Physiological and morphological aspects of interactions between Rhizobium meliloti and alfalfa (Medicago sativa) in association with Azospirillum brasilense

1993 ◽  
Vol 39 (6) ◽  
pp. 610-615 ◽  
Author(s):  
R. Itzigsohn ◽  
Y. Kapulnik ◽  
Y. Okon ◽  
A. Dovrat
Keyword(s):  
Medicago Sativa ◽  
Rhizobium Meliloti ◽  
Combined Treatment ◽  
Root Hairs ◽  
Background Level ◽  
Root Surface ◽  
Root Surface Area ◽  
Main Root ◽  
Nodule Number ◽  
Infection Threads

In a 50-L pot experiment with Medicago sativa grown under nonsterile conditions, a combined treatment of Azospirillum and Rhizobium was measured against soil inoculated with Rhizobium or Azospirillum alone or a control with a low background level of autochthonous rhizobia. The combined treatment significantly increased the shoot length and weight at 6 weeks and the regrowth shoot weight at 14 weeks when compared with the treatment with Rhizobium alone. In 1.5-L pots in which gnotobiotic conditions were maintained, the combined treatment led to more nodules on the main root at intermediate Rhizobium concentrations, and a greater root surface area at intermediate and high Rhizobium concentrations after 2 weeks but not after 4 weeks. In pouch-grown seedlings, plants were inoculated with either Rhizobium alone or in combination with Azospirillum or applied together with a flavonoid, luteolin (a nodulation gene inducer), or with a cytokinin, benzyl adenine. Luteolin had similar effects to those of Azospirillum in increasing the main root nodule number and the total nodule number. With Fahraeus slides, a significant increase was observed in the number of root hairs and the root diameter in the presence of Azospirillum as compared with the control and Rhizobium alone. There was no increase in the total number of infection threads; however, the combined treatment caused a significant decrease in the percentage of infected root hairs.Key words: Rhizobium, Azospirillum, Medicago, flavonoid, inoculation.

Nodule morphogenesis: the early infection of Alfalfa (Medicago sativa) root hairs by Rhizobium meliloti

1989 ◽  
Vol 67 (10) ◽  
pp. 3108-3122 ◽  
Author(s):  
Susan M. Wood ◽  
William Newcomb
Keyword(s):  
Medicago Sativa ◽  
Root Hair ◽  
Rhizobium Meliloti ◽  
Root Hairs ◽  
Growth Period ◽  
Active Phase ◽  
Infection Threads ◽  
Thread Formation ◽  
Time Of Infection ◽  
Meliloti Strain

The growth and development of alfalfa (Medicago sativa) cv. Saranac root hairs and their infection by Rhizobium meliloti strain 102F51 was studied with Smith's interference contrast optics. Uninoculated root hairs grew and matured over a 10-h growth period. The nucleus migrated from a position opposite that of root-hair protrusion at initiation to the base of the root-hair protrusion, then into the growing root hair during the most active phase. When growth was nearly complete, the nucleus assumed a position near the base of the vacuolate root hair. If root hairs were inoculated during the first 2 h of growth after initiation, either "Shepherd's crooks" or root hairs deformed into a tight curl as the tip developed. Some of these Shepherd's rooks later demonstrated typical infection-thread formation. Root hairs that were inoculated between 4 and 6 h after root-hair initiation demonstrated branched growth, with the branch forming opposite the position of the nucleus at the time of infection. Infection threads occasionally formed in either the side branches or tip branches. Root hairs that were older than 6 h at the time of inoculation formed a variety of growth deformations, including ballooning, and elongate, spatulate, spiralling, or intertwined growth. Infections in this population of root hairs were rare.

scholarly journals H2O2 Is Required for Optimal Establishment of the Medicago sativa/Sinorhizobium meliloti Symbiosis

2007 ◽  
Vol 189 (23) ◽  
pp. 8741-8745 ◽  
Author(s):  
Alexandre Jamet ◽  
Karine Mandon ◽  
Alain Puppo ◽  
Didier Hérouart
Keyword(s):  
Medicago Sativa ◽  
Plant Cell ◽  
Sinorhizobium Meliloti ◽  
Root Hairs ◽  
Symbiotic Interaction ◽  
Infection Threads ◽  
Cell Layers

ABSTRACT The symbiotic interaction between Medicago sativa and Sinorhizobium meliloti RmkatB ++ overexpressing the housekeeping catalase katB is delayed, and this delay is combined with an enlargement of infection threads. This result provides evidence that H2O2 is required for optimal progression of infection threads through the root hairs and plant cell layers.

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 Morphology of root nodules and nodule-like structures formed by Rhizobium and Agrobacterium strains containing a Rhizobium meliloti megaplasmid.

1983 ◽  
Vol 97 (3) ◽  
pp. 787-794 ◽  
Author(s):  
C H Wong ◽  
C E Pankhurst ◽  
A Kondorosi ◽  
W J Broughton
Keyword(s):  
Normal Development ◽  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Root Hairs ◽  
Host Cells ◽  
Donor Strain ◽  
Intercellular Spaces ◽  
Infection Threads ◽  
Infected Cells ◽  
Rhizobium Sp

We examined expression of the megaplasmid pRme41b of Rhizobium meliloti in two different Rhizobium sp. Strains and in Agrobacterium tumefaciens. Transfer of pRme41b into these bacteria was facilitated by insertion of a recombinant plasmid coding for mobilization functions of RP4 into the nif region (Kondorosi, A., E. Kondorosi, C.E. Pankhurst, W. J. Broughton, and Z. Banfalvi, 1982, Mol. Gen. Genet., 188:433-439). In all cases, transconjugants formed nodule-like structures on the roots of Medicago sativa. These structures were largely composed of meristematic cells but they were not invaded by bacteria. Bacteria were found only within infection threads in root hairs, and within intercellular spaces of the outermost cells of the structures. The donor strain of R. meliloti containing pAK11 or pAK12 in pRme41b initially produced nodules on M. sativa that did not fix nitrogen (Fix-). In these nodules, bacteria were released from infection threads into the host cells but they did not multiply appreciably. Any bacteroids formed degenerated prematurely. In some cases, however, reversion to a Fix+ phenotype occurred after 4 to 6 wk. Bacteria released into newly infected cells in these nodules showed normal development into bacteriods.

Nodulating competitiveness amongst strains of Rhizobium meliloti and R. trifolii

1974 ◽  
Vol 25 (2) ◽  
pp. 317 ◽  
Author(s):  
C Marques Pinto ◽  
PY Yao ◽  
JM Vincent
Keyword(s):  
Medicago Sativa ◽  
Trifolium Repens ◽  
Host Plants ◽  
Rhizobium Meliloti ◽  
Root Surface ◽  
Mixed Infections ◽  
Relative Speed ◽  
Nitrogen Fixing ◽  
Single Culture ◽  
The One

The relative nodulating success of strains of Rhizobium meliloti, with Medicago sativa and M. truncatula, and R. trifolii, with Trifolium repens, T. glomeratum and T. subterraneum, has been determined with inocula of paired competitors, supplied in various proportions. Host plants were raised from surface-sterilized seed, grown on agar in enclosed tubes, and populations and strain ratios were determined on the root surface as well as in the supplied inoculum. The use of heavy inoculum did not prevent all growth, and strain representation on the root surface could differ from that of the inoculum, because of either different adherence or the narrowing of extreme ratios with time. The ratios of strains obtained from nodules when related to those on the root surface yielded a 'competitive index', defined as the ratio of nodules due to each strain under conditions of equal representation on the root. In the five available cases inferior nitrogen-fixing effectiveness of a strain with a particular host was reflected in poor nodulating competitiveness, but similar differences were found in six comparisons between equally effective pairs, and with the one ineffective pair. Competitiveness did not correlate with the relative speed with which the strains produced nodules when used as a single culture or with the number of nodules they produced. Cases of mixed infections were encountered throughout the study; they generally accounted for less than 10% of the nodules typed, but in some combinations of host and strains the figure exceeded 25%.

scholarly journals Quantitative Phosphoproteomic Analysis of Soybean Root Hairs Inoculated with Bradyrhizobium japonicum

2012 ◽  
Vol 11 (11) ◽  
pp. 1140-1155 ◽  
Author(s):  
Tran Hong Nha Nguyen ◽  
Laurent Brechenmacher ◽  
Joshua T. Aldrich ◽  
Therese R. Clauss ◽  
Marina A. Gritsenko ◽  
...  
Keyword(s):  
Root Hair ◽  
Bradyrhizobium Japonicum ◽  
Cell Biology ◽  
Magnetic Beads ◽  
Critical Role ◽  
Root Hairs ◽  
Root Surface ◽  
Infection Process ◽  
Root Surface Area ◽  
Soybean Root

Root hairs are single hair-forming cells on roots that function to increase root surface area, enhancing water and nutrient uptake. In leguminous plants, root hairs also play a critical role as the site of infection by symbiotic nitrogen fixing rhizobia, leading to the formation of a novel organ, the nodule. The initial steps in the rhizobia-root hair infection process are known to involve specific receptor kinases and subsequent kinase cascades. Here, we characterize the phosphoproteome of the root hairs and the corresponding stripped roots (i.e. roots from which root hairs were removed) during rhizobial colonization and infection to gain insight into the molecular mechanism of root hair cell biology. We chose soybean (Glycine max L.), one of the most important crop plants in the legume family, for this study because of its larger root size, which permits isolation of sufficient root hair material for phosphoproteomic analysis. Phosphopeptides derived from root hairs and stripped roots, mock inoculated or inoculated with the soybean-specific rhizobium Bradyrhizobium japonicum, were labeled with the isobaric tag eight-plex iTRAQ, enriched using Ni-NTA magnetic beads and subjected to nanoRPLC-MS/MS1 analysis using HCD and decision tree guided CID/ETD strategy. A total of 1625 unique phosphopeptides, spanning 1659 nonredundant phosphorylation sites, were detected from 1126 soybean phosphoproteins. Among them, 273 phosphopeptides corresponding to 240 phosphoproteins were found to be significantly regulated (>1.5-fold abundance change) in response to inoculation with B. japonicum. The data reveal unique features of the soybean root hair phosphoproteome, including root hair and stripped root-specific phosphorylation suggesting a complex network of kinase-substrate and phosphatase-substrate interactions in response to rhizobial inoculation.

scholarly journals Succinoglycan Is Required for Initiation and Elongation of Infection Threads during Nodulation of Alfalfa byRhizobium meliloti

1998 ◽  
Vol 180 (19) ◽  
pp. 5183-5191 ◽  
Author(s):  
Hai-Ping Cheng ◽  
Graham C. Walker
Keyword(s):  
Molecular Weight ◽  
Fluorescent Protein ◽  
Rhizobium Meliloti ◽  
Root Hairs ◽  
Invasion Process ◽  
Nitrogen Fixing ◽  
Excess Production ◽  
Infection Threads ◽  
Reduced Rate ◽  
Green Fluorescent

ABSTRACT Rhizobium meliloti Rm1021 must be able to synthesize succinoglycan in order to invade successfully the nodules which it elicits on alfalfa and to establish an effective nitrogen-fixing symbiosis. Using R. meliloti cells that express green fluorescent protein (GFP), we have examined the nature of the symbiotic deficiency of exo mutants that are defective or altered in succinoglycan production. Our observations indicate that anexoY mutant, which does not produce succinoglycan, is symbiotically defective because it cannot initiate the formation of infection threads. An exoZ mutant, which produces succinoglycan without the acetyl modification, forms nitrogen-fixing nodules on plants, but it exhibits a reduced efficiency in the initiation and elongation of infection threads. An exoHmutant, which produces symbiotically nonfunctional high-molecular-weight succinoglycan that lacks the succinyl modification, cannot form extended infection threads. Infection threads initiate at a reduced rate and then abort before they reach the base of the root hairs. Overproduction of succinoglycan by theexoS96::Tn5 mutant does not reduce the efficiency of infection thread initiation and elongation, but it does significantly reduce the ability of this mutant to colonize the curled root hairs, which is the first step of the invasion process. TheexoR95::Tn5 mutant, which overproduces succinoglycan to an even greater extent than theexoS96::Tn5 mutant, has completely lost its ability to colonize the curled root hairs. These new observations lead us to propose that succinoglycan is required for both the initiation and elongation of infection threads during nodule invasion and that excess production of succinoglycan interferes with the ability of the rhizobia to colonize curled root hairs.

scholarly journals Root hair phenotypes influence nitrogen acquisition in maize

2021 ◽  
Author(s):  
Patompong Saengwilai ◽  
Christopher Strock ◽  
Harini Rangarajan ◽  
Joseph Chimungu ◽  
Jirawat Salungyu ◽  
...  
Keyword(s):  
Root Hair ◽  
Structural Model ◽  
Root Hairs ◽  
Root Surface ◽  
Root Surface Area ◽  
N Availability ◽  
N Content ◽  
Nitrogen Acquisition ◽  
Field Environment ◽  
N Acquisition

Abstract Background and Aims The utility of root hairs for nitrogen (N) acquisition is poorly understood. Methods We explored the utility of root hairs for N acquisition in the functional-structural model SimRoot and with maize genotypes with variable root hair length (RHL) in greenhouse and field environments. Key Results Simulation results indicate that long, dense root hairs can improve N acquisition under varying N availability. In the greenhouse, ammonium availability had no effect on RHL and low nitrate availability increased RHL, while in the field low N reduced RHL. Longer RHL was associated with 216% increase in biomass and 237% increase in plant N content under low N conditions in the greenhouse and a 250% increase in biomass and 200% increase in plant N content in the field compared with short RHL phenotypes. In a low N field environment, genotypes with long RHL had 267% greater yield than those with short RHL. We speculate that long root hairs improve N capture by increased root surface area and expanded soil exploration beyond the N depletion zone surrounding the root surface. Conclusions We conclude that root hairs play an important role in nitrogen acquisition. We suggest that root hairs merit consideration as a breeding target for improved N acquisition in maize and other crops.

scholarly journals Actin Depolymerizing Factor Modulates Rhizobial Infection and Nodule Organogenesis in Common Bean

2020 ◽  
Vol 21 (6) ◽  
pp. 1970
Author(s):  
Yolanda Ortega-Ortega ◽  
Janet Carrasco-Castilla ◽  
Marco A. Juárez-Verdayes ◽  
Roberto Toscano-Morales ◽  
Citlali Fonseca-García ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Root Hairs ◽  
Fine Tuning ◽  
Actin Binding ◽  
Vascular Bundles ◽  
Nodule Number ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Infection Threads ◽  
Cytoskeletal Rearrangements

Actin plays a critical role in the rhizobium–legume symbiosis. Cytoskeletal rearrangements and changes in actin occur in response to Nod factors secreted by rhizobia during symbiotic interactions with legumes. These cytoskeletal rearrangements are mediated by diverse actin-binding proteins, such as actin depolymerization factors (ADFs). We examined the function of an ADF in the Phaseolus vulgaris–rhizobia symbiotic interaction (PvADFE). PvADFE was preferentially expressed in rhizobia-inoculated roots and nodules. PvADFE promoter activity was associated with root hairs harbouring growing infection threads, cortical cell divisions beneath root hairs, and vascular bundles in mature nodules. Silencing of PvADFE using RNA interference increased the number of infection threads in the transgenic roots, resulting in increased nodule number, nitrogen fixation activity, and average nodule diameter. Conversely, overexpression of PvADFE reduced the nodule number, nitrogen fixation activity, average nodule diameter, as well as NODULE INCEPTION (NIN) and EARLY NODULIN2 (ENOD2) transcript accumulation. Hence, changes in ADFE transcript levels affect rhizobial infection and nodulation, suggesting that ADFE is fine-tuning these processes.

Enhanced root growth of the brb (bald root barley) mutant in drying soil allows similar shoot physiological responses to soil water deficit as wild-type plants

2016 ◽  
Vol 43 (2) ◽  
pp. 199 ◽  
Author(s):  
Ian C. Dodd ◽  
Eugene Diatloff
Keyword(s):  
Water Deficit ◽  
Plant Root ◽  
Physiological Responses ◽  
Root Hairs ◽  
Root Surface ◽  
Root Surface Area ◽  
Genotypic Differences ◽  
Wild Type ◽  
Leaf Elongation ◽  
Hordeum Vulgare L

The genetics, molecular biology and nutrient uptake of plant root hair mutants have been studied in detail, but their physiological responses to soil drying have not. Thus, the root hairless brb (bald root barley) barley (Hordeum vulgare L.) mutant and its wild type (WT) were grown in drying soil. Well-watered, pre-tillering plants showed no genotypic differences in daily transpiration and leaf elongation rate, and the ratio of day to night leaf elongation (D/N, a sensitive indicator of water stress). After withholding water for 25 days, root hydraulic conductivity and xylem ABA concentration were similar between genotypes, but WT plants had more tillers and D/N was more than halved in brb. To avoid possible developmental and nutritional differences confounding responses to water deficit, pre-tillering plants were allowed to dry soils of high and low phosphorus (P) status. Although leaf area, leaf water potential and shoot fresh weight (FW) were similar in the two genotypes, root FW of brb was greater by 44 and 18% in a high and low P soil respectively. This adaptive response allowed brb to maintain similar shoot growth and transpiration as WT plants, despite decreased effective root surface area in the absence of root hairs.

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