◽  
...  
Keyword(s):  
Root Hair ◽  
Molecular Mechanisms ◽  
Protein Complexes ◽  
Root Hairs ◽  
Elongation Factor ◽  
Root Hair Development ◽  
Root Hair Formation ◽  
Hair Development ◽  
Transcriptional Complex ◽  
Hair Formation

The alternating cell specifications of root epidermis to form hair cells or nonhair cells in Arabidopsis are determined by the expression level of GL2, which is activated by an MYB–bHLH–WD40 (WER–GL3–TTG1) transcriptional complex. The phytohormone ethylene (ET) has a unique effect of inducing N-position epidermal cells to form root hairs. However, the molecular mechanisms underlying ET-induced ectopic root hair development remain enigmatic. Here, we show that ET promotes ectopic root hair formation through down-regulation of GL2 expression. ET-activated transcription factors EIN3 and its homolog EIL1 mediate this regulation. Molecular and biochemical analyses further revealed that EIN3 physically interacts with TTG1 and interferes with the interaction between TTG1 and GL3, resulting in reduced activation of GL2 by the WER–GL3–TTG1 complex. Furthermore, we found through genetic analysis that the master regulator of root hair elongation, RSL4, which is directly activated by EIN3, also participates in ET-induced ectopic root hair development. RSL4 negatively regulates the expression of GL2, likely through a mechanism similar to that of EIN3. Therefore, our work reveals that EIN3 may inhibit gene expression by affecting the formation of transcription-activating protein complexes and suggests an unexpected mutual inhibition between the hair elongation factor, RSL4, and the hair specification factor, GL2. Overall, this study provides a molecular framework for the integration of ET signaling and intrinsic root hair development pathway in modulating root epidermal cell specification.

scholarly journals Nod Factor Perception During Infection Thread Growth Fine-Tunes Nodulation

2007 ◽  
Vol 20 (2) ◽  
pp. 129-137 ◽  
Author(s):  
Jeroen Den Herder ◽  
Celine Vanhee ◽  
Riet De Rycke ◽  
Viviana Corich ◽  
Marcelle Holsters ◽  
...  
Keyword(s):  
Light And Electron Microscopy ◽  
Cortical Cell ◽  
Root Hairs ◽  
Infection Thread ◽  
Bacterial Invasion ◽  
Nodule Formation ◽  
Nodulation Factors ◽  
Polysaccharide Synthesis ◽  
Infection Threads ◽  
Surface Polysaccharide

Bacterial nodulation factors (NFs) are essential signaling molecules for the initiation of a nitrogen-fixing symbiosis in legumes. NFs are perceived by the plant and trigger both local and distant responses, such as curling of root hairs and cortical cell divisions. In addition to their requirement at the start, NFs are produced by bacteria that reside within infection threads. To analyze the role of NFs at later infection stages, several phases of nodulation were studied by detailed light and electron microscopy after coinoculation of adventitious root primordia of Sesbania rostrata with a mixture of Azorhizobium caulinodans mutants ORS571-V44 and ORS571-X15. These mutants are deficient in NF production or surface polysaccharide synthesis, respectively, but they can complement each other, resulting in functional nodules occupied by ORS571-V44. The lack of NFs within the infection threads was confirmed by the absence of expression of an early NF-induced marker, leghemoglobin 6 of S. rostrata. NF production within the infection threads is shown to be necessary for proper infection thread growth and for synchronization of nodule formation with bacterial invasion. However, local production of NFs by bacteria that are taken up by the plant cells at the stage of bacteroid formation is not required for correct symbiosome development.

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