scholarly journals Enhanced Nodulation and Nodule Development by nolR Mutants of Sinorhizobium medicae on Specific Medicago Host Genotypes

2014 ◽  
Vol 27 (4) ◽  
pp. 328-335 ◽  
Author(s):  
Masayuki Sugawara ◽  
Michael J. Sadowsky
Keyword(s):  
Sinorhizobium Meliloti ◽  
Regulatory Protein ◽  
Selective Advantage ◽  
Nodule Development ◽  
Nodule Formation ◽  
Wild Type ◽  
Nod Factor ◽  
Transcriptional Regulatory ◽  
Sinorhizobium Medicae ◽  
Nodule Initiation

The nolR gene encodes a negatively acting, transcriptional regulatory protein of core Nod-factor biosynthetic genes in the sinorhizobia. Although previous reports showed that nolR modulates Nod-factor production and enhances nodulation speed of Sinorhizobium meliloti on alfalfa, there have been no reports for the symbiotic function of this gene in the S. medicae–Medicago truncatula symbiosis. Here, we constructed an nolR mutant of S. medicae WSM419 and evaluated mutant and wild-type strains for their nodulation ability, competitiveness, host specificity, and density-dependent nodulation phenotypes. When the mutant was inoculated at low and medium population densities, it showed enhanced nodule formation during the initial stages of nodulation. Results of quantitative competitive nodulation assays indicated that an nolR mutant had 2.3-fold greater competitiveness for nodulation on M. truncatula ‘A17’ than did the wild-type strain. Moreover, the nodulation phenotype of the nolR mutant differed among Medicago genotypes and showed significantly enhanced nodule development on M. tricycla. Taken together, these results indicated that mutation of nolR in S. medicae positively influenced nodule initiation, competitive nodulation, and nodule development at later nodulation stages. This may allow nolR mutants of S. medicae to have a selective advantage under field conditions.

Effects of a Nod-factor-overproducing strain of Sinorhizobium meliloti on the expression of the ENOD40 gene in Melilotus alba

2002 ◽  
Vol 80 (9) ◽  
pp. 907-915 ◽  
Author(s):  
Walter F Giordano ◽  
Michelle R Lum ◽  
Ann M Hirsch
Keyword(s):  
Lateral Root ◽  
Sinorhizobium Meliloti ◽  
Cortical Cell ◽  
Host Cells ◽  
Nodule Development ◽  
Nodule Formation ◽  
Additional Increase ◽  
Nod Factor ◽  
Melilotus Alba ◽  
Different Strains

We have initiated studies on the molecular biology and genetics of white sweetclover (Melilotus alba Desr.) and its responses to inoculation with the nitrogen-fixing symbiont Sinorhizobium meliloti. Early nodulin genes such as ENOD40 serve as markers for the transition from root to nodule development even before visible stages of nodule formation are evident. Using Northern blot analysis, we found that the ENOD40 gene was expressed within 6 h after inoculation with two different strains of S. meliloti, one of which overproduces symbiotic Nod factors. Inoculation with this strain resulted in an additional increase in ENOD40 gene expression over a typical wild-type S. meliloti strain. Moreover, the increase in mRNA brought about by the Nod-factor-overproducing strain 24 h after inoculation was correlated with lateral root formation by using whole-mount in situ hybridization to localize ENOD40 transcripts in lateral root meristems and by counting lateral root initiation sites. Cortical cell divisions were not detected. We also found that nodulation occurred more rapidly on white sweetclover in response to the Nod-factor-overproducing strain, but ultimately there was no difference in nodulation efficiency in terms of nodule number or the number of roots nodulated by the two strains. Also, the two strains could effectively co-colonize the host when inoculated together, although a few host cells were occupied by both strains.Key words: ENOD40, Nod factor, Melilotus, Sinorhizobium, symbiosis.

scholarly journals A Sinorhizobium meliloti Lipopolysaccharide Mutant Altered in Cell Surface Sulfation

2002 ◽  
Vol 184 (23) ◽  
pp. 6681-6689 ◽  
Author(s):  
David H. Keating ◽  
Michael G. Willits ◽  
Sharon R. Long
Keyword(s):  
Cell Surface ◽  
Sinorhizobium Meliloti ◽  
Glucuronic Acid ◽  
Initial Study ◽  
Nodule Development ◽  
Nod Factor ◽  
Legume Symbiosis ◽  
Surface Polysaccharides

ABSTRACT The Rhizobium-legume symbiosis involves the formation of a novel plant organ, the nodule, in which intracellular bacteria reduce molecular dinitrogen in exchange for plant photosynthates. Nodule development requires a bacterial signal referred to as Nod factor, which in Sinorhizobium meliloti is a β-(1,4)-linked tetramer of N-acetylglucosamine containing N-acyl and O-acetyl modifications at the nonreducing end and a critical 6-O-sulfate at the reducing end. This sulfate modification requires the action of three gene products: nodH, which catalyzes the sulfonyl transfer, and nodPQ, which produce the activated form of sulfate, 3′-phosphoadenosine-5′-phosphosulfate. It was previously reported that S. meliloti cell surface polysaccharides are also covalently modified by sulfate in a reaction dependent on NodPQ. We have further characterized this unique form of bacterial carbohydrate modification. Our studies have determined that one of the nodPQ mutant strains used in the initial study of sulfation of cell surface harbored a second unlinked mutation. We cloned the gene affected by this mutation (referred to as lps-212) and found it to be an allele of lpsL, a gene previously predicted to encode a UDP-glucuronic acid epimerase. We demonstrated that lpsL encoded a UDP-glucuronic acid epimerase activity that was reduced in the lps-212 mutant. The lps-212 mutation resulted in an altered lipopolysaccharide structure that was reduced in sulfate modification in vitro and in vivo. Finally, we determined that the lps-212 mutation resulted in a reduced ability to elicit the formation of plant nodules and by altered infection thread structures that aborted prematurely.

scholarly journals MtBZR1 Plays an Important Role in Nodule Development in Medicago truncatula

2019 ◽  
Vol 20 (12) ◽  
pp. 2941
Author(s):  
Can Cui ◽  
Hongfeng Wang ◽  
Limei Hong ◽  
Yiteng Xu ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Normal Growth ◽  
Dry Mass ◽  
Growth Conditions ◽  
Nodule Development ◽  
Functional Study ◽  
Loss Of Function ◽  
Wild Type

Brassinosteroid (BR) is an essential hormone in plant growth and development. The BR signaling pathway was extensively studied, in which BRASSINAZOLE RESISTANT 1 (BZR1) functions as a key regulator. Here, we carried out a functional study of the homolog of BZR1 in Medicago truncatula R108, whose expression was induced in nodules upon Sinorhizobium meliloti 1021 inoculation. We identified a loss-of-function mutant mtbzr1-1 and generated 35S:MtBZR1 transgenic lines for further analysis at the genetic level. Both the mutant and the overexpression lines of MtBZR1 showed no obvious phenotypic changes under normal growth conditions. After S. meliloti 1021 inoculation, however, the shoot and root dry mass was reduced in mtbzr1-1 compared with the wild type, caused by partially impaired nodule development. The transcriptomic analysis identified 1319 differentially expressed genes in mtbzr1-1 compared with wild type, many of which are involved in nodule development and secondary metabolite biosynthesis. Our results demonstrate the role of MtBZR1 in nodule development in M. truncatula, shedding light on the potential role of BR in legume–rhizobium symbiosis.

Effect of rhizobia and soil nitrate on the establishment and functioning of the soybean symbiosis in the field

1984 ◽  
Vol 35 (2) ◽  
pp. 149 ◽  
Author(s):  
DF Herridge ◽  
RJ Roughley ◽  
J Brockwell
Keyword(s):  
Soil Depth ◽  
Root Nodules ◽  
Xylem Sap ◽  
Progressive Increase ◽  
Rhizobium Japonicum ◽  
Nodule Development ◽  
Initial Increase ◽  
Nodule Formation ◽  
Mineral N ◽  
Nodule Initiation

The symbiosis of the root-nodules of Bragg soybean [Glycine max (L.) Merrill] and the relative dependence of the plants on symbiotic and soil sources of N were evaluated in an experiment conducted on a vertisol which was high in organic- and mineral-N, free of Rhizobium japonicum, and where poor nodulation was characteristic of inoculated, new sowings. Effective inoculant containing R. japonicum strain CB 1809 was sprayed into the seed bed at three rates of application (10-fold intervals). Increasing rates of inoculant led to greater numbers of rhizobia in the rhizosphere and in the soil, and to improved nodulation. Uninoculated plants did not nodulate. High soil NO-3 (30 �g N/g, top 30 cm) did not prevent prompt, abundant colonization of rhizospheres by the bacteria from the inoculant, but nodule initiation was delayed and nodule development was retarded until 42 days after sowing. There was an acceleration in nodule formation and development between 42 and 62 days which coincided with a depletion of NO-3 from the top 60 cm of the soil profile. Nodulated and unnodulated soybeans took up NO-3 at similar times and rates to a soil depth of 90 cm; only unnodulated plants utilized soil NO-3 below 90 cm. Vacuum-extracted stem (xylem) exudate was sampled from plants throughout growth and analysed for nitrogenous solutes. The proportion of ureide-N relative to total-solutes-N in xylem sap was used as an index of symbiotic N2-fixation. The initial increase in concentrations of ureides coincided with the period of accelerated nodule formation and development between 42 and 62 days. Thereafter, there was a progressive increase in ureide concentrations in nodulated plants, and the levels were related to rate of inoculation, extent of nodulation, and to the decline in concentrations of soil NO-3. Ureide concentrations in unnodulated plants remained low throughout. The quantities of NO-3-N and �-NH2- N in xylem sap were not related to nodulation. The differences between treatments in terms of whole-plant N and grain N were less than predicted from the symbiotic parameters. This indicated that soybeans compensated for symbiotic deficiencies by more efficient exploitation of soil N and/or by more efficient redistribution of vegetative N into grain N, and that nodulation and soil NO-3 were interactive and complementary in meeting the N requirements of the crop.

scholarly journals Sinorhizobium meliloti Mutants Deficient in Phosphatidylserine Decarboxylase Accumulate Phosphatidylserine and Are Strongly Affected during Symbiosis with Alfalfa

2008 ◽  
Vol 190 (20) ◽  
pp. 6846-6856 ◽  
Author(s):  
Miguel Angel Vences-Guzmán ◽  
Otto Geiger ◽  
Christian Sohlenkamp
Keyword(s):  
Sinorhizobium Meliloti ◽  
Minimal Medium ◽  
Root Nodule ◽  
Membrane Lipids ◽  
Nodule Formation ◽  
Deficient Mutant ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

ABSTRACT Sinorhizobium meliloti contains phosphatidylglycerol, cardiolipin, phosphatidylcholine, and phosphatidylethanolamine (PE) as major membrane lipids. PE is formed in two steps. In the first step, phosphatidylserine synthase (Pss) condenses serine with CDP-diglyceride to form phosphatidylserine (PS), and in the second step, PS is decarboxylated by phosphatidylserine decarboxylase (Psd) to form PE. In this study we identified the sinorhizobial psd gene coding for Psd. A sinorhizobial mutant deficient in psd is unable to form PE but accumulates the anionic phospholipid PS. Properties of PE-deficient mutants lacking either Pss or Psd were compared with those of the S. meliloti wild type. Whereas both PE-deficient mutants grew in a wild-type-like manner on many complex media, they were unable to grow on minimal medium containing high phosphate concentrations. Surprisingly, the psd-deficient mutant could grow on minimal medium containing low concentrations of inorganic phosphate, while the pss-deficient mutant could not. Addition of choline to the minimal medium rescued growth of the pss-deficient mutant, CS111, to some extent but inhibited growth of the psd-deficient mutant, MAV01. When the two distinct PE-deficient mutants were analyzed for their ability to form a nitrogen-fixing root nodule symbiosis with their alfalfa host plant, they behaved strikingly differently. The Pss-deficient mutant, CS111, initiated nodule formation at about the same time point as the wild type but did form about 30% fewer nodules than the wild type. In contrast, the PS-accumulating mutant, MAV01, initiated nodule formation much later than the wild type and formed 90% fewer nodules than the wild type. The few nodules formed by MAV01 seemed to be almost devoid of bacteria and were unable to fix nitrogen. Leaves of alfalfa plants inoculated with the mutant MAV01 were yellowish, indicating that the plants were starved for nitrogen. Therefore, changes in lipid composition, including the accumulation of bacterial PS, prevent the establishment of a nitrogen-fixing root nodule symbiosis.

scholarly journals Spontaneous Root-Nodule Formation in the Model Legume Lotus japonicus: A Novel Class of Mutants Nodulates in the Absence of Rhizobia

2006 ◽  
Vol 19 (4) ◽  
pp. 373-382 ◽  
Author(s):  
Leïla Tirichine ◽  
Euan K. James ◽  
Niels Sandal ◽  
Jens Stougaard
Keyword(s):  
Root Nodule ◽  
Lotus Japonicus ◽  
Nodule Development ◽  
Nodule Formation ◽  
Wild Type ◽  
Model Legume ◽  
Isolation And Characterization ◽  
Mutant Lines ◽  
Spontaneous Nodules

Root-nodule development in legumes is an inducible developmental process initially triggered by perception of lipochitin-oligosaccharide signals secreted by the bacterial microsymbiont. In nature, rhizobial colonization and invasion of the legume root is therefore a prerequisite for formation of nitrogen-fixing root nodules. Here, we report isolation and characterization of chemically induced spontaneously nodulating mutants in a model legume amenable to molecular genetics. Six mutant lines of Lotus japonicus were identified in a screen for spontaneous nodule development under axenic conditions, i.e., in the absence of rhizobia. Spontaneous nodules do not contain rhizobia, bacteroids, or infection threads. Phenotypically, they resemble ineffective white nodules formed by some bacterial mutants on wild-type plants or certain plant mutants inoculated with wild-type Mesorhizobium loti. Spontaneous nodules formed on mutant lines show the ontogeny and characteristic histological features described for rhizobia-induced nodules on wild-type plants. Physiological responses to nitrate and ethylene are also maintained, as elevated levels inhibit spontaneous nodulation. Activation of the nodule developmental program in spontaneous nodules was shown for the early nodulin genes Enod2 and Nin, which are both upregulated in spontaneous nodules as well as in rhizobial nodules. Both monogenic recessive and dominant spontaneous nodule formation (snf) mutations were isolated in this mutant screen, and map positions were determined for three loci. We suggest that future molecular characterization of these mutants will identify key plant determinants involved in regulating nodulation and provide new insight into plant organ development.

Induction of pseudohyphal growth by overexpression of PHD1, a Saccharomyces cerevisiae gene related to transcriptional regulators of fungal development

1994 ◽  
Vol 14 (3) ◽  
pp. 2100-2112
Author(s):  
C J Gimeno ◽  
G R Fink
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Regulatory Protein ◽  
Binding Motif ◽  
Alpha Cells ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Haploid Strain ◽  
Pseudohyphal Growth ◽  
Acid Protein ◽  
Transcriptional Regulatory

When starved for nitrogen, MATa/MAT alpha cells of the budding yeast Saccharomyces cerevisiae undergo a dimorphic transition to pseudohyphal growth. A visual genetic screen, called PHD (pseudohyphal determinant), for S. cerevisiae pseudohyphal growth mutants was developed. The PHD screen was used to identify seven S. cerevisiae genes that when overexpressed in MATa/MAT alpha cells growing on nitrogen starvation medium cause precocious and unusually vigorous pseudohyphal growth. PHD1, a gene whose overexpression induced invasive pseudohyphal growth on a nutritionally rich medium, was characterized. PHD1 maps to chromosome XI and is predicted to encode a 366-amino-acid protein. PHD1 has a SWI4- and MBP1-like DNA binding motif that is 73% identical over 100 amino acids to a region of Aspergillus nidulans StuA. StuA regulates two pseudohyphal growth-like cell divisions during conidiophore morphogenesis. Epitope-tagged PHD1 was localized to the nucleus by indirect immunofluorescence. These facts suggest that PHD1 may function as a transcriptional regulatory protein. Overexpression of PHD1 in wild-type haploid strains does not induce pseudohyphal growth. Interestingly, PHD1 overexpression enhances pseudohyphal growth in a haploid strain that has the diploid polar budding pattern because of a mutation in the BUD4 gene. In addition, wild-type diploid strains lacking PHD1 undergo pseudohyphal growth when starved for nitrogen. The possible functions of PHD1 in pseudohyphal growth and the uses of the PHD screen to identify morphogenetic regulatory genes from heterologous organisms are discussed.

Newly featured infection events in a supernodulating soybean mutant SS2-2 by Bradyrhizobium japonicum

2006 ◽  
Vol 52 (4) ◽  
pp. 328-335 ◽  
Author(s):  
Puji Lestari ◽  
Kyujung Van ◽  
Moon Young Kim ◽  
Byun-Woo Lee ◽  
Suk-Ha Lee
Keyword(s):  
Glycine Max ◽  
Bradyrhizobium Japonicum ◽  
Cortical Cell ◽  
Root Hairs ◽  
Nodule Development ◽  
Nodule Formation ◽  
Vascular Bundles ◽  
Wild Type ◽  
In The Wild ◽  
Supernodulating Mutant

Supernodulating soybean (Glycine max L. Merr.) mutant SS2-2 and its wild-type counterpart, Sinpaldalkong 2, were examined for the microstructural events associated with nodule formation and development. SS2-2 produced a substantially higher percentage of curled root hairs than the wild type, especially at 14 days after inoculation with Bradyrhizobium japonicum. In addition, there was new evidence that in SS2-2, B. japonicum also entered through fissures created by the emerging adventitious root primordia. Early steps of nodule ontogeny were faster in SS2-2, and continued development of initiated nodules was more frequent and occurred at a higher frequency than in the wild type. These data suggest that the early expression of autoregulation is facilitated by decreasing the speed of cortical cell development, leading to the subsequent termination of less-developed nodules. The nodules of SS2-2 developed into spherical nodules like those formed on the wild type. In both the wild type and supernodulating mutant, vascular bundles bifurcate from root stele and branch off in the nodule cortex to surround the central infected zone. These findings indicate that SS2-2 has complete endosymbiosis and forms completely developed nodule vascular bundles like the wild type, but that the speed of nodule ontogeny differs between the wild type and SS2-2. Thus, SS2-2 has a novel symbiotic phenotype with regard to nodule organogenesis.Key words: Bradyrhizobium japonicum, early nodule development, Glycine max, root hair curling, supernodulation.

scholarly journals Spatiotemporal cytokinin signaling imaging reveals IPT3 function in nodule development in Medicago truncatula

2021 ◽  
Author(s):  
Paolo M. Triozzi ◽  
Thomas B. Irving ◽  
Henry W. Schmidt ◽  
Zachary P. Keyser ◽  
Sanhita Chakraborty ◽  
...  
Keyword(s):  
High Resolution ◽  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Nodule Development ◽  
Nodule Formation ◽  
Symbiotic Association ◽  
Loss Of Function ◽  
Cytokinin Signaling ◽  
Tissue Specific

ABSTRACTMost legumes can establish a symbiotic association with soil rhizobia that triggers the development of root nodules. These nodules host the rhizobia and allow them to fix nitrogen efficiently. The perception of bacterial lipo-chitooligosaccharide (LCO) signal in the epidermis initiates a signaling cascade that allows rhizobial intracellular infection in the root and de-differentiation and activation of cell division that gives rise to the nodule. Nodule organogenesis and rhizobial infection need to be coupled in space and time for successful nodulation. The plant hormone cytokinin (CK) acts as an essential positive regulator of nodule organogenesis, and specific CK receptors are required for nodule formation. Temporal regulation of tissue-specific CK signaling and biosynthesis in response to LCOs or Sinorhizobium meliloti inoculation in Medicago truncatula remains poorly understood. In the present study, using a fluorescence-based CK sensor (TCSn::nls:tGFP), we performed a high-resolution tissue-specific temporal characterization of the CK response’s sequential activation during root infection and nodule development in M. truncatula after inoculation with S. meliloti. Loss-of-function mutants of the CK-biosynthetic gene ISOPENTENYL TRANSFERASE 3 (IPT3) showed impairment of nodulation, suggesting that IPT3 is required for nodule development in M. truncatula. Simultaneous live imaging of pIPT3::tdTOMATO and the CK sensor showed that IPT3 induction in the root stele at the base of nodule primordium contributes to CK biosynthesis, which in turn promotes expression of positive regulators of nodule organogenesis in M. truncatula.One-sentence summaryHigh-resolution spatiotemporal imaging of cytokinin signaling reveals IPT3 function during indeterminate nodule development in Medicago truncatula

scholarly journals Sinorhizobium medicae WSM419 genes that improve symbiosis between Sinorhizobium meliloti Rm1021 and Medicago truncatula Jemalong A17 and in other symbiotic systems

2021 ◽  
Author(s):  
Prithwi Ghosh ◽  
Katie N. Adolphsen ◽  
Svetlana N. Yurgel ◽  
Michael L. Kahn
Keyword(s):  
Plant Growth ◽  
Medicago Truncatula ◽  
Pathogenic Bacteria ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Nodule Formation ◽  
New Genes ◽  
Sinorhizobium Medicae ◽  
Different Strains ◽  
Vigorous Plant

Some soil bacteria called rhizobia can interact symbiotically with legumes in which they form nodules on the plant roots where they can reduce atmospheric dinitrogen to ammonia, a form of nitrogen that can be used by growing plants. Rhizobia/plant combinations can differ in how successful this symbiosis is—Sinorhizobium meliloti Rm1021 forms a relatively ineffective symbiosis with Medicago truncatula Jemalong A17 but Sinorhizobium medicae WSM419 is able to support more vigorous plant growth. Using proteomic data from free-living and symbiotic S. medicae WSM419, we previously identified a subset of proteins that were not closely related to any S. meliloti Rm1021 proteins and speculated that adding one or more of these proteins to S. meliloti Rm1021 would increase its effectiveness on M. truncatula A17. Three genes, Smed_3503, Smed_5985, and Smed_6456, were cloned into S. meliloti Rm1021 downstream of the E. coli lacZ promoter. Strains with these genes increased nodulation and improved plant growth, individually and in combination with one another. Smed_3503, renamed iseA (increased symbiotic effectiveness) had the largest impact, increasing M. truncatula biomass by 61%. iseA homologs were present in all currently sequenced S. medicae strains but were infrequent in other Sinorhizobium isolates. Rhizobium leguminosarum bv. viciae 3841 containing iseA led to more nodules on pea and lentil. Split root experiments with M. truncatula A17 indicated that S. meliloti Rm1021 carrying the S. medicae iseA is less sensitive to plant induced resistance to rhizobial infection, suggesting an interaction with the plant’s regulation of nodule formation. IMPORTANCE The legume symbiosis with rhizobia is highly specific. Rhizobia that can nodulate and fix nitrogen on one legume species are often unable to associate with a different species. The interaction can be more subtle—symbiotically enhanced growth of the host plant can differ substantially when nodules are formed by different rhizobial isolates of a species, much like disease severity can differ when conspecific isolates of pathogenic bacteria infect different cultivars. Much is known about bacterial genes essential for a productive symbiosis, but less is understood about genes that marginally improve performance. We used a proteomic strategy to identify Sinorhizobium genes that contribute to plant growth differences that are seen when two different strains nodulate M. truncatula A17. These genes could also alter the symbiosis between R. leguminosarum bv. viciae 3841 and pea or lentil, suggesting that this approach may identify new genes that may more generally contribute to symbiotic productivity.

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