Root Nodules Of Plants Research Articles

Alkalinity of Lanzarote soils is a factor shaping rhizobial populations with Sinorhizobium meliloti being the predominant microsymbiont of Lotus lancerottensis

Lotus lancerottensis is an endemic species that grows widely throughout Lanzarote Island (Canary Is.). Characterization of 48 strains isolated from root nodules of plants growing in soils from eleven locations on the island showed that 38 isolates (79.1%) belonged to the species Sinorhizobium meliloti, whereas only six belonged to Mesorhizobium sp., the more common microsymbionts for the Lotus. Other genotypes containing only one isolate were classified as Pararhizobium sp., Sinorhizobium sp., Phyllobacterium sp. and Bradyrhizobium-like. Strains of S. meliloti were distributed along the island and, in most of the localities they were exclusive or major microsymbionts of L. lancerottensis. Phylogeny of the nodulation nodC gene placed the S. meliloti strains within symbiovar lancerottense and the mesorhizobial strains with the symbiovar loti. Although strains from both symbiovars produced effective N2-fixing nodules, S. meliloti symbiovar lancerottense was clearly the predominant microsymbiont of L. lancerottensis. This fact correlated with the better adaptation of strains of this species to the alkaline soils of Lanzarote, as in vitro characterization showed that while the mesorhizobial strains were inhibited by alkaline pH, S. meliloti strains grew well at pH 9.

Microvirga ossetica sp. nov., a species of rhizobia isolated from root nodules of the legume species Vicia alpestris Steven.

Gram-stain-negative strains V5/3MT, V5/5K, V5/5M and V5/13 were isolated from root nodules of Vicia alpestris plants growing in the North Ossetia region (Caucasus). Sequencing of the partial 16S rRNA gene (rrs) and four housekeeping genes (dnaK, gyrB, recA and rpoB) showed that the isolates from V. alpestris were most closely related to the species Microvirga zambiensis (order Rhizobiales, family Methylobacteriaceae) which was described for the single isolate from root nodule of Listia angolensis growing in Zambia. Sequence similarities between the Microvirga-related isolates and M. zambiensis WSM3693T ranged from 98.5 to 98.7 % for rrs and from 79.7 to 95.8 % for housekeeping genes. Cellular fatty acids of the isolates V5/3MT, V5/5K, V5/5M and V5/13 included important amounts of C18 : 1ω7c (54.0-67.2 %), C16 : 0 (6.0-7.8 %), C19 : 0 cyclo ω8c (3.1-10.2 %), summed feature 2 (comprising one or more of iso-C16 : 1 I, C14 : 0 3-OH and unknown ECL 10.938, 5.8-22.5 %) and summed feature 3 (comprising C16 : 1ω7c and/or iso-C15 : 02-OH, 2.9-4.0 %). DNA-DNA hybridization between the isolate V5/3MT and M. zambiensis WSM3693T revealed DNA-DNA relatedness of 35.3 %. Analysis of morphological and physiological features of the novel isolates demonstrated their unique phenotypic profile in comparison with reference strains from closely related species of the genus Microvirga. On the basis of genotypic and phenotypic analysis, a novel species named Microvirga ossetica sp. nov. is proposed. The type strain is V5/3MT (=LMG 29787T=RCAM 02728T). Three additional strains of the species are V5/5K, V5/5M and V5/13.

Host species and environmental variation can influence rhizobial community composition

Summary Nitrogen‐fixing rhizobial mutualists display high levels of genetic and phenotypic diversity at multiple spatial scales. Identifying the ecological and environmental drivers of variation in the genetic composition and function of rhizobial communities is critical to understanding rhizobial impacts on community and ecosystem productivity. In this study, we examined how environmental factors and host species jointly affect rhizobial phenotypic diversity and community structure. Individual host plants of two native Australian legumes, Acacia salicina and A. stenophylla, were inoculated with a community of six rhizobial strains (belonging to three genera) previously characterized for symbiotic effectiveness. The plants were grown in a fully factorial experiment under high and low phosphorus and water, and high or no nitrogen. Half the plants were harvested after 19 weeks and the other half after 30 weeks. The relative abundance of the six rhizobial strains was characterized using amplicon sequencing of the rhizobial 16S rRNA gene from DNA extracted from the root nodules of plants after each harvest. Variation in the relative abundance of the six rhizobial strains was best explained by host species, although interactions between environment and host species also emerged as significant predictors of variation in rhizobial community composition. We detected strong host‐specific interactions for two strains, while two other strains were clearly generalists, being relatively abundant in both host species. For both host species, the two generalist strains were as abundant as the best specialist strain within the rhizobial community. Synthesis. Our study show host species identity as the key determinant of rhizobial community structure within the root nodules of Acacia plants. Strains that were efficient at promoting the growth of their host plant had high relative abundance in experimental communities. Furthermore, interaction among host species, rhizobial host‐range, and environmental variation determine the structure of rhizobial communities, although not in clearly predictable ways. Such interactions contributed to the maintenance (albeit at relatively low frequencies) of ineffective strains in nodule communities. These interacting effects could help to explain why rhizobial communities are functionally diverse, such that specialists, generalists and seemingly ineffective rhizobia, can be simultaneously maintained in rhizosphere communities.

Proposal of a type strain for Frankia alni (Woronin 1866) Von Tubeuf 1895, emended description of Frankia alni, and recognition of Frankia casuarinae sp. nov. and Frankia elaeagni sp. nov.

Before the establishment of pure cultures, the species Frankia alni, 'Frankia casuarinae' and 'Frankia elaeagni' were proposed to encompass all causal agents of the nitrogen-fixing root nodules of dicotyledonous plants from the genera Alnus, Casuarina or Elaeagnus. The sole Frankia species with a validly published name, the type species F. alni, was described by Woronin (1866) as present in the root of alder. Until now no type strain has been designated for F. alni, even though the absence of a type strain has seriously inhibited the application of modern taxonomic methods to the genus Frankia. Thus, we propose that strain ACN14aT, isolated in pure culture from Alnus viridis ssp. crispa with morphological properties matching the original description of F. alni, be recognized as the type strain of this species according to Rule 18f of the International Code of Nomenclature of Bacteria. We compared ACN14aT to two strains, CcI3T and BMG5.12T, isolated from Casuarina cunninghamiana and Elaeagnus angustifolia, respectively, based on chemotaxonomy, phenotype microarray data and molecular data retrieved from genome sequences. All three tested strains grew as branched hyphae, produced vesicles and multilocular sporangia containing non-motile spores and metabolized short fatty acids, TCA-cycle intermediates and carbohydrates. Chemotaxonomically, the three strains were indistinguishable with respect to phospholipids (phosphatidylinositol, diphosphatidylglycerol, glycophospholipids and phosphatidylglycerol) and cell-sugar composition (glucose, mannose, ribose, rhamnose, galactose and xylose, with the latter two being diagnostic for the genus). The major fatty acids identified in all three strains were iso-C16 : 0, C17 : 1ω8c, C15 : 0, C17 : 0 and C16 : 0. ACN14aT and BMG5.12T also shared C15 : 1ω6c, while C18 : 1ω9c was found to be unique to BMG5.12T. The major menaquinones identified in all three novel type strains were MK-9(H8), MK-9(H6) and MK-9(H4). MK-9(H2) was shared by ACN14aT and BMG5.12T, while MK-10(H4) and MK-8(H4) were only found in BMG5.12T. Analysis of 16S rRNA gene sequences showed 98.1-98.9 % identity between strains ACN14aT, CcI3T and BMG5.12T. Digital DNA-DNA hybridization values between the three type strains were well below 70 %. These results confirm the separation of the strains into three distinct species, Frankia alni, Frankia casuarinae sp. nov. and Frankia elaeagni sp. nov. Thus, we propose ACN14aT (=DSM 45986T=CECT 9034T), CcI3T (=DSM 45818T=CECT 9043T) and BMG5.12T (=DSM 46783T=CECT 9031T) as the respective type strains.

INDUCTION OF RESISTANCE AGAINST DAMPING-OFF AND ROOT ROT DISEASES IN FABA BEAN

Faba bean (Vicia faba L.) seeds cv. Misr 1 were treated with Bion (5 mM), salicylic acid (5 mM) as chemical inducers as well as Paenibacillus polymyxa and Trichoderma harzianum as biotic inducers to study their effect on the infection with Rhizoctonia solani and Fusarium solani f. sp. fabae under greenhouse and field conditions. Under greenhouse conditions (Agricultural Research Centre, Giza) all treatments induced reduction in the percentages of pre- and post-emergence damping off caused by R. solani or F. solani f. sp. fabae compared to untreated control. The highest percentage of survived plants was achieved from the inducer Bion (92 % and 88%) compared with untreated control (40% and 36%) in the presence of R. solani or F. solani f. sp. fabae respectively. Meantime, there was no significant difference between the Bion and the fungicide Rizolex –T (3 g/Kg seeds) treatments. However, all treatments caused significant increase in the figures of plant height, shoot and root dry weight, nodules number/plant and nodules dry weight over the control treatment grown in infested soil by R. solani or by F. solani f. sp. fabae. The highest values of all growth parameters under study were recorded on faba bean plants check (healthy plants) grown in disinfested soil followed by Bion and Rizolex –T treatments in the presence of R. solani or F. solani f. sp. fabae. There was no significant difference between Bion and Rizolex-T treatments with exception of nodules number and nodules dry weight /plant in the presence of R. solani. On the contrary, there was significant difference between Bion and Rizolex-T treatments with exception of plant height in the presence of F. solani f. sp. fabae. Under field conditions at Giza (Giza Governorate) and Etay El-Baroud (El- Behira Governorate) Agricultural Research Stations during winter season 2013-2014, all the treatments significantly decreased the percentage of pre- and post-emergence damping-off and increased the percentage of survived plants compared with untreated control in two locations with exception of post-emergence percentage figures at Giza Agricultural Research Station. Regarding survived plants, there were no significant differences between the Bion (89.5% and 86.5%) as well as Rizolex-T (90.9% and 88.8%) treatments compared with untreated control (68.3% and 64.3%) at Giza and Etay El-Baroud Agricultural Research Stations respectively. However, all inducer treatments significantly improved growth parameters (i.e. plant height, number of pods/plant, seed weight /plant and one hundred seed weight) as well as yield compared to the untreated control in the two locations. Higher increase in seed yield (ton /feddan) was obtained with Rizolex-T and Bion treatments (62.2% and 57.9%) respectively, followed by salicylic acid and P. polymyxa with (39.4% and 28.4 %) respectively, increasing over the untreated control calculated as means of the two locations. Activities of peroxidase (PO), polyphenol oxidase (PPO) enzymes and phenol content were determined in faba bean plants treated with different inducers. Bion treatment showed the highest increase in PO and PPO activity, total and free phenols followed by salicylic acid treatment in the presence of R. solani or F. solani f. sp. fabae.

Rhizobium anhuiense as the predominant microsymbionts of Lathyrus maritimus along the Shandong Peninsula seashore line

Beach pea [Lathyrus maritimus Bigelow, or Lathyrus japonicus subsp. maritimus (L.) P.W. Ball] is a wild legume distributed on the seashore line, and the rhizobia nodulating with this plant have been reported only rarely. In order to reveal the diversity of beach pea rhizobia on the seashore line of Shandong Peninsula, China, a total of 124 bacterial strains were isolated from the root nodules of beach pea plants collected from five sites. All the isolates were divided into five recA types after screening by recA gene sequence analysis and they consisted of Rhizobium anhuiense covering 122 symbiotic isolates in three recA types, as well as two single isolates Rhizobium sp. and Rhizobium lusitanum representing distinct recA types. The recA genotype III of R. anhuiense (103 isolates) represented by strain YIC11270 was dominant at all five sampling sites. Identical symbiotic genes (nodC and nifH) were detected in the three recA genotypes of R. anhuiense isolates that were closely related to those of the pea and faba rhizobia. This study clarified that R. anhuiense was the main symbiont for beach pea rhizobia on the seashore line of Shandong Peninsula. The low level genetic diversity of beach pea rhizobia revealed by both MLSA and the symbiotic genes might be related to the strong selection pressure produced by the saline–alkaline environment and the host plants.

Growth and Nutrient Status of Kayu Kuku [ Pericopsis mooniana (Thw.) Thw] with Mycorrhiza in Soil Media of Nickel Post Mining Site.

Arbuscular Mycorrhizal Fungi are categorized as phytoremediant and increase the tolerance of plants under condition of heavy metal pollution. Effectiveness of AMF is determined very much by species of AMF, plant species and environmental condition. Therefore, testing the effect of local AMF on growth and absorption of nutrients and metal by Pericopsis mooniana planting stocks in growing media which are heavily polluted by heavy metal, need to be conducted. There were testing of 6 inoculums of local AMF which were isolated from rhizosphere of P. mooniana, namely AMF from district of Kolaka (Lamedai Nature Reserve, Tanggetada Natural Forest, Bali Jaya Village Plantation Forest and PT. Vale Indonesia Tbk) and from Kendari town (Campus environment of Halu Oleo University and Office of Southeast Sulawesi Governor). Besides the 6 local AMF, there were treatment without AMF (control) and treatment with mycofer as comparison. Results showed that local AMF were effective in increasing growth and biomass of plants; absorption of C, N, P and K in three parts of the plants; Ca in stems and leaves and of Mg in leaf tissues; increasing formation of plant's root nodules and were able to reduce Ni content in tissues of kayu kuku planting stocks. Effects of local AMF from Lamedai nature reserve and AMF from PT. Vale Indonesia were greater as compared with those of mycofer IPB. Content of Ni in kayu kuku plant tissue was found more in roots as shown by the value of TF<1. Based on this study, kayu kuku is categorized as excluder species (TF<1) and moderate species toward Ni (>50 mg Ni/kg of plant dry weight) and possessed very high dependence on AMF (MIE >75%). Local AMF are potential to be developed as biological fertilizer to improve planting stocks for rehabilitation of degraded land.

A survey of the energy metabolism of nodulating symbionts reveals a new form of respiratory complex I.

A limiting factor in agriculture is the availability of nitrogen in the soil, which may be compensated by biological N2 fixation catalysed by bacteria. Most biological N2 fixation occurs in root nodules of plants that respond to bacterial infection by establishing symbiosis with selected prokaryotes. The plants provide energy metabolites and a microoxic environment to the bacterial symbionts to facilitate their capacity of N2 fixation. Despite enormous advances in the molecular genetics of this symbiosis between plants and nodulating bacteria, we still do not understand fundamental aspects which determine the efficiency of N2 fixation in the nodules, and therefore the capacity to biologically enrich agricultural soils. Here we provide an overview of the central features of the energy metabolism that sustains N2 fixation, with emphasis on the bacterial respiratory chain supplying the electrons and ATP required for the nitrogenase reaction. We discuss common trends and specific variations in the integrated process of respiratory electron transport and N2 fixation. Among such variations we introduce green complex I, an ancient version of NADH:ubiquinone oxidoreductase that is present in several Rhizobiaceae and may facilitate N2 fixation.

Isolation and purification of Rhizobium from French bean (Phaseolus vulgaris L.) root nodules

Six rhizobial isolates were collected from root nodules of Phaseolus vulgaris plants and isolates were designated as Rb1. the majority of the isolates were rapid growers within the medium and growth obtained on 3- 5 days of the incubation whereas a few of the isolates were slow growers and growth obtained on 3-4 days. Rhizobial colonies in Yeast Extract Mannitol Agar (YEMA) medium were round mucoid and white. Under microscopic examination, bacteria appeared as nonmotile, gram negative rod shaped. The Rhizobial isolates was characterized based on the growth behavior in the medium of Congo red, HoferâÂ�?Â�?s alkaline broth and polyhydroxy butyrate staining. All of these tests confirmed that findings of the present study have been isolated Rhizobium species.

The diversity of rhizobia nodulating the Medicago, Melilotus and Trigonella inoculation group in Egypt is marked by the dominance of two genetic types

Twenty four rhizobial strains were isolated from root nodules of Melilotus, Medicago and Trigonella plants growing wild in soils throughout Egypt. The nearly complete 16S rRNA gene sequence from each strain showed that 12 strains (50 %) were closely related to the Ensifer meliloti LMG6133T type strain with identity values higher than 99.0 %, that 9 (37.5 %) strains were more than 99 % identical to the E. medicae WSM419T type strain, and that 3 (12.5 %) strains showed 100 % identity with the type strain of N. huautlense S02T. Accordingly, the diversity of rhizobial strains nodulating wild Melilotus, Medicago and Trigonella species in Egypt is marked by predominance of two genetic types, E. meliloti and E. medicae, although the frequency of isolation was slightly higher in E. meliloti. Sequencing of the symbiotic nodC gene from selected Medicago and Melilotus strains revealed that they were all similar to those of the E. meliloti LMG6133T and E. medicae WSM419T type strains, respectively. Similarly, nodC sequences of strains identified as members of the genus Neorhizobium were more than 99 % identical to that of N. galegae symbiovar officinalis HAMBI 114.

Effect of fertility levels and biofertilizers on growth and yield of cowpea on sandy loam soil of Rajasthan

A field experiment was conducted during Kharif season of 2013 to know the effect of fertility levels and biofertilizers on growth and yield of cowpea on sandy loam soil of Rajasthan. The experiment consisted of four treatments of fertility levels (control, 100 % RDF, 75 % RDF+VC @ 2 t/ha and 100 % RDF+VC @ 2 t/ha) and four levels of biofertilizers (control, Rhizobium , PSB and Rhizobium + PSB) thereby making sixteen treatment combinations tested in factorial Randomized Block Design with three replications. Results indicated that application of 100 per cent RDF+VC @ 2 t/ha significantly increased the plant height, number of branches per plant, chlorophyll content, total root and effective root nodules, fresh weight and dry weight of nodules, leghaemoglobin content, number of pods per plant, number of seeds per pod, seed, straw and biological yield and remained at par with the application of 75 per cent RDF+VC @ 2 t/ha over control. However, application the test weight and harvest index unchanged under different fertility levels. Results further indicated that inoculation of Rhizobium and PSB significantly increased the chlorophyll content, total root and effective root nodules, fresh weight and dry weight of nodules, leghaemoglobin content, number of pods per plant, number of seeds per pod, seed and biological yield. However, inoculation of Rhizobium and PSB significantly increased the plant height, number of branches per plant and straw yield over the rest of treatments. However, the test weight and harvest index remained unchanged under different levels of biofertilizers.

What is the true nitrogenase reaction? A guided approach.

Only diazotrophic bacteria, called Rizhobia, living as symbionts in the root nodules of leguminous plants and certain free-living prokaryotic cells can fix atmospheric N2 . In these microorganisms, nitrogen fixation is carried out by the nitrogenase protein complex. However, the reduction of nitrogen to ammonia has an extremely high activation energy due to the stable (unreactive) N≡N triple bond. The structural and functional features of the nitrogenase protein complex, based on the stepwise transfer of eight electrons from reduced ferredoxin to the nitrogenase, coupled to the hydrolysis of 16 ATP molecules, to fix one N2 molecule into two NH3 molecules, is well understood. Yet, a number of different nitrogenase-catalyzed reactions are present in biochemistry textbooks, which might cause misinterpretation. In this article, we show that when trying to balance the reaction catalyzed by the nitrogenase protein complex, it is important to show explicitly the 16 H(+) released by the hydrolysis of the 16 ATP molecules needed to fix the atmospheric N2.

Genetic Characterization of Rhizobia Associated with Horse Gram [Macrotyloma uniflorum (Lam.) Verdc.] Based on RAPD and RFLP

Aim: To genetically characterize rhizobia collected from the root nodules of Horse gram plants grown in different soil samples by using the methods RAPD and RFLP. Place and Duration of Study: Root nodules were collected from the plants grown in soil samples collected from different regions in Andhra Pradesh and Telangana states, India. Methodology: These isolates were characterized by two RAPD primers RPO4 and RPO5 of 10 nucleotide length. The PCR amplicons were purified by Qiaquick® PCR purification kit and digested by three restriction endonucleases i.e., TaqI, HpaII and AluI. Results: The RAPD profiles and restriction analysis of 16S rRNA gene with the three Original Research Article Edulamudi et al.; BMRJ, 5(4): 339-350, 2015; Article no.BMRJ.2015.035 340 endonucleases showed high polymorphism. RAPD and RFLP analysis of these 32 horse gram rhizobia showed that these isolates fall into four major clusters. The first clusters of both dendrograms from RAPD and RFLP contained the majority of the rhizobial isolates. Conclusion: From this, it is clear that RAPD and RFLP may play an important role if applied, to know the genetic diversity of rhizobia. High genetic diversity was observed among the horse gram rhizobial population and very few of the bacteria were considered to be identical. It clearly shows that the horse gram rhizobia are phylogenetically distinct.

Genetic and Biochemical Characterization of Some Egyptian Rhizobia Isolates Nodulating Faba Bean

Ten Rhizobial isolates were isolated from root nodules of Faba bean plants (Viciae faba L.) grown in different soil types and representing different geographic locations in Egypt. The isolates were characterized biochemically for their production of eachIAA and catalase. The tested isolates differed in their IAA production. The maximum production of IAA production was recorded for RLZ isolate of Zefta with value of 4.56 μg/ml, while the lowest production was recorded for RLK isolate of Kaha with 2.04 μg/ml. Moreover, all isolates were positive in their production of Catalase enzyme except RLZ isolate. The isolates were evaluated for their plasmid content and profiles produced after cutting by two restriction endonucleases (EcoRI and MSPI). SDS-PAGE analysis was used to distinguish between the different isolates based on their banding protein patterns.

Antagonistic effect ofMesorhizobium ciceriIsolates onFusarium oxysporum F. Sp.Ciceri

A total of 207 wild type (WT) isolates of Mesorhizobium ciceri, isolated from root nodules of chickpea plants, was screened for antagonistic effect to Fusarium oxysporum f.sp. ciceri on TY medium by spot test method. Seven isolates (MC69, MC84, MC96, MC99, MC180, MC183 and MC190) were Nod+ and found to be antagonistic to Fusarium oxysporum f.sp. ciceri by showing inhibition zone, but none produced antibiotic or solubilize tricalcium phosphate. However, these produced indole acetic acid (IAA), which ranged from 200.2 mg/ml to 1762.7 mg/ml. Three isolates (MC84, MC96 and MC99) produced siderophore by making orange halo zone on blue coloured plates. The MC99 was found to be best antagonistic isolate as it produced the maximum amount of siderophore and IAA.

Effect of actinobacteria on Lotus tenuis – Mesorhizobium loti symbiosis: preliminary study

The effect of the actinobacteria on the legume Lotus tenuis, a model forage plant of the Flooding Pampa region in Argentina was to promote plant growth and root nodulation. L. tenuis seedlings were inoculated either with the symbiotic N2-fixing strain Mesorhizobium loti, or with saprophytic strain of Streptomyces MM40, Actinoplanes ME3, or Micromonospora MM18, or co-inoculated with a combination of one, two or three of them, together with the rhizobium. The plants were grown in pouches and fertilized with three nitrogen levels (low, medium and high). L. tenuis plants co-inoculated with the symbiotic M. loti and actinobacteria showed an increase in plant biomass and nodulation. Plants fertilized with high N levels (inhibitory for nodulation by M. loti) were nodulated if the M. loti strain was added simultaneously with actinobacteria. These preliminary results show that actinobacteria have potential agronomic application which should be further explored.

A term�kenys�get jav�t� bakt�riumos talajolt�s t�rt�neti �ttekint�se

The first bacteria capable of biological nitrogen-fixation and for this reason for the replacement of inorganic fertilizers was found in the root-nodules of leguminous plants more than 100 years ago. The other nitrogen-fixing bacteria, the associative azospirillums, on the other hand do not create visible systems, alterations in the root system. They were therefore found and reported only about 40 years ago. The isolated and identified bacteria are well-used in the agriculture since then, but still we can find unknown elements behind of their functioning. Nowadays second and third generations of microbial inoculums are applied. The soil-plant-microbe systems are so multifactorial arrangements, than there are several biotic and abiotic factors influencing of their real functioning. We should learn more how those systems are really working. The beneficial effects of those microbial inoculums will be discussed in this review with a historical background.

Reaction of the hemochromogen test with the heme protein leghemoglobin obtained from soybean root nodules

The hemochromogen test for blood relies on the reaction of pyridine with the heme group of hemoglobin. Leghemoglobin, a heme protein found in the root nodules of nitrogen fixing plants, has been tested in this paper for reactivity with the hemochromogen test. Root nodules from soybean plants were used for this testing due to their high leghemoglobin content. It was found that prepared extractions from soybean root nodules produced a positive reaction with the hemochromogen test; however, directly tested (non-extracted) root nodules produced negative hemochromogen test results. In addition, stains prepared from the root nodules on fabric did not react with the hemochromogen reagent in this study.

Ascorbic acid production in root, nodule and Enterobacter spp. (Gammaproteobacteria) isolated from root nodule of the legume Abrus precatorius L.

Abstract l -ascorbic acid is an antioxidant and plays a significant role to protect against activated form of O2 for N2 fixation in root nodules of legume plants. The root nodules of Abrus precatorius L. is found to contain higher amount of ascorbic acid, ascorbate peroxidase (EC1.11.1.11) and glucose than non-nodulated roots that are beneficial for nodule function. Two ascorbic acid producing symbiotic bacterial strains (A3CK and A7CK) were isolated from nodules of this plant and identified as Enterobacter spp. (Gammaproteobacteria) based on phenotypic characteristics and 16S rDNA sequence based molecular phylogenetic approach. The host may contribute part of nodular ascorbic acid and another part might be produced by Enterobacter spp., which plays important roles particularly facilitating root infection for nodulation, N2 fixation and delay nodule senescence. The host plant may induce the symbiont to produce ascorbic acid when necessary, which was confirmed by the ascorbic acid production ability of the symbionts in culture. The production of ascorbic acid by the symbiont increased largely when the Yeast Extract Mannitol medium was supplemented with fructose and ammonium sulfate in culture as carbon and nitrogen source. The symbionts also have some plant growth promoting traits viz. IAA production, N2 fixation, ACC deaminase activity etc. Few legume plants are reported where Gammaproteobacteria are found in root nodules. A. precatorius is another legume plant reported here where Gammaproteobacteria are found in root nodule and they possess the ability to produce ascorbic acid with some other PGPR traits beneficial for nodule function and plant growth promotion.

MALDI-MS-assisted molecular imaging of metabolites in legume plants.

Mass spectrometric imaging (MSI) is a powerful analytical tool that provides spatial information of several compounds in a single experiment. This technique has been used extensively to study proteins, peptides, and lipids, and is becoming more common for studying small molecules such as endogenous metabolites. With matrix-assisted laser desorption/ionization (MALDI)-MSI, spatial distributions of multiple metabolites can be simultaneously detected within a biological tissue section. Herein, we present a method developed specifically for imaging metabolites in legume plant roots and root nodules which can be adapted for studying metabolites in other legume organs and even other biological tissue samples. We focus on essential steps such as sample preparation and matrix application, comparing several useful techniques, and present a standard workflow that can be easily modified for different tissue types and instrumentation.