Nodule Activity Research Articles

Abscopal effect after bronchial artery embolization for cancer-related hemoptysis

AbstractThe abscopal effect, a rare phenomenon in cancer treatment, involves tumor regression in a distant location from the targeted therapy. This case focuses on a 74-year-old woman with metastatic papillary thyroid cancer. Despite prior treatments, she experienced pulmonary nodule progression and hemoptysis. Bland particle embolization was performed on the right bronchial artery branches supplying lung metastases, leading to significant reductions in size, number, and metabolic activity of the right-sided nodules and decreased metabolic activity of the untreated left-sided nodules, without additional cancer-related treatments. The abscopal effect has been observed with various interventional oncologic procedures, indicating a potential role in stimulating the immune response and altering the tumor microenvironment. Further investigation is needed to understand bland embolization's immunomodulatory effects and implications for triggering the abscopal effect.

Zinc mediates control of nitrogen fixation via transcription factor filamentation

Plants adapt to fluctuating environmental conditions by adjusting their metabolism and gene expression to maintain fitness1. In legumes, nitrogen homeostasis is maintained by balancing nitrogen acquired from soil resources with nitrogen fixation by symbiotic bacteria in root nodules2–8. Here we show that zinc, an essential plant micronutrient, acts as an intracellular second messenger that connects environmental changes to transcription factor control of metabolic activity in root nodules. We identify a transcriptional regulator, FIXATION UNDER NITRATE (FUN), which acts as a sensor, with zinc controlling the transition between an inactive filamentous megastructure and an active transcriptional regulator. Lower zinc concentrations in the nodule, which we show occur in response to higher levels of soil nitrate, dissociates the filament and activates FUN. FUN then directly targets multiple pathways to initiate breakdown of the nodule. The zinc-dependent filamentation mechanism thus establishes a concentration readout to adapt nodule function to the environmental nitrogen conditions. In a wider perspective, these results have implications for understanding the roles of metal ions in integration of environmental signals with plant development and optimizing delivery of fixed nitrogen in legume crops.

Nitrogen inhibition of nitrogenase activity involves the modulation of cytosolic invertase in soybean nodule

Legume symbiotic nitrogen fixation (SNF) is suppressed by inorganic N in the soil. High N inhibition of nitrogenase activity is associated with the deprivation of carbon allocation and metabolism in nodules. However, the underlying molecular mechanisms remain unclear. Here, we identify GmCIN1 which encodes a cytosolic invertase, as a gateway for the N-tuning of sucrose utilization in nodules. GmCIN1 is enriched in mature soybean nodules and its expression is regulated by nitrogen status. The knockout of GmCIN1 using genome editing partially mimics the inhibitory effects of N on nitrogenase activity and sugar content and the impact of high N on nodule transcriptomes. This indicates that GmCIN1 partially mediates the high N inhibition of nodule activity. Moreover, ChIP-qPCR and EMSA reveal that SNAP1/2 transcription factors directly bind to the GmCIN1 promoter. In addition, SNAP1/2 may be involved in the repression of GmCIN1 expression in mature nodules at high N concentrations. Our findings provide insights into the involvement of the transcriptional tuning of C metabolism genes by N-signaling modulators in the N-induced inhibition of nitrogenase activity.

Impact of biological fungicides on the formation and functioning of symbiotic system soybean–Bradyrhizobium japonicum

Background. In order to reduce the negative impact of mineral fertilizers and pesticides on agroecosystems, environmentally friendly plant protection systems are increasingly being utilized in soybean cultivation technologies. These systems aim to provide essential nutrients to plants while minimizing ecological harm. Materials and Methods. In vegetative studies, the processes of formation and functioning of symbiotic systems in soybeans with active strains of nodulating bacteria Bradyrhizobium japonicum (РC07, PC09, B78, B144) were investigated under the influence of pre-sowing seed treatment with the biofungicides Mycosan-N and Phytocide-r. Microbiological, physiological, statistical methods, and gas chromatography were employed in the research. Results. The impact of biological fungicides on the nodulation activity of nodule bacteria has been identified. It was determined that with comprehensive treatment of soybean seeds with B. japonicum РC07 and Mycosan-N, the mass of nodules formed on the roots exceeded that of the control plants by 7‒22 %, and under the influence of Phytocide-r, the mass was lower by 6‒20 % throughout the vegetation period. With the combined application of B. japonicum PC09 and Mycosan-N, a decrease in the number of root nodules by 8‒25 % and a reduction in their mass by 18‒35 % was observed throughout the vegetation period. Under the influence of Phytocide-r, with the inoculation of rhizobia strain PC09, the number of nodules was lower compared to the control plants only in the full flowering stage. At the same time, the reduction in their mass was 6‒20 % throughout the entire observation period. A stimulating effect of both biofungicides on the formation of the symbiotic apparatus involving strains B. japonicum B78 and B144 has been identified. With the combined application of B. japonicum РC07 and Phytocide-r, nitrogenase activity of symbiotic systems decreased by 7 % only in the stage of three true leaves compared to plants whose seeds were treated only with rhizobia. The nitrogenase activity of symbiotic systems formed with the participation of B. japonicum B78 and under the influence of Mycosan-N increased by 28 %, 15 %, and 12 % in the stages of three true leaves, budding, and full flowering, respectively. The action of Phytocide-r, with the inoculation by the nodule bacteria B78, resulted in an increase in nitrogenase activity by 14 % only in the budding stage. Under the comprehensive treatment of soybean seeds with involved biofungicides and B. japonicum B144, an increase in the intensity of N2 assimilation was noted by 29‒34 % in the stage of three true leaves and by 10‒16 % in the budding stage. Conclusions. The application of a scientifically justified selection of rhizobial strains and biological plant protection agents for pre-sowing treatment of soybean seeds will enable a more complete realization of their nitrogen-fixing potential and phytoprotective effects.

Increased dependence on nitrogen-fixation of a native legume in competition with an invasive plant

Suppression of roots and/or their symbiotic microorganisms, such as mycorrhizal fungi and rhizobia, is an effective way for alien plants to outcompete native plants. However, little is known about how invasive and native plants interact with the quantity and activity of nutrient-acquisition agents. Here a pot experiment was conducted with monoculture and mixed plantings of an invasive plant, Xanthium strumarium, and a common native legume, Glycine max. We measured traits related to root and nodule quantity and activity and mycorrhizal colonization. Compared to the monoculture, fine root quantity (biomass, surface area) and activity (root nitrogen (N) concentration, acid phosphatase activity) of G. max decreased in mixed plantings; nodule quantity (biomass) decreased by 45%, while nodule activity in N-fixing via rhizobium increased by 106%; mycorrhizal colonization was unaffected. Contribution of N fixation to leaf N content in G. max increased in the mixed plantings, and this increase was attributed to a decrease in the rhizosphere soil N of G. max in the mixed plantings. Increased root quantity and activity, along with a higher mycorrhizal association was observed in X. strumarium in the mixed compared to monoculture. Together, the invasive plant did not directly scavenge N from nodule-fixed N, but rather depleted the rhizosphere soil N of the legume, thereby stimulating the activity of N-fixation and increasing the dependence of the native legume on this N source. The quantity–activity framework holds promise for future studies on how native legumes respond to alien plant invasions.

Steps toward developing legume cover crop varieties: Study of biomass and nitrogen partitioning and within‐plant δ115N variation of faba bean at different growth stages

AbstractModern legumes are engineered to enhance nutrient allocation to grains and maximize harvest index (HI) and yield. Breeding legumes for cover crop requires optimizing source‐sink relationship to prolong nutrient allocation to vegetative organs, support post‐flowering nodule activity, and extend biological nitrogen fixation (BNF). We studied the variation of faba bean (Vicia faba) germplasm for biomass (DM) and nitrogen (N) allocation to plant organs at the lower and upper parts of the canopy. Three genotypes were established during the 2019 and 2020 growing seasons, and DM, N, and δ15N of upper and lower leaves, stems, pods, seeds, and pod shells were quantified at vegetative, first‐pod, and full‐pod stages. Of the three genotypes, PI 678631 displayed early vigor, allocated more DM and N in vegetative organs, and accumulated more total DM and N than Windsor and PI 655333 by first‐pod stage. The advantage of PI 678631 over the other two genotypes seemed to be associated with smaller allocation of DM and N in pods at early reproductive phase. These findings support existing variations within faba bean germplasm that can be used to improve its ecosystem service as cover crop. Within‐plant variation of δ15N was minimal, suggesting that under favorable soil N and moisture where N remobilization is low, vegetative organs can serve as proxies to estimate the entire plant %Ndfa (proportion of plant N derived from the atmosphere) prior to plant maturity. The δ15N of plant organs at vegetative and early‐pod stages were similar and consistent with the only whole plant δ15N measurement in 2020.

Visualization and Quantitative Evaluation of Functional Structures of Soybean Root Nodules via Synchrotron X-ray Imaging.

The efficiency of N2-fixation in legume-rhizobia symbiosis is a function of root nodule activity. Nodules consist of 2 functionally important tissues: (a) a central infected zone (CIZ), colonized by rhizobia bacteria, which serves as the site of N2-fixation, and (b) vascular bundles (VBs), serving as conduits for the transport of water, nutrients, and fixed nitrogen compounds between the nodules and plant. A quantitative evaluation of these tissues is essential to unravel their functional importance in N2-fixation. Employing synchrotron-based x-ray microcomputed tomography (SR-μCT) at submicron resolutions, we obtained high-quality tomograms of fresh soybean root nodules in a non-invasive manner. A semi-automated segmentation algorithm was employed to generate 3-dimensional (3D) models of the internal root nodule structure of the CIZ and VBs, and their volumes were quantified based on the reconstructed 3D structures. Furthermore, synchrotron x-ray fluorescence imaging revealed a distinctive localization of Fe within CIZ tissue and Zn within VBs, allowing for their visualization in 2 dimensions. This study represents a pioneer application of the SR-μCT technique for volumetric quantification of CIZ and VB tissues in fresh, intact soybean root nodules. The proposed methods enable the exploitation of root nodule's anatomical features as novel traits in breeding, aiming to enhance N2-fixation through improved root nodule activity.

THE INFLUENCE OF PENICILLIUM FUNGI ISOLATED FROM SOYBEAN ROOTS ON THE SYMBIOTIC SYSTEM “GLYCINE MAX – BRADYRHIZOBIUM JAPONICUM” AND CROP PRODUCTIVITY

Objective. Identify new strains of Penicillium endophytic fungi by morphological and cultural properties, study their influence on the symbiotic system “Glycine max – Bradyrhizobium japonicum” and soybean productivity. Methods. Microbiological (cultivation of endophytic fungi, preparation of spore suspensions, determination of spore titre in suspensions, light microscopy), gas chromatographic (determination of nitrogenase activity of soybean nodules), vegetation and field small-plot experiments (study of the effect of endophytic fungi on symbiotic and morphometric parameters of soybean plants and crop yield when growing on sod-podzolic soil), statistical. Results. New strains of Penicillium endophytic fungi are attributed to the species P. funiculosum Thom, P. variabile Sopp, P. glauco-lanosum Chalabuda, and P. steckii Zaleski based on their morphological and cultural characteristics. Under the conditions of the vegetation experiment, the positive influence of the studied strains on the symbiotic parameters of soybeans was shown. A tendency towards an increase in the number of nodules versus the control in all variants, an increase in the mass of nodules in the variants when soybean seeds were treated with spores of P. variabile 20173 and P. funiculosum 20312 by 28.4 % and 36.4 %, respectively, an increase in the nitrogenase activity of nodules by 29.8–38.5 % in variants with the use of P. stekii 2204, P. glauco-lanosum 20401, P. variabile 20173 was registered. The results of the study of soybean symbiotic parameters under the conditions of the field experiment generally confirmed the corresponding data of the vegetation experiment. Inoculation of soybean seeds with spores of Penicillium endophytic fungi contributed to an increase of the morphometric parameters of plants, namely: height — by 4.6–6.2 cm in all variants of the experiment, above-ground mass of dried plants — by 11.1–19.0 % when treated with P. stekii 2204, P. glauco-lanosum 20401, P. variabile 20173, mass of dry roots — by 13.2 % and 18.4 % with P. funiculosum 20312 and P. variabile 20173. The results of the field experiment proved the positive influence of new strains of endophytic fungi on soybean yield: when soybean seeds were inoculated with P. variabile 20173, P. funiculosum 20312 and P. stekii 2204, the increase in grain productivity was on average from 11.8 % to 17.3 %. The weight of 1000 grains increased by 3.8–5.1 % in variants using P. variabile 20173, P. glauco-lanosum 20401, P. stekii 2204. Conclusion. Penicillium endophytic fungi, which belong to the species P. funiculosum, P. variabile, P. glauco-lanosum and P. stekii, were isolated from the tissues of soybean roots. It was found that Penicillium endophytic fungi have a positive influence on the functioning of the symbiotic system “Glycine max – Bradyrhizobium japonicum” and soybean yield.

COMPLEX INOCULATION OF SOYBEANS WITH NODULE BACTERIA BRADYRHIZOBIUM JAPONICUM AS A MEASURE TO OPTIMIZE SYMBIOTIC NITROGEN FIXATION

Objective. Establish effective mixed inoculants for soybeans based on new active strains of Bradyrhizobium japonicum with different intensity and dynamics of nitrogen-fixing activity to improve nodulation processes and functional activity of legume-rhizobia symbiosis. Methods. Microbiological, physiological, statistical, gas chromatography. Legume-rhizobia systems based on Glycine max L. (Merill) soybean, variety Samorodok, were studied using recombinant strains of B. japonicum: B199, B201, Д47, Д48, Д52, Д60, Д63. Monoinoculation of soybean with B. japonicum 634б served as the control. Results. Mixed inoculation of B. japonicum ensured positive ontogenetic dynamics of root nodule formation in soybean. The indicator of the number of root nodules in experimental plants was 1.2–1.9 times higher versus the control plants from Day 18 to 45 of soybean vegetation. When soybeans were inoculated with B. japonicum 634б + B201 and 634б + Д 52, the mass of nodules at Day 45 of vegetation increased by 30.0–35.3 % versus the control and was the highest (1.10–1.15 g/plant) among the studied variants, as a result of the strengthening effect of complex bacterization. A positive synergistic effect of the combined use of strains was obtained — intensification of the nitrogen-fixing activity of soybean root nodules. In the phase of budding/beginning of flowering and full flowering under combined inoculation with active strains of B. japonicum 634б + Д47, 634б + Д52 and 634б + В201, nitrogen fixation of soybean nodules increased by 10.7–25.5 % (at Day 32), by 13.2–30.9 % (at Day 38), and was also 2.3–2.8 times higher in the phase of full flowering (Day 45 of soybean vegetation) versus the similar indicator of control plants. In the phase of full flowering of plants (Day 45 of vegetation), under mixed inoculation with strains of B. japonicum 634б + Д47, 634б + В201, 634б + Д52 and В201 + Д52, the aboveground mass of plants exceeded that of control plants by 8.3–17.2 % variant, which was probably provided by improved conditions of their nitrogen nutrition, due to enhanced assimilation of N2 by root nodules. The most developed root system was in soybeans inoculated with strains B. japonicum 634б and B. japonicum 634б + Д52, B. japonicum 634б + В201 and B. japonicum Д48 + Д52. Conclusion. Symbiotic features of active recombinant strains of B. japonicum and their variability in functional activity at different stages of soybean ontogenesis should be taken into account when creating complex nitrogen-fixing bacterial preparations for soybeans with the effect of microbiological synergy.

Localized osmotic stress activates systemic responses to N limitation in Medicago truncatula-Sinorhizobium symbiotic plants.

In mature symbiotic root nodules, differentiated rhizobia fix atmospheric dinitrogen and provide ammonium to fulfill the plant nitrogen (N) demand. The plant enables this process by providing photosynthates to the nodules. The symbiosis is adjusted to the whole plant N demand thanks to systemic N signaling controlling nodule development. Symbiotic plants under N deficit stimulate nodule expansion and activate nodule senescence under N satiety. Besides, nodules are highly sensitive to drought. Here, we used split-root systems to characterize the systemic responses of symbiotic plants to a localized osmotic stress. We showed that polyéthylène glycol (PEG) application rapidly inhibited the symbiotic dinitrogen fixation activity of nodules locally exposed to the treatment, resulting to the N limitation of the plant supplied exclusively by symbiotic dinitrogen fixation. The localized PEG treatment triggered systemic signaling stimulating nodule development in the distant untreated roots. This response was associated with an enhancement of the sucrose allocation. Our analyses showed that transcriptomic reprogramming associated with PEG and N deficit systemic signaling(s) shared many targets transcripts. Altogether, our study suggests that systemic N signaling is a component of the adaptation of the symbiotic plant to the local variations of its edaphic environment.

Viability of Nodule Bacteria Bradyrhizobium japonicummon Soybean Seeds by Treatment With Fungicides During Extended Storage

Background. With the increase in soybean cultivation areas, inoculants are becoming increasingly sought after. They are not only compatible with the original preparations for seed treatment of soybean but also offer the possibility of applying them for several days or even months before sowing into the soil. Objective. The viability of new strains of nodule bacteria Bradyrhizobium japonicum (strain PC07 and strain B78) was investigated on the surface of soybean seeds treated with fungicides Fever and Maxim XL during the extended storage of inoculated seeds. Additionally, their ability for nitrogen fixation under symbiotic conditions was evaluated. Methods. Сultivation, serial dilution method, determination of bacterial titer of inoculants, quantification of colony forming units (CFU), gas chromatography. Results. In laboratory conditions, on the soybean seeds of Almaz and Vasylkivska varieties, the viability of the nodule bacteria B. japonicum PC07 and B78, which are more resistant to the active substances of these fungicides in pure culture, decreased. This reduction was dependent on the storage period, the fungicide used, and the strain of inoculant. One day after inoculation on the seeds without the use of fungicide, 68.6–75.4% CFU of the initial number was retained. Seeds treated with the fungicide Fever contained 36.5–38.3% CFU, and those treated with Maxim XL contained 26.2–27.0% CFU. The use of inoculants based on fungicide-resistant strains of B. japonicum PC07 and B78 also provided high cell viability – 2.41–2.8×106 (on the seeds without treatment), 1.40–1.70×106 (with Fever) and 0.8–1.17×106 (with Maxim XL) CFU/seed after 5 days of storage. The nitrogen-fixing activity of root nodules in soybean plants of Almaz and Vasylkivska varieties, whose seeds were treated with Fever, decreased on both varieties by 18.4–22.4% and 32.1–39.5%, respectively and for treatment with Maxim XL, the reduction was 24.5–33.7% and 47.7–75.2%, respectively, during the storage of seeds for 5 and 7 days before sowing, compared to control variants (seeds without fungicide treatment). Conclusions. The utilization of fungicide-resistant strains of B. japonicum PC07 and B78 for bacterization of soybean seeds treated with fungicides Fever and Maxim XL provides a high inoculation titer during 5 days of storage. Viability of microbial cells on seeds treated with fungicides significantly diminishes during storage for more than 7–14 days. Insufficient titer of CFU of B. japonicum strains PC07 and B78 on the seed surface after 14 days of storage can considerably impede the efficacy of biopreparations. Therefore, it is crucial to seek substances that can enhance the resistance of rhizobia on seeds to the adverse effects of fungicide seed treatment, ensuring a longer period of their viability.

Utilizing Deep Learning and Computed Tomography to Determine Pulmonary Nodule Activity in Patients With Nontuberculous Mycobacterial-Lung Disease.

To develop and evaluate a deep convolutional neural network (DCNN) model for the classification of acute and chronic lung nodules from nontuberculous mycobacterial-lung disease (NTM-LD) on computed tomography (CT). We collected a data set of 650 nodules (316 acute and 334 chronic) from the CT scans of 110 patients with NTM-LD. The data set was divided into training, validation, and test sets in a ratio of 4:1:1. Bounding boxes were used to crop the 2D CT images down to the area of interest. A DCNN model was built using 11 convolutional layers and trained on these images. The performance of the model was evaluated on the hold-out test set and compared with that of 3 radiologists who independently reviewed the images. The DCNN model achieved an area under the receiver operating characteristic curve of 0.806 for differentiating acute and chronic NTM-LD nodules, corresponding to sensitivity, specificity, and accuracy of 76%, 68%, and 72%, respectively. The performance of the model was comparable to that of the 3 radiologists, who had area under the receiver operating characteristic curve, sensitivity, specificity, and accuracy of 0.693 to 0.771, 61% to 82%, 59% to 73%, and 60% to 73%, respectively. This study demonstrated the feasibility of using a DCNN model for the classification of the activity of NTM-LD nodules on chest CT. The model performance was comparable to that of radiologists. This approach can potentially and efficiently improve the diagnosis and management of NTM-LD.

GmNLP7a inhibits soybean nodulation by interacting with GmNIN1a

Nitrogen (N) is an essential macronutrient for plant growth and productivity. Leguminous plants establish symbiotic relationships with nitrogen-fixing rhizobial bacteria to use atmospheric dinitrogen gas to meet high N demand under low-N conditions. Nodule formation and N fixation are energy-consuming processes and are inhibited by nitrate present in the environment. Previous studies in model leguminous plants characterized NIN-LIKE PROTEIN (NLP) proteins that mediate nitrate control of root nodule symbiosis, but the mechanism by which nitrate regulates soybean root nodules via NLP remains unclear. In the soybean genome we found four homologs of AtNLP7, named GmNLP7a–GmNLP7d. We showed that the expression of GmNLP7s is responsive to nitrate but not to rhizobial infection and localized GmNLP7a to the nucleus. Downregulation of GmNLP7s increased nodule number, and overexpression of GmNLP7a (GmNLP7aOE) reduced nodule number regardless of nitrate availability, suggesting a negative role for GmNLP7s in nodulation. Nitrogenase activity in the GmNLP7aOE line was comparable to that of the wild type, indicating that GmNLP7a does not affect mature nodule activity. Overexpression of GmNLP7a downregulated the expression of GmNIN1a and GmENOD40-1. GmNLP7a interacted with GmNIN1a via the PB1 domain. Our results reveal a new regulator of GmNLP7 in nodulation and a molecular mechanism by which nitrate affects nodule number in soybean.

Systemic regulation of nodule structure and assimilated carbon distribution by nitrate in soybean.

The nitrate regulates soybean nodulation and nitrogen fixation systemically, mainly in inhibiting nodule growth and reducing nodule nitrogenase activity, but the reason for its inhibition is still inconclusive. The systemic effect of nitrate on nodule structure, function, and carbon distribution in soybean (Glycine max (L.) Merr.) was studied in a dual-root growth system, with both sides inoculated with rhizobia and only one side subjected to nitrate treatment for four days. The non-nodulating side was genetically devoid of the ability to form nodules. Nutrient solutions with nitrogen concentrations of 0, 100, and 200 mg L-1 were applied as KNO3 to the non-nodulating side, while the nodulating side received a nitrogen-free nutrient solution. Carbon partitioning in roots and nodules was monitored using 13C-labelled CO2. Other nodule responses were measured via the estimation of the nitrogenase activity and the microscopic observation of nodule ultrastructure. Elevated concentrations of nitrate applied on the non-nodulating side caused a decrease in the number of bacteroids, fusion of symbiosomes, enlargement of the peribacteroid spaces, and onset of degradation of poly-β-hydroxybutyrate granules, which is a form of carbon storage in bacteroids. These microscopic observations were associated with a strong decrease in the nitrogenase activity of nodules. Furthermore, our data demonstrate that the assimilated carbon is more likely to be allocated to the non-nodulating roots, as follows from the competition for carbon between the symbiotic and non-symbiotic sides of the dual-root system. We propose that there is no carbon competition between roots and nodules when they are indirectly supplied with nitrate, and that the reduction of carbon fluxes to nodules and roots on the nodulating side is the mechanism by which the plant systemically suppresses nodulation under nitrogen-replete conditions.

Anthracnose Disease and Physiological Aspects of Soybean in Saturated Soil Culture in Tidal Land

Saturated soil culture in tidal land could be an alternative measure for achieving sufficient soybean production to meet demand and reduce the current 56% dependence on imports. Therefore, this study aims to investigate disease development and the nitrogen fixation rate of soybean in water-saturated cultivation on tidal land. It was conducted in Simpang Village, Berbak District, East Tanjung Jabung, Jambi Province, Indonesia, and subjected to a randomized block design as an environmental design. The treatment consisted of 3 water inundation levels in the trench, namely, 15, 20, and 25 cm from the soil surface. The results showed that the height of standing water in a water-saturated cultivation system affected the soil moisture. Furthermore, high soil moisture results in a high anthracnose disease in soybean caused by the fungus Colletotrichumdematinum var. truncatum. The disease attack rate reached 15.7% with 72% soil moisture at a depth of 15 cm below the soil surface. There was also an attack rate of 16.3%, with soil moisture of 70.5% at a depth of 20 cm from the soil surface. The highest percentage of fallen pods in the treatment plots was up to 15cm and 20 cm in standing water, which was 17.3% and 16.7%, respectively. The root nodules' weight decreased in height by 25 cm from the soil surface. Furthermore, the rate of nitrogen fixation decreased, as indicated by a reduction in the activity of the root nodules' acetylene, which decreased at the height of the waterlogging 25 cm from the soil surface. Soybean crop yield was affected by the height of standing water in the trench. The numbers of filled pods, the weight of dry seeds per plant, and the weight of 100 seeds were lower at the height of water 25 cm from the soil surface. Additionally, disease severity was strongly correlated with root nodules and seed/plant dry weight. Increased disease severity significantly contributed to the decline in dry weight of root nodules, very strongly to dry seed/plant weight and moderately to acetylene-reducing activity.

Bacteroid Development, Transcriptome, and Symbiotic Nitrogen-Fixing Comparison of Bradyrhizobium arachidis in Nodules of Peanut (Arachis hypogaea) and Medicinal Legume Sophora flavescens.

Bradyrhizobium arachidis strain CCBAU 051107 could differentiate into swollen and nonswollen bacteroids in determinate root nodules of peanut (Arachis hypogaea) and indeterminate nodules of Sophora flavescens, respectively, with different N2 fixation efficiencies. To reveal the mechanism of bacteroid differentiation and symbiosis efficiency in association with different hosts, morphologies, transcriptomes, and nitrogen fixation efficiencies of the root nodules induced by strain CCBAU 051107 on these two plants were compared. Our results indicated that the nitrogenase activity of peanut nodules was 3 times higher than that of S. flavescens nodules, demonstrating the effects of rhizobium-host interaction on symbiotic effectiveness. With transcriptome comparisons, genes involved in biological nitrogen fixation (BNF) and energy metabolism were upregulated, while those involved in DNA replication, bacterial chemotaxis, and flagellar assembly were significantly downregulated in both types of bacteroids compared with those in free-living cells. However, expression levels of genes involved in BNF, the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway, hydrogenase synthesis, poly-β-hydroxybutyrate (PHB) degradation, and peptidoglycan biosynthesis were significantly greater in the swollen bacteroids of peanut than those in the nonswollen bacteroids of S. flavescens, while contrasting situations were found in expression of genes involved in urea degradation, PHB synthesis, and nitrogen assimilation. Especially higher expression of ureABEF and aspB genes in bacteroids of S. flavescens might imply that the BNF product and nitrogen transport pathway were different from those in peanut. Our study revealed the first differences in bacteroid differentiation and metabolism of these two hosts and will be helpful for us to explore higher-efficiency symbiosis between rhizobia and legumes. IMPORTANCE Rhizobial differentiation into bacteroids in leguminous nodules attracts scientists to investigate its different aspects. The development of bacteroids in the nodule of the important oil crop peanut was first investigated and compared to the status in the nodule of the extremely promiscuous medicinal legume Sophora flavescens by using just a single rhizobial strain of Bradyrhizobium arachidis, CCBAU 051107. This strain differentiates into swollen bacteroids in peanut nodules and nonswollen bacteroids in S. flavescens nodules. The N2-fixing efficiency of the peanut nodules is three times higher than that of S. flavescens. By comparing the transcriptomes of their bacteroids, we found that they have similar gene expression spectra, such as nitrogen fixation and motivity, but different spectra in terms of urease activity and peptidoglycan biosynthesis. Those altered levels of gene expression might be related to their functions and differentiation in respective nodules. Our studies provided novel insight into the rhizobial differentiation and metabolic alteration in different hosts.

Nitrogen and light regulate symbiotic nitrogen fixation by a temperate forest tree.

Symbiotic nitrogen fixation (SNF) is a critical mechanism of ecosystem recovery, and in forests of the eastern United States, the most common tree species that supports SNF is black locust (Robinia pseudoacacia L.). Despite its prevalence, black locust's fixation strategy-whether it maintains fixation at a constant rate (obligate fixation) or reduces its fixation rate (facultative fixation)-is unknown. Here, we examined how nitrogen and light control SNF by black locust, by growing seedlings under two nitrogen levels and across four levels of light. Seedlings were harvested after 12weeks to determine biomass changes, nodule activity, and photosynthetic rates. Black locust seedlings increased biomass growth with increasing light, but only in the absence of nitrogen addition, while seedling root:shoot (biomass) modestly declined with increasing light regardless of nitrogen level. We found that black locust behaved like a facultative fixer, and regulated fixation by excising or maintaining nodules, and by controlling nodule biomass and activity. Specifically, nitrogen addition reduced seedling investment in nodule biomass (g g-1) by 63%, and reduced seedling allocation to nitrogen fixation (µmol C2H4 g-1h-1) by 66%. In contrast, light affected nitrogen fixation through two indirect pathways. First, light increased plant growth, and hence nitrogen demands, which caused an increase in nitrogen fixation proportional to biomass. Second, light increasd photosynthetic activity, which was positively associated with nodule activity, but only in the absence of nitrogen addition. Our findings for how black locust regulates SNF can improve predictions of ecosystem SNF under the changing environmental conditions.

GmYSL7 controls iron uptake, allocation, and cellular response of nodules in soybean.

Iron (Fe) is essential for DNA synthesis, photosynthesis and respiration of plants. The demand for Fe substantially increases during legumes-rhizobia symbiotic nitrogen fixation because of the synthesis of leghemoglobin in the host and Fe-containing proteins in bacteroids. However, the mechanism by which plant controls iron transport to nodules remains largely unknown. Here we demonstrate that GmYSL7 serves as a key regulator controlling Fe uptake from root to nodule and distribution in soybean nodules. GmYSL7 is Fe responsive and GmYSL7 transports iron across the membrane and into the infected cells of nodules. Alterations of GmYSL7 substantially affect iron distribution between root and nodule, resulting in defective growth of nodules and reduced nitrogenase activity. GmYSL7 knockout increases the expression of GmbHLH300, a transcription factor required for Fe response of nodules. Overexpression of GmbHLH300 decreases nodule number, nitrogenase activity and Fe content in nodules. Remarkably, GmbHLH300 directly binds to the promoters of ENOD93 and GmLbs, which regulate nodule number and nitrogenase activity, and represses their transcription. Our data reveal a new role of GmYSL7 in controlling Fe transport from host root to nodule and Fe distribution in nodule cells, and uncover a molecular mechanism by which Fe affects nodule number and nitrogenase activity.

REACTION OF FREE-LIVING AND SYMBIOTIC BRADYRHIZOBIUM JAPONICUM ON THE USE OF SUCCINIC ACID

Objective. Find out the influence of different concentrations of succinic acid on the intensity of growth of Bradyrhizobium japonicim and the activity of symbiotic systems created with their participation. Methods. Microbiological, physiological, statistical, gas chromatography. Results. It was found that the T21-2 strain had a more pronounced reaction to the use of succinic acid than the PC08 strain, regardless of its concentration. Addition of succinic acid to the culture medium of rhizobia at a concentration of 0.01 and 0.02 g/L led to an increase in the titre of bacterial cells of T21- 2 and PC08 strains, while at a concentration of 0.2 g/L it had a toxic effect on the studied strains. Succinic acid at a concentration of 0.01 g/L, both during seed treatment and as a component of the inoculation suspension, significantly activated the processes of formation and functioning of soybean symbiotic systems formed by the T21-2 rhizobia strain. At a concentration of 0.02 g/L, it provided the highest rate of growth of bacterial cells among the studied variants and led to an increase in their titre relative to rhizobia without adding acid, both on day three and four of cultivation. At the same time, regardless of the method of application, this concentration of succinic acid partially inhibited the nodulation activity of T21-2 strain and the nitrogen-fixing activity of the symbiotic systems formed with their participation. Conclusion. Based on the revealed effect of succinic acid on the growth of Bradyrhizobium japonicum in pure culture and on the formation and functioning of symbiosis, we recommend adding succinic acid at a concentration of 0.01 g/L, both as a component of the inoculation suspension, and for pre-sowing seed treatment to increase the activity of soybean-rhizobia symbiotic systems.

The Effect of In Vitro Coinoculation on the Physiological Parameters of White Lupine Plants (Lupinus albus L.)

The aim of the study was to select microbiological inoculants for a specific plant species, i.e., white lupine (Lupinus albus L.), to increase the efficiency of the diazotroph process. The research involved an in vitro assessment of interactions between the symbiotic bacteria (Bradyrhizobium sp. isolated from Nitragina and Nitroflora commercial preparations dedicated to white lupine) and selected endophytes (Pseudomonas fluorescens or Bacillus subtilis) used for seed coinoculation. In addition, selected morphological traits of plants (the weight and length of aboveground and belowground parts) were examined after the inoculation/coinoculation. The degree of root colonisation by selected endophytes used as individual inoculants and in combination with bacteria of the Bradyrhizobium genus was determined. The diazotrophic parameters were also investigated (nitrogenase activity, the number, and weight of nodules). The results showed no antagonistic interactions have been demonstrated between bacterial strains of the genus Bradyrhizobium sp. isolated from Nitragina and Nitroflora, and the endophytes Pseudomonas fluorescens or Bacillus subtilis used for the study. The applied coinoculation in vitro had a stimulating effect on the weight of the stems and roots of white lupine causing an average increase of 13% and 28%, respectively. The level of nitrogenase activity in the coinoculation variants increased from 3.5 nMC2H4 plant−1 h−1 to an average of 32.34 nMC2H4 plant−1 h−1.