Nodule Development Research Articles

The root system of guar: Spatial and temporal analysis of root and nodule development

AbstractGuar (Cyamopsis tetragonoloba [L.] Taub.) is a leguminous crop plant produced in semi‐arid regions worldwide, primarily for industrial uses of guar gum. Little research has been conducted on critical belowground traits of the plant, particularly on spatial and temporal development of the root system, including nodules. Providing such analysis was the objective of this research. We observed root and nodule character traits at regular time intervals in 130‐cm‐tall soil columns sectioned by depth in 2 years. In this tap‐rooted plant, root weight was greatest at the soil surface (0–15 cm) and decreased with depth. Root length density (RLD) from 0 to 15 cm and 15 to 30 cm soil depths was similar. The RLD and root weight were generally minimal in deeper soil layers, although deeper roots seem to play an important role in water uptake for guar, especially in drought conditions. Compared to most crops, guar has fine rooting and a small root‐to‐shoot ratio. At all soil depths analysed, ≥86% of root length was comprised of roots <1 mm in diameter, although most were very fine roots <0.5 mm. The root‐to‐shoot ratio ranged from 0.055 to 0.17 g g−1 over the growing seasons. Significant accumulation of nodule weight occurred by 60 days, as did the first observations of nodule senescence, but nodule growth continued after this time. Most nodules and nodule weight were concentrated near the soil surface and the average weight per nodule decreased with depth, although smaller nodules were present at all depths. Because guar is typically grown in dryland conditions in hot semi‐arid regions, nodules near the soil surface may often be susceptible to shedding or loss of function due to dehydration and/or heat stress and the plant may rely on deeper nodules for N fixation. The basic biological information provided in this report is needed to hasten progress in guar genetic improvement and management.

Title: Hypermethylation of miRNA Genes During Nodule Development.

DNA methylation has recently emerged as a powerful regulatory mechanism controlling the expression of key regulators of various developmental processes, including nodulation. However, the functional role of DNA methylation in regulating the expression of microRNA (miRNA) genes during the formation and development of nitrogen-fixing nodules remains largely unknown. In this study, we profiled DNA methylation patterns of miRNA genes during nodule formation, development, and early senescence stages in soybean (Glycine max) through the analysis of methylC—seq data. Absolute DNA methylation levels in the CG, CHH, and CHH sequence contexts over the promoter and primary transcript regions of miRNA genes were significantly higher in the nodules compared with the corresponding root tissues at these three distinct nodule developmental stages. We identified a total of 82 differentially methylated miRNAs in the nodules compared with roots. Differential DNA methylation of these 82 miRNAs was detected only in the promoter (69), primary transcript region (3), and both in the promoter and primary transcript regions (10). The large majority of these differentially methylated miRNAs were hypermethylated in nodules compared with the corresponding root tissues and were found mainly in the CHH context and showed stage-specific methylation patterns. Differentially methylated regions in the promoters of 25 miRNAs overlapped with transposable elements, a finding that may explain the vulnerability of miRNAs to DNA methylation changes during nodule development. Gene expression analysis of a set of promoter-differentially methylated miRNAs pointed to a negative association between DNA methylation and miRNA expression. Gene Ontology and pathways analyses indicate that changes in DNA methylation of miRNA genes are reprogrammed and contribute to nodule development through indirect regulation of genes involved in cellular processes and pathways with well-established roles in nodulation.

Auxin Response Factor 2 (ARF2), ARF3, and ARF4 Mediate Both Lateral Root and Nitrogen Fixing Nodule Development in Medicago truncatula.

Auxin Response Factors (ARFs) constitute a large family of transcription factors that mediate auxin-regulated developmental programs in plants. ARF2, ARF3, and ARF4 are post-transcriptionally regulated by the microRNA390 (miR390)/trans-acting small interference RNA 3 (TAS3) module through the action of TAS3-derived trans-acting small interfering RNAs (ta-siRNA). We have previously reported that constitutive activation of the miR390/TAS3 pathway promotes elongation of lateral roots but impairs nodule organogenesis and infection by rhizobia during the nitrogen-fixing symbiosis established between Medicago truncatula and its partner Sinorhizobium meliloti. However, the involvement of the targets of the miR390/TAS3 pathway, i.e., MtARF2, MtARF3, MtARF4a, and MtARF4b, in root development and establishment of the nitrogen-fixing symbiosis remained unexplored. Here, promoter:reporter fusions showed that expression of both MtARF3 and MtARF4a was associated with lateral root development; however, only the MtARF4a promoter was active in developing nodules. In addition, up-regulation of MtARF2, MtARF3, and MtARF4a/b in response to rhizobia depends on Nod Factor perception. We provide evidence that simultaneous knockdown of MtARF2, MtARF3, MtARF4a, and MtARF4b or mutation in MtARF4a impaired nodule formation, and reduced initiation and progression of infection events. Silencing of MtARF2, MtARF3, MtARF4a, and MtARF4b altered mRNA levels of the early nodulation gene nodulation signaling pathway 2 (MtNSP2). In addition, roots with reduced levels of MtARF2, MtARF3, MtARF4a, and MtARF4b, as well as arf4a mutant plants exhibited altered root architecture, causing a reduction in primary and lateral root length, but increasing lateral root density. Taken together, our results suggest that these ARF members are common key players of the morphogenetic programs that control root development and the formation of nitrogen-fixing nodules.

Different DNA-binding specificities of NLP and NIN transcription factors underlie nitrate-induced control of root nodulation.

Leguminous plants produce nodules for nitrogen fixation; however, nodule production incurs an energy cost. Therefore, as an adaptive strategy, leguminous plants halt root nodule development when sufficient amounts of nitrogen nutrients, such as nitrate, are present in the environment. Although legume NODULE INCEPTION (NIN)-LIKE PROTEIN (NLP) transcription factors have recently been identified, understanding how nodulation is controlled by nitrate, a fundamental question for nitrate-mediated transcriptional regulation of symbiotic genes, remains elusive. Here, we show that two Lotus japonicus NLPs, NITRATE UNRESPONSIVE SYMBIOSIS 1 (NRSYM1)/LjNLP4 and NRSYM2/LjNLP1, have overlapping functions in the nitrate-induced control of nodulation and act as master regulators for nitrate-dependent gene expression. We further identify candidate target genes of LjNLP4 by combining transcriptome analysis with a DNA affinity purification-seq approach. We then demonstrate that LjNLP4 and LjNIN, a key nodulation-specific regulator and paralog of LjNLP4, have different DNA-binding specificities. Moreover, LjNLP4–LjNIN dimerization underlies LjNLP4-mediated bifunctional transcriptional regulation. These data provide a basic principle for how nitrate controls nodulation through positive and negative regulation of symbiotic genes.

NLP1 reciprocally regulates nitrate inhibition of nodulation through SUNN-CRA2 signaling in Medicago truncatula

Most legume plants can associate with diazotrophic soil bacteria called rhizobia, resulting in new root organs called nodules that enable N2 fixation. Nodulation is an energy-consuming process, and nodule number is tightly regulated by independent systemic signaling pathways controlled by CLE/SUNN and CEP/CRA2. Moreover, nitrate inhibits legume nodulation via local and systemic regulatory pathways. In Medicago truncatula, NLP1 plays important roles in nitrate-induced inhibition of nodulation, but the relationship between systemic and local pathways in mediating nodulation inhibition by nitrate is poorly understood. In this study, we found that nitrate induces CLE35 expression in an NLP1-dependent manner and that NLP1 binds directly to the CLE35 promoter to activate its expression. Grafting experiments revealed that the systemic control of nodule number involves negative regulation by SUNN and positive regulation by CRA2 in the shoot, and that NLP1's control of the inhibition of rhizobial infection, nodule development, and nitrogenase activity in response to nitrate is determined by the root. Unexpectedly, grafting experiments showed that loss of CRA2 in the root increases nodule number at inhibitory nitrate levels, probably because of CEP1/2 upregulation in the cra2 mutants, suggesting that CRA2 exerts active negative feedback regulation in the root.

Sarcoidosis and Tuberculosis: A Case Report and Literature Review

We present a 52-year-old Iraqi female patient who presented with extensive bilateral pulmonary micronodules on a chest X-ray (CXR) after a recent month-long visit to Turkey. She had a history of sarcoidosis, diagnosed 2 years ago, and was initially treated with a tapering dose of prednisone and maintained on a high dose of inhaled budesonide. High resolution computed tomography of the chest showed the new development of pulmonary nodules in a miliary pattern. Infectious causes were excluded with bronchoalveolar lavage. Non-necrotizing granulomatous inflammation and a lymphocyte count of 29% were obtained from a transbronchial lung biopsy and the differential cell count of the bronchoalveolar lavage, respectively. The patient started a treatment regimen of methotrexate and prednisone. Her repeat CXR at a subsequent follow up session showed resolution of the pulmonary micronodules. The association between sarcoidosis and tuberculosis was discussed. Published cases of miliary pulmonary nodules were examined for association with tuberculosis. To date, there has been no definitive evidence of tuberculosis as a cause for sarcoidosis despite the reported association. This case report emphasizes that sarcoidosis patients with pulmonary miliary patterns may have underlying risk factors for tuberculosis, and calls for more investigations to be performed to further delineate the association.

NO Network for Plant-Microbe Communication Underground: A Review.

Mechanisms governing plant–microbe interaction in the rhizosphere attracted a lot of investigative attention in the last decade. The rhizosphere is not simply a source of nutrients and support for the plants; it is rather an ecosystem teeming with diverse flora and fauna including different groups of microbes that are useful as well as harmful for the plants. Plant–microbe interaction occurs via a highly complex communication network that involves sophisticated machinery for the recognition of friend and foe at both sides. On the other hand, nitric oxide (NO) is a key, signaling molecule involved in plant development and defense. Studies on legume–rhizobia symbiosis suggest the involvement of NO during recognition, root hair curling, development of infection threads, nodule development, and nodule senescence. A similar role of NO is also suggested in the case of plant interaction with the mycorrhizal fungi. Another, insight into the plant–microbe interaction in the rhizosphere comes from the recognition of pathogen-associated molecular patterns (PAMPs)/microbe-associated molecular patterns (MAMPs) by the host plant and thereby NO-mediated activation of the defense signaling cascade. Thus, NO plays a major role in mediating the communication between plants and microbes in the rhizosphere. Interestingly, reports suggesting the role of silicon in increasing the number of nodules, enhancing nitrogen fixation, and also the combined effect of silicon and NO may indicate a possibility of their interaction in mediating microbial communication underground. However, the exact role of NO in mediating plant–microbe interaction remains elusive. Therefore, understanding the role of NO in underground plant physiology is very important, especially in relation to the plant’s interaction with the rhizospheric microbiome. This will help devise new strategies for protection against phytopathogens and enhancing plant productivity by promoting symbiotic interaction. This review focuses on the role of NO in plant–microbe communication underground.

Searching for regulators that interact with BELL1 transcription factor and control the legume-rhizobial symbiosis development

The development of nitrogen-fixing nodule, which is formed during legume-rhizobial symbiosis, requires the involvement of cell cycle regulators, phytohormones and homeodomain-containing transcription factors as well as other organogenesis processes. Along with homedomain-containing transcription factors from KNOX family, which participation in the control of nodule development has been studied recently, the role of transcription factors from BELL family in this process remains under-explored. At the same time, transcriptomic data for legumes shows an increase in the expression levels of genes encoding proteins of this family in the plant roots inoculated by Rhizobium. In this work we performed screening of сDNA library, which was generated from inoculated pea roots, using BELL1 protein in yeast two-hybrid system. As a result, we detected two interacting proteins, which are highly interesting for future examination. In the first case we discovered interaction between BELL1 and LysM-containing receptor-like kinase LYK9. Another identified regulator interacting with BELL1 became the glycine-rich protein A3, which may be involved in the regulation of defense reactions in plants and their resistance to phytopathogens. Transcriptomic analysis for pea roots has revealed high expression level of gene, which encodes this protein in the nodules, that may demonstrate its important role in symbiosis regulation.

Mutagenesis of a Lotus japonicus GSK3β/Shaggy-like kinase reveals functionally conserved regulatory residues

The glycogen synthase kinases 3 family (GSK3s/SKs; serine/threonine protein kinases) is conserved throughout eukaryotic evolution from yeast to plants and mammals. We studied a plant SK kinase from Lotus japonicus (LjSK1), previously implicated in nodule development, by enzyme kinetics and mutagenesis studies to compare it to mammalian homologues. Using a phosphorylated peptide as substrate, LjSK1 displays optimum kinase activity at pH 8.0 and 20 °C following Michaelis-Menten kinetics with Km and Vmax values of 48.2 μM and 111.6 nmol/min/mg, respectively, for ATP. Mutation of critical residues, as inferred by sequence comparison to the human homologue GSK3β and molecular modeling, showed a conserved role for Lys167, while residues conferring substrate specificity in the human enzyme are not as significant in modulating LjSK1 substrate specificity. Mutagenesis studies also indicate a regulation mechanism for LjSK1 via proteolysis since removal of a 98 residue long N-terminal segment increases its catalytic efficiency by almost two-fold. In addition, we evaluated the alteration of LjSK1 kinase activity in planta, by overexpressing the mutant variants in hairy-roots and a phenotype in nodulation and lateral root development was verified.

Evaluation of biochar in the root nodulation of Acacia mangium Willd. in a nursery

Organic matter stabilized in the form of biochar has benefits in a nursery for the physico-chemical and biological properties of substrates derived from forest propagation. With biochars from Acacia mangium Willd. (BAM) residue increases for agricultural production in nurseries have been reported. In this research, we evaluated the effect of different levels of this biochar and its mixture with a synthetic fertilizer (SF) on the root nodulation of A. mangium seedlings. Nine treatments were established to assess the effects on volume and nodule count. Two analyses were performed on a volume using the Kruskal-Wallis test and on counting using the Chi-square test of homogeneity distribution. The results of a subsequent comparison between treatments highlighted higher nodule volumes in treatments with BAM and a mixture with SF compared to those of only SF. The distribution of the nodule count was not homogeneous among treatments. The treatment 80 ton·ha−1 of BAM and 50% of SF produced a greater number of nodules compared to the control. All treatments with higher nodule volumes contained BAM to some degree. Biochar seems likely to contribute to increased volume and nodule count, which could suggest greater potential in the population of microorganisms associated with the development of nodules in seedlings.

Functional analysis of heavy metal transporter HMA5 gene in symbiotic nodulation of <italic>Medicago truncatula</italic>

<p indent=0mm>Leguminous plants are able to grow in a nitrogen-deprived environment because they have evolved a symbiotic relationship with rhizobia in the soil, leading to the formation of new organs, namely nodules. In root nodules, rhizobia reduce nitrogen to ammonia through biological nitrogen fixation and provide ammonia to the host legumes in exchange for carbon source and energy they need. In the symbiosis, legumes also provide the metal trace elements to rhizobia, including copper (Cu). As one of the essential elements for plant growth, Cu participates in multiple biological processes. However, excess Cu induces oxidative stress to the detriment of many physiological processes including symbiotic nitrogen fixation. Therefore, the copper content in plants must be maintained within a certain physiological range. The higher plants have evolved complex physiological mechanisms to maintain the copper homeostasis in cells. The heavy metal transporter, P-type ATPase (HMA), is mainly involved in the transport of heavy metals including copper in plants. All members of the HMA family in the dicot model plant <italic>Arabidopsis</italic> have been identified and classified. Preliminary research in the laboratory found that HMA5 gene is related to copper stresses and the symbiotic nodulation of <italic>Medicago</italic>. In this study, the function of HMA5 homologous gene was investigated during symbiotic nodulation in <italic>Medicago truncatula</italic> (Mt), a model leguminous plant. A phylogenetic tree was constructed based on the currently classified HMA family genes in Medicago truncatula and the expression patterns of the genes were analyzed. A homologous gene <italic>MTR</italic>_<italic>8g079250</italic> of HMA5 was selected for further study. Subcellular localization assays showed that<italic> MTR_8g079250 </italic>was localized to the cell membrane and nucleus. The fusion expression analysis of GFP::MTR_8g079250 showed that MTR_8g079250 was mainly expressed in the meristem, infection zone and cortex of the nodules, as well as in the stele and cap of the roots. Knockdown of <italic>MTR_8g079250</italic> by RNA interference (RNAi) technology had no significant effect on the symbiotic nitrogen fixation phenotype. However, overexpression of <italic>MTR_8g079250 </italic>impaired the infection process and nodule development. Compared with the control, the fresh weight and nodule number per plant were dramatically reduced in<italic> MTR_8g079250-</italic>overexpression plants. The numbers of the infection threads and nodule primordia were also significantly decreased. Ultrastructure analyses showed that the nodule cells contained fewer bacteria in the overexpression plants. In particular, the remarkable deformation of bacteroids and enlargement of peribacteroid space occurred in the infected cells, suggesting premature aging of the nodules. qRT-PCR analyses showed that the expression levels of the nodulation marker genes, <italic>NIN</italic>, <italic>DMI1</italic>, <italic>ENOD11</italic> and leghemoglobin gene were down-regulated to different extent. These results indicate that the overexpression of<italic> MTR_8g079250</italic> inhibited the symbiotic nodulation. In summary, this study preliminarily assessed the function of HMA5 in symbiotic nodulation, laying a foundation for the subsequent exploration of the absorption, transport and equilibrium mechanisms of copper ions during root nodule symbiosis.

Mitochondrial N-formyl methionine peptides associate with disease activity as well as contribute to neutrophil activation in patients with rheumatoid arthritis

ObjectivesLiterature suggests that neutrophils of patients with rheumatoid arthritis (RA) are primed to respond to N-formyl methionine group (formylated peptides). Animal models indicate that formylated peptides contribute to joint damage via neutrophil recruitment and inflammation in joints. Non-steroidal anti-inflammatory drugs are also known to inhibit formyl peptide-induced neutrophil activation. The predominant source of formylated peptides in sterile inflammatory conditions like RA is mitochondria, organelles with prokaryotic molecular signatures. However, there is no direct evidence of mitochondrial formyl peptides (mtNFPs) in the circulation of patients with RA and their potential role in neutrophil-mediated inflammation in RA, including their clinical significance. MethodsLevels of mtNFPs (total fMet, MT-ND6) were analyzed using ELISA in plasma and serum obtained from patients in 3 cross-sectional RA cohorts (n = 275), a longitudinal inception cohort (n = 192) followed for a median of 8 years, and age/gender-matched healthy controls (total n = 134). Neutrophil activation assays were done in the absence or presence of formyl peptide receptor 1 (FPR1) inhibitor cyclosporine H. ResultsElevated levels of total fMet were observed in the circulation of patients with RA as compared to healthy controls (p < 0.0001) associating with disease activity and could distinguish patients with the active disease from patients with inactive disease or patients in remission. Baseline levels of total fMet correlated with current and future joint involvement, respectively and predicted the development of rheumatoid nodules (OR = 1.2, p = 0.04). Further, total fMet levels improved the prognostic ability of ACPA in predicting erosive disease (OR of 7.9, p = 0.001). Total fMet levels correlated with markers of inflammation and neutrophil activation. Circulating mtNFPs induced neutrophil activation in vitro through FPR1-dependent mechanisms. ConclusionsCirculating mtNFPs could be novel biomarkers of disease monitoring and prognosis for RA and in investigating neutrophil-mediated inflammation in RA. We propose, FPR1 as a novel therapeutic target for RA.

Phospholipase D- and phosphatidic acid-mediated phospholipid metabolism and signaling modulate symbiotic interaction and nodulation in soybean (Glycine max).

Symbiotic rhizobium-legume interactions, such as root hair curling, rhizobial invasion, infection thread expansion, cell division and proliferation of nitrogen-fixing bacteroids, and nodule formation, involve extensive membrane synthesis, lipid remodeling and cytoskeleton dynamics. However, little is known about these membrane-cytoskeleton interfaces and related genes. Here, we report the roles of a major root phospholipase D (PLD), PLDα1, and its enzymatic product, phosphatidic acid (PA), in rhizobium-root interaction and nodulation. PLDα1 was activated and the PA content transiently increased in roots after rhizobial infection. Levels of PLDα1 transcript and PA, as well as actin and tubulin cytoskeleton-related gene expression, changed markedly during root-rhizobium interactions and nodule development. Pre-treatment of the roots of soybean seedlings with n-butanol suppressed the generation of PLD-derived PA, the expression of early nodulation genes and nodule numbers. Overexpression or knockdown of GmPLDα1 resulted in changes in PA levels, glycerolipid profiles, nodule numbers, actin cytoskeleton dynamics, early nodulation gene expression and hormone levels upon rhizobial infection compared with GUS roots. The transcript levels of cytoskeleton-related genes, such as GmACTIN, GmTUBULIN, actin capping protein 1 (GmCP1) and microtubule-associating protein (GmMAP1), were modified in GmPLDα1-altered hairy roots compared with those of GUS roots. Phosphatidic acid physically bound to GmCP1 and GmMAP1, which could be related to cytoskeletal changes in rhizobium-infected GmPLDα1 mutant roots. These data suggest that PLDα1 and PA play important roles in soybean-rhizobium interaction and nodulation. The possible underlying mechanisms, including PLDα1- and PA-mediated lipid signaling, membrane remodeling, cytoskeleton dynamics and related hormone signaling, are discussed herein.

A Stringent-Response-Defective Bradyrhizobium diazoefficiens Strain Does Not Activate the Type 3 Secretion System, Elicits an Early Plant Defense Response, and Circumvents NH4NO3-Induced Inhibition of Nodulation.

When subjected to nutritional stress, bacteria modify their amino acid metabolism and cell division activities by means of the stringent response, which is controlled by the Rsh protein in alphaproteobacteria. An important group of alphaproteobacteria are the rhizobia, which fix atmospheric N2 in symbiosis with legume plants. Although nutritional stress is common for rhizobia while infecting legume roots, the stringent response has scarcely been studied in this group of soil bacteria. In this report, we obtained a mutant with a kanamycin resistance insertion in the rsh gene of Bradyrhizobium diazoefficiens, the N2-fixing symbiont of soybean. This mutant was defective for type 3 secretion system induction, plant defense suppression at early root infection, and nodulation competition. Furthermore, the mutant produced smaller nodules, although with normal morphology, which led to lower plant biomass production. Soybean (Glycine max) genes GmRIC1 and GmRIC2, involved in autoregulation of nodulation, were upregulated in plants inoculated with the mutant under the N-free condition. In addition, when plants were inoculated in the presence of 10 mM NH4NO3, the mutant produced nodules containing bacteroids, and GmRIC1 and GmRIC2 were downregulated. The rsh mutant released more auxin to the culture supernatant than the wild type, which might in part explain its symbiotic behavior in the presence of combined N. These results indicate that the B. diazoefficiens stringent response integrates into the plant defense suppression and regulation of nodulation circuits in soybean, perhaps mediated by the type 3 secretion system.IMPORTANCE The symbiotic N2 fixation carried out between prokaryotic rhizobia and legume plants performs a substantial contribution to the N cycle in the biosphere. This symbiotic association is initiated when rhizobia infect and penetrate the root hairs, which is followed by the growth and development of root nodules, within which the infective rhizobia are established and protected. Thus, the nodule environment allows the expression and function of the enzyme complex that catalyzes N2 fixation. However, during early infection, the rhizobia find a harsh environment while penetrating the root hairs. To cope with this nuisance, the rhizobia mount a stress response known as the stringent response. In turn, the plant regulates nodulation in response to the presence of alternative sources of combined N in the surrounding medium. Control of these processes is crucial for a successful symbiosis, and here we show how the rhizobial stringent response may modulate plant defense suppression and the networks of regulation of nodulation.

Long Term Follow-Up of Patients with Nontoxic Benign Nodular Goiter Treated with 131Iodine Therapy

Background: With the advancement of diagnostic modalities, there is an increase in the number of individuals detected with thyroid nodules. There are multiple treatment options for the management of nontoxic benign nodular goiter. Radioactive iodine results in effective goiter size reduction which can be administered as out-patient basis and is an appropriate alternative for patients with higher risk for surgery. Our group have shown the effectiveness of 131Iodine therapy for nodular nontoxic goiters. We aim to determine the long-term effectiveness of radioactive iodine therapy among patients with nodular nontoxic goiter. Methods: This is a retrospective cohort study of patients with nontoxic benign nodular goiter, negative for malignancy on biopsy who underwent radioactive therapy with a follow-up of ≥36months using ultrasound studies. Thyroid size, number of nodules and size of nodules pre-treatment and ≥36months post-treatment were compared. Results: 63 patients were included with an average follow-up of 73.14 ± 34.87 months. Mean age during radioactive therapy and last follow-up was 41 ± 14 and 47 ± 14 respectively. Significant thyroid size reduction was noted in 92.06% of patients (right thyroid lobe: 47.54 ± 31.25%, left thyroid lobe 47.44 ± 31.82%) while significant reduction in number and size of nodules were noted in 96.82% and 98.41% of patients respectively. No increase in the number of nodules and no development of new nodules were noted among all patients. Conclusion: Radioactive iodine therapy for nontoxic benign nodular goiter produces a sustained reduction in thyroid size, number and size of nodules even after a long follow-up period. Hence, it is a viable alternative to surgical removal of the thyroid offering a lower risk for complication especially among patients who refuse surgery or has a contraindication to surgical management.

The influence of ethylene, gibberellins and brassinosteroids on energy and nitrogen-fixation metabolites in nodule tissue

Legume nodules are a unique plant organ that contain nitrogen-fixing rhizobial bacteria. For this interaction to be mutually beneficial, plant and bacterial metabolism must be precisely co-ordinated. Plant hormones are known to play essential roles during the establishment of legume-rhizobial symbioses but their role in subsequent nodule metabolism has not been explored in any depth. The plant hormones brassinosteroids, ethylene and gibberellins influence legume infection, nodule number and in some cases nodule function. In this paper, the influence of these hormones on nodule metabolism was examined in a series of well characterised pea mutants with altered hormone biosynthesis or response. A targeted set of metabolites involved in nutrient exchange and nitrogen fixation was examined in nodule tissue of mutant and wild type plants. Gibberellin-deficiency had a major negative impact on the level of several major dicarboxylates supplied to rhizobia by the plant and also led to a significant deficit in the amino acids involved in glutamine-aspartate transamination, consistent with the limited bacteroid development and low fixation rate of gibberellin-deficient na mutant nodules. In contrast, no major effects of brassinosteroid-deficiency or ethylene-insensitivity on the key metabolites in these pathways were found. Therefore, although all three hormones influence infection and nodule number, only gibberellin is important for the establishment of a functional nodule metabolome.

Rhizobium leguminosarum Glutathione Peroxidase Is Essential for Oxidative Stress Resistance and Efficient Nodulation.

Glutathione (GSH) plays a key role in regulating the cellular Redox Homeostasis, and appears to be essential for initiation and development of root nodules. Glutathione peroxidase (Gpx) catalyzes the reduction of H2O2 and organic hydroperoxides by oxidation of GSH to oxidized GSH (GSSG), which in turn is reduced by glutathione reductase (GR). However, it has not been determined whether the Rhizobium leguminosarum Gpx or GR is required during symbiotic interactions with pea. To characterize the role of glutathione-dependent enzymes in the symbiotic process, single and double mutants were made in gpxA (encoding glutathione peroxidase) and gshR (encoding glutathione reductase) genes. All the mutations did not affect the rhizobial growth, but they increased the sensitivity of R. leguminosarum strains to H2O2. Mutant in GpxA had no effect on intracellular GSH levels, but can increase the expression of the catalase genes. The gshR mutant can induce the formation of normal nodules, while the gpxA single and double mutants exhibited a nodulation phenotype coupled to more than 50% reduction in the nitrogen fixation capacity, these defects in nodulation were characterized by the formation of ineffective nodules. In addition, the gpxA and gshR double mutant was severely impaired in rhizosphere colonization and competition. Quantitative proteomics using the TMT labeling method was applied to study the differential expression of proteins in bacteroids isolated from pea root nodules. A total of 27 differentially expressed proteins were identified in these root bacteroids including twenty down-regulated and seven up-regulated proteins. By sorting the down-regulated proteins, eight are transporter proteins, seven are dehydrogenase, deoxygenase, oxidase, and hydrolase. Moreover, three down-regulating proteins are directly involved in nodule process.

Involvement of Arachis hypogaea Jasmonate ZIM domain/TIFY proteins in root nodule symbiosis.

Jasmonate ZIM domain (JAZ) proteins are the key negative regulators of jasmonate signaling, an important integrator of plant-microbe relationships. Versatility of jasmonate signaling outcomes are maintained through the multiplicity of JAZ proteins and their definitive functionalities. How jasmonate signaling influences the legume-Rhizobium symbiotic relationship is still unclear. In Arachis hypogaea (peanut), a legume plant, one JAZ sub-family (JAZ1) gene and one TIFY sequence containing protein family member (TIFY8) gene show enhanced expression in the early stage and late stage of root nodule symbiosis (RNS) respectively. In plants, JAZ sub-family proteins belong to a larger TIFY family. Here, this study denotes the first attempt to reveal in planta interactions of downstream jasmonate signaling regulators through proteomics and mass spectrometry to find out the mode of jasmonate signaling participation in the RNS process of A. hypogaea. From 4-day old Bradyrhizobium-infected peanut roots, the JAZ1-protein complex shows its contribution towards the rhizobial entry, nodule development, autoregulation of nodulation and photo-morphogenesis during the early stage of symbiosis. From 30-day old Bradyrhizobium infected roots, the TIFY8-protein complex reveals repressor functionality of TIFY8, suppression of root jasmonate signaling, modulation of root circadian rhythm and nodule development. Cellular localization and expression level of the interaction partners during the nodulation process further substantiate the in planta interaction pairs. This study provides a comprehensive insight into the jasmonate functionality in RNS through modulation of nodule number and development, during the early stage and root circadian rhythm during the late stage of nodulation, through the protein complexes of JAZ1 and TIFY8 respectively in A. hypogaea.

Soybean Yellow Stripe-like 7 is a symbiosome membrane peptide transporter important for nitrogen fixation.

Legumes form a symbiosis with rhizobia that convert atmospheric nitrogen (N2) to ammonia and provide it to the plant in return for a carbon and nutrient supply. Nodules, developed as part of the symbiosis, harbor rhizobia that are enclosed in a plant-derived symbiosome membrane (SM) to form an organelle-like structure called the symbiosome. In mature nodules exchanges between the symbionts occur across the SM. Here we characterize Yellow Stripe-like 7 (GmYSL7), a Yellow stripe-like family member localized on the SM in soybean (Glycine max) nodules. It is expressed specifically in infected cells with expression peaking soon after nitrogenase becomes active. Unlike most YSL family members, GmYSL7 does not transport metals complexed with phytosiderophores. Rather, it transports oligopeptides of between four and 12 amino acids. Silencing GmYSL7 reduces nitrogenase activity and blocks infected cell development so that symbiosomes contain only a single bacteroid. This indicates the substrate of YSL7 is required for proper nodule development, either by promoting symbiosome development directly or by preventing inhibition of development by the plant. RNAseq of nodules where GmYSL7 was silenced suggests that the plant initiates a defense response against rhizobia with genes encoding proteins involved in amino acid export downregulated and some transcripts associated with metal homeostasis altered. These changes may result from the decrease in nitrogen fixation upon GmYSL7 silencing and suggest that the peptide(s) transported by GmYSL7 monitor the functional state of the bacteroids and regulate nodule metabolism and transport processes accordingly. Further work to identify the physiological substrate for GmYSL7 will allow clarification of this role.

Shoot‐derived miR2111 controls legume root and nodule development

Legumes control their nodule numbers through the autoregulation of nodulation (AON). Rhizobia infection stimulates the production of root-derived CLE peptide hormones that are translocated to the shoot where they regulate a new signal. We used soybean to demonstrate that this shoot-derived signal is miR2111, which is transported via phloem to the root where it targets transcripts of Too Much Love (TML), a negative regulator of nodulation. Shoot perception of rhizobia-induced CLE peptides suppresses miR2111 expression, resulting in TML accumulation in roots and subsequent inhibition of nodule organogenesis. Feeding synthetic mature miR2111 via the petiole increased nodule numbers per plant. Likewise, elevating miR2111 availability by over-expression promoted nodulation, while target mimicry of TML induced the opposite effect on nodule development in wild-type plants and alleviated the supernodulating and stunted root growth phenotypes of AON-defective mutants. Additionally, in non-nodulating wild-type plants, ectopic expression of miR2111 significantly enhanced lateral root emergence with a decrease in lateral root length and average root diameter. In contrast, hairy roots constitutively expressing the target mimic construct exhibited reduced lateral root density. Overall, these findings demonstrate that miR2111 is both the critical shoot-to-root factor that positively regulates root nodule development and also acts to shape root system architecture.