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Alharbi K, Rashwan E, Hafez E, Omara AED, Mohamed HH, Alshaal T. Potassium Humate and Plant Growth-Promoting Microbes Jointly Mitigate Water Deficit Stress in Soybean Cultivated in Salt-Affected Soil. PLANTS (BASEL, SWITZERLAND) 2022; 11:3016. [PMID: 36432745 PMCID: PMC9698740 DOI: 10.3390/plants11223016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 11/02/2022] [Accepted: 11/04/2022] [Indexed: 06/16/2023]
Abstract
Lack of high-quality irrigation water and soil salinity are two main environmental factors that affect plant development. When both stressors are combined, the soil becomes sterile and constrains plant productivity. Consequently, two field trials were designed to assess whether plant growth-promoting microbes (PGPMs; Bradyrhizobium japonicum (USDA 110) and Trichoderma harzianum) and potassium humate (K-humate) can stimulate soybean growth, productivity, and seed quality under two different watering regimes as follows: (i) well-watered (WW), where plants were irrigated at 12-day intervals (recommended), and (ii) water stress (WS), where plants were irrigated at the 18-day intervals in salt-affected soil during 2020 and 2021 seasons. Results revealed that coupled application of PGPMs and K-humate resulted in a substantial improvement in K+ levels in the leaves compared to Na+ levels, which has a direct positive impact on an enhancement in the antioxidants defense system (CAT, POX, SOD), which caused the decline of the oxidative stress indicators (H2O2, MDA, and EL%) as well as proline content under water stress in salt-affected soil. Hence, a significant increase in root length, nodule weight, soybean relative water content (RWC), stomatal conductance, photosynthetic pigments, net photosynthetic rate, soluble protein, seed carbohydrate content as well as the number of pods plant-1 and seed yield was reported. In conclusion, the combined application of PGPMs and K-humate might be recommended to maximize the soybean growth and productivity under harsh growth conditions (e.g., water stress and soil salinity).
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Affiliation(s)
- Khadiga Alharbi
- Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia
| | - Emadeldeen Rashwan
- Agronomy Department, Faculty of Agriculture, Tanta University, Tanta 31527, Egypt
| | - Emad Hafez
- Department of Agronomy, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt
| | - Alaa El-Dein Omara
- Agricultural Research Center, Microbiology, Soils, Water Environment Research Institute, Giza 12112, Egypt
| | - Hossam Hussein Mohamed
- Department of Agronomy, Faculty of Agriculture, Ain Shams University, Cairo 13625, Egypt
| | - Tarek Alshaal
- Soil and Water Department, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt
- Department of Applied Plant Biology, Institute of Crop Sciences, University of Debrecen, Böszörményi Street 138, 4032 Debrecen, Hungary
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2
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Tsurumaru H, Hashimoto S, Okizaki K, Kanesaki Y, Yoshikawa H, Yamakawa T. A Putative Type III Secretion System Effector Encoded by the MA20_12780 Gene in Bradyrhizobium japonicum Is-34 Causes Incompatibility with Rj4 Genotype Soybeans. Appl Environ Microbiol 2015; 81:5812-9. [PMID: 26092458 PMCID: PMC4551253 DOI: 10.1128/aem.00823-15] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 06/12/2015] [Indexed: 11/20/2022] Open
Abstract
The nodulation of Bradyrhizobium japonicum Is-34 is restricted by Rj4 genotype soybeans (Glycine max). To identify the genes responsible for this incompatibility, Tn5 mutants of B. japonicum Is-34 that were able to overcome this nodulation restriction were obtained. Analysis of the Tn5 mutants revealed that Tn5 was inserted into a region containing the MA20_12780 gene. In addition, direct disruption of this gene using marker exchange overcame the nodulation restriction by Rj4 genotype soybeans. The MA20_12780 gene has a tts box motif in its upstream region, indicating a possibility that this gene encodes a type III secretion system (T3SS) effector protein. Bioinformatic characterization revealed that the MA20_12780 protein contains the small ubiquitin-like modifier (SUMO) protease domain of the C48 peptidase (ubiquitin-like protease 1 [Ulp1]) family. The results of the present study indicate that a putative T3SS effector encoded by the MA20_12780 gene causes the incompatibility with Rj4 genotype soybeans, and they suggest the possibility that the nodulation restriction of B. japonicum Is-34 may be due to Rj4 genotype soybeans recognizing the putative T3SS effector (MA20_12780 protein) as a virulence factor.
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Affiliation(s)
- Hirohito Tsurumaru
- Graduate School of Life Science, Tohoku University, Miyagi, Japan Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Syougo Hashimoto
- Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Kouhei Okizaki
- Graduate School of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
| | - Yu Kanesaki
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan
| | - Hirofumi Yoshikawa
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo, Japan Department of Bioscience, Tokyo University of Agriculture, Tokyo, Japan
| | - Takeo Yamakawa
- Department of Biosciences and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
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3
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Iida T, Itakura M, Anda M, Sugawara M, Isawa T, Okubo T, Sato S, Chiba-Kakizaki K, Minamisawa K. Symbiosis island shuffling with abundant insertion sequences in the genomes of extra-slow-growing strains of soybean bradyrhizobia. Appl Environ Microbiol 2015; 81:4143-54. [PMID: 25862225 PMCID: PMC4524158 DOI: 10.1128/aem.00741-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 04/03/2015] [Indexed: 11/20/2022] Open
Abstract
Extra-slow-growing bradyrhizobia from root nodules of field-grown soybeans harbor abundant insertion sequences (ISs) and are termed highly reiterated sequence-possessing (HRS) strains. We analyzed the genome organization of HRS strains with the focus on IS distribution and symbiosis island structure. Using pulsed-field gel electrophoresis, we consistently detected several plasmids (0.07 to 0.4 Mb) in the HRS strains (NK5, NK6, USDA135, 2281, USDA123, and T2), whereas no plasmids were detected in the non-HRS strain USDA110. The chromosomes of the six HRS strains (9.7 to 10.7 Mb) were larger than that of USDA110 (9.1 Mb). Using MiSeq sequences of 6 HRS and 17 non-HRS strains mapped to the USDA110 genome, we found that the copy numbers of ISRj1, ISRj2, ISFK1, IS1632, ISB27, ISBj8, and IS1631 were markedly higher in HRS strains. Whole-genome sequencing showed that the HRS strain NK6 had four small plasmids (136 to 212 kb) and a large chromosome (9,780 kb). Strong colinearity was found between 7.4-Mb core regions of the NK6 and USDA110 chromosomes. USDA110 symbiosis islands corresponded mainly to five small regions (S1 to S5) within two variable regions, V1 (0.8 Mb) and V2 (1.6 Mb), of the NK6 chromosome. The USDA110 nif gene cluster (nifDKENXSBZHQW-fixBCX) was split into two regions, S2 and S3, where ISRj1-mediated rearrangement occurred between nifS and nifB. ISs were also scattered in NK6 core regions, and ISRj1 insertion often disrupted some genes important for survival and environmental responses. These results suggest that HRS strains of soybean bradyrhizobia were subjected to IS-mediated symbiosis island shuffling and core genome degradation.
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Affiliation(s)
- Takayuki Iida
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Manabu Itakura
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Mizue Anda
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | | | - Tsuyoshi Isawa
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Takashi Okubo
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Shusei Sato
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
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Dao TV, Nomura M, Hamaguchi R, Kato K, Itakura M, Minamisawa K, Sinsuwongwat S, Le HTP, Kaneko T, Tabata S, Tajima S. NAD-Malic Enzyme Affects Nitrogen Fixing Activity of Bradyrhizobium japonicum USDA 110 Bacteroids in Soybean Nodules. Microbes Environ 2012; 23:215-20. [PMID: 21558711 DOI: 10.1264/jsme2.23.215] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The NAD(+)-dependent malic enzyme (DME) has been reported to play a key role supporting nitrogenase activity in bacteroids of Sinorhizobium meliloti. Genetic evidence for a similar role in Bradyrhizobium japonicum USDA110 was obtained by constructing a dme mutant. Soybean plants inoculated with a dme mutant did not show delayed nodulation, but formed small root nodules and exhibited significant nitrogen-deficiency symptoms. Nodule numbers and the acetylene reducting activity per nodule as a dry weight value 14 and 28 days after inoculation with the dme mutant were comparable to those of plants inoculated with wild-type B. japonicum. However, shoot dry weight and acetylene reducting activity per nodule decreased to ca. 30% of the values in plants with wild-type B. japonicum. The sucrose and organic acid (malate, succinate, acetate, α-ketoglutarate and lactate) contents of the nodules were investigated. Amounts of sucrose, malate and a-ketoglutarate increased on inoculation with the dme mutant, suggesting that the decreased DME and nitrogenase activities in the bacteroids resulted in a reduction in the consumption of these respiratory metabolites by the nodules. The data suggest that the DME activity of B. japonicum bacteroids plays a role in nodule metabolism and supports nitrogen fixation.
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Affiliation(s)
- Tan Van Dao
- Centre for Ressources and Environmental Studies, Vietnam National University
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5
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Sameshima-Saito R, Chiba K, Hirayama J, Itakura M, Mitsui H, Eda S, Minamisawa K. Symbiotic Bradyrhizobium japonicum reduces N2O surrounding the soybean root system via nitrous oxide reductase. Appl Environ Microbiol 2006; 72:2526-32. [PMID: 16597953 PMCID: PMC1449076 DOI: 10.1128/aem.72.4.2526-2532.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2005] [Accepted: 01/25/2006] [Indexed: 11/20/2022] Open
Abstract
N(2)O reductase activity in soybean nodules formed with Bradyrhizobium japonicum was evaluated from N(2)O uptake and conversion of (15)N-N(2)O into (15)N-N(2). Free-living cells of USDA110 showed N(2)O reductase activity, whereas a nosZ mutant did not. Complementation of the nosZ mutant with two cosmids containing the nosRZDFYLX genes of B. japonicum USDA110 restored the N(2)O reductase activity. When detached soybean nodules formed with USDA110 were fed with (15)N-N(2)O, they rapidly emitted (15)N-N(2) outside the nodules at a ratio of 98.5% of (15)N-N(2)O uptake, but nodules inoculated with the nosZ mutant did not. Surprisingly, N(2)O uptake by soybean roots nodulated with USDA110 was observed even in ambient air containing a low concentration of N(2)O (0.34 ppm). These results indicate that the conversion of N(2)O to N(2) depends exclusively on the respiratory N(2)O reductase and that soybean roots nodulated with B. japonicum carrying the nos genes are able to remove very low concentrations of N(2)O.
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Affiliation(s)
- Reiko Sameshima-Saito
- Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan
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6
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You M, Nishiguchi T, Saito A, Isawa T, Mitsui H, Minamisawa K. Expression of the nifH gene of a Herbaspirillum endophyte in wild rice species: daily rhythm during the light-dark cycle. Appl Environ Microbiol 2006; 71:8183-90. [PMID: 16332801 PMCID: PMC1317309 DOI: 10.1128/aem.71.12.8183-8190.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The expression of nitrogenase genes of Herbaspirillum sp. B501 associated in shoot (leaf and stem) of wild rice, Oryza officinalis, was studied by means of reverse transcription-PCR (RT-PCR) targeted at the nifH gene. RT-PCR analyses indicate that nifH transcript was detected exclusively from nitrogen-fixing cells of gfp-tagged strain B501gfp1 in both free-living and endophytic states by using a constitutive gfp gene transcript as a positive control. Transcription of nifH and nitrogen fixation in free-living cells were induced maximally at a 2% O2 concentration and repressed in free air (21% O2). nifH transcription was monitored in the endophytic cells by using total RNA extracted from B501gfp1-inoculated wild rice plants during daily light-dark cycles. The level of nifH transcription in planta varied dramatically, with a maximum during the light period. Moreover, the light radiation enhanced nifH expression even in free-living cells grown in culture. These results suggest that in planta nitrogen fixation by the endophyte shows a daily rhythm determined by the plant's light environment.
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Affiliation(s)
- Mu You
- Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan
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7
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Sameshima-Saito R, Chiba K, Minamisawa K. Correlation of Denitrifying Capability with the Existence of nap, nir, nor and nos Genes in Diverse Strains of Soybean Bradyrhizobia. Microbes Environ 2006. [DOI: 10.1264/jsme2.21.174] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
| | - Kaori Chiba
- Graduate School of Life Sciences, Tohoku University
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8
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Sameshima-Saito R, Chiba K, Minamisawa K. New method of denitrification analysis of bradyrhizobium field isolates by gas chromatographic determination of (15)N-labeled N(2). Appl Environ Microbiol 2004; 70:2886-91. [PMID: 15128547 PMCID: PMC404451 DOI: 10.1128/aem.70.5.2886-2891.2004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2003] [Accepted: 01/22/2004] [Indexed: 11/20/2022] Open
Abstract
To evaluate the denitrification abilities of many Bradyrhizobium field isolates, we developed a new (15)N-labeled N(2) detection methodology, which is free from interference from atmospheric N(2) contamination. (30)N(2) ((15)N(15)N) and (29)N(2) ((15)N(14)N) were detected as an apparent peak by a gas chromatograph equipped with a thermal conductivity detector with N(2) gas having natural abundance of (15)N (0.366 atom%) as a carrier gas. The detection limit was 0.04% (30)N(2), and the linearity extended at least to 40% (30)N(2). When Bradyrhizobium japonicum USDA110 was grown in cultures anaerobically with (15)NO(3)(-), denitrification product ((30)N(2)) was detected stoichiometrically. A total of 65 isolates of soybean bradyrhizobia from two field sites in Japan were assayed by this method. The denitrification abilities were partly correlated with filed sites, Bradyrhizobium species, and the hup genotype.
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Affiliation(s)
- Reiko Sameshima-Saito
- Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan
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9
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Bartosik D, Sochacka M, Baj J. Identification and characterization of transposable elements of Paracoccus pantotrophus. J Bacteriol 2003; 185:3753-63. [PMID: 12813068 PMCID: PMC161580 DOI: 10.1128/jb.185.13.3753-3763.2003] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We studied diversity and distribution of transposable elements residing in different strains (DSM 11072, DSM 11073, DSM 65, and LMD 82.5) of a soil bacterium Paracoccus pantotrophus (alpha-Proteobacteria). With application of a shuttle entrapment vector pMEC1, several novel insertion sequences (ISs) and transposons (Tns) have been identified. They were sequenced and subjected to detailed comparative analysis, which allowed their characterization (i.e., identification of transposase genes, terminal inverted repeats, as well as target sequences) and classification into the appropriate IS or Tn families. The frequency of transposition of these elements varied and ranged from 10(-6) to 10(-3) depending on the strain. The copy number, localization (plasmid or chromosome), and distribution of these elements in the Paracoccus species P. pantotrophus, P. denitrificans, P. methylutens, P. solventivorans, and P. versutus were analyzed. This allowed us to distinguish elements that are common in paracocci (ISPpa2, ISPpa3--both of the IS5 family--and ISPpa5 of IS66 family) as well as strain-specific ones (ISPpa1 of the IS256 family, ISPpa4 of the IS5 family, and Tn3434 and Tn5393 of the Tn3 family), acquired by lateral transfer events. These elements will be of a great value in the design of new genetic tools for paracocci, since only one element (IS1248 of P. denitrificans) has been described so far in this genus.
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Affiliation(s)
- Dariusz Bartosik
- Warsaw University, Institute of Microbiology, Department of Bacterial Genetics, 02-096 Warsaw, Poland.
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Phylogeny and distribution of extra-slow-growing Bradyrhizobium japonicum harboring high copy numbers of RSα, RSβ and IS1631. FEMS Microbiol Ecol 2003; 44:191-202. [DOI: 10.1016/s0168-6496(03)00009-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Johnson GR, Jain RK, Spain JC. Origins of the 2,4-dinitrotoluene pathway. J Bacteriol 2002; 184:4219-32. [PMID: 12107140 PMCID: PMC135200 DOI: 10.1128/jb.184.15.4219-4232.2002] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2002] [Accepted: 05/06/2002] [Indexed: 11/20/2022] Open
Abstract
The degradation of synthetic compounds requires bacteria to recruit and adapt enzymes from pathways for naturally occurring compounds. Previous work defined the steps in 2,4-dinitrotoluene (2,4-DNT) metabolism through the ring fission reaction. The results presented here characterize subsequent steps in the pathway that yield the central metabolic intermediates pyruvate and propionyl coenzyme A (CoA). The genes encoding the degradative pathway were identified within a 27-kb region of DNA cloned from Burkholderia cepacia R34, a strain that grows using 2,4-DNT as a sole carbon, energy, and nitrogen source. Genes for the lower pathway in 2,4-DNT degradation were found downstream from dntD, the gene encoding the extradiol ring fission enzyme of the pathway. The region includes genes encoding a CoA-dependent methylmalonate semialdehyde dehydrogenase (dntE), a putative NADH-dependent dehydrogenase (ORF13), and a bifunctional isomerase/hydrolase (dntG). Results from analysis of the gene sequence, reverse transcriptase PCR, and enzyme assays indicated that dntD dntE ORF13 dntG composes an operon that encodes the lower pathway. Additional genes that were uncovered encode the 2,4-DNT dioxygenase (dntAaAbAcAd), methylnitrocatechol monooxygenase (dntB), a putative LysR-type transcriptional (ORF12) regulator, an intradiol ring cleavage enzyme (ORF3), a maleylacetate reductase (ORF10), a complete ABC transport complex (ORF5 to ORF8), a putative methyl-accepting chemoreceptor protein (ORF11), and remnants from two transposable elements. Some of the additional gene products might play as-yet-undefined roles in 2,4-DNT degradation; others appear to remain from recruitment of the neighboring genes. The presence of the transposon remnants and vestigial genes suggests that the pathway for 2,4-DNT degradation evolved relatively recently because the extraneous elements have not been eliminated from the region.
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Affiliation(s)
- Glenn R Johnson
- Air Force Research Laboratory, U.S. Air Force, Tyndall Air Force Base, Florida 32403, USA
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Minamisawa K, Itakura M, Suzuki M, Ichige K, Isawa T, Yuhashi KI, Mitsui H. Horizontal Transfer of Nodulation Genes in Soils and Microcosms from Bradyrhizobium japonicum to B. elkanii. Microbes Environ 2002. [DOI: 10.1264/jsme2.2002.82] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
| | | | | | | | - Tsuyoshi Isawa
- Graduate School of Life Sciences, Tohoku University
- School of Agriculture, Ibaraki University
| | - Ken-ichi Yuhashi
- Graduate School of Life Sciences, Tohoku University
- School of Agriculture, Ibaraki University
- Plant Biotechnology Institute, Ibaraki Agriculture Center
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13
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Yasuta T, Okazaki S, Mitsui H, Yuhashi K, Ezura H, Minamisawa K. DNA sequence and mutational analysis of rhizobitoxine biosynthesis genes in Bradyrhizobium elkanii. Appl Environ Microbiol 2001; 67:4999-5009. [PMID: 11679318 PMCID: PMC93263 DOI: 10.1128/aem.67.11.4999-5009.2001] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We cloned and sequenced a cluster of genes involved in the biosynthesis of rhizobitoxine, a nodulation enhancer produced by Bradyrhizobium elkanii. The nucleotide sequence of the cloned 28.4-kb DNA region encompassing rtxA showed that several open reading frames (ORFs) were located downstream of rtxA. A large-deletion mutant of B. elkanii, USDA94 Delta rtx::Omega 1, which lacks rtxA, ORF1 (rtxC), ORF2, and ORF3, did not produce rhizobitoxine, dihydrorhizobitoxine, or serinol. The broad-host-range cosmid pLAFR1, which contains rtxA and these ORFs, complemented rhizobitoxine production in USDA94 Delta rtx::Omega 1. Further complementation experiments involving cosmid derivatives obtained by random mutagenesis with a kanamycin cassette revealed that at least rtxA and rtxC are necessary for rhizobitoxine production. Insertional mutagenesis of the N-terminal and C-terminal regions of rtxA indicated that rtxA is responsible for two crucial steps, serinol formation and dihydrorhizobitoxine biosynthesis. An insertional mutant of rtxC produced serinol and dihydrorhizobitoxine but no rhizobitoxine. Moreover, the rtxC product was highly homologous to the fatty acid desaturase of Pseudomonas syringae and included the copper-binding signature and eight histidine residues conserved in membrane-bound desaturase. This result suggested that rtxC encodes dihydrorhizobitoxine desaturase for the final step of rhizobitoxine production. In light of results from DNA sequence comparison, gene disruption experiments, and dihydrorhizobitoxine production from various substrates, we discuss the biosynthetic pathway of rhizobitoxine and its evolutionary significance in bradyrhizobia.
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Affiliation(s)
- T Yasuta
- Institute of Genetic Ecology, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan
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Yuhashi K, Ichikawa N, Ezura H, Akao S, Minakawa Y, Nukui N, Yasuta T, Minamisawa K. Rhizobitoxine production by Bradyrhizobium elkanii enhances nodulation and competitiveness on Macroptilium atropurpureum. Appl Environ Microbiol 2000; 66:2658-63. [PMID: 10831453 PMCID: PMC110596 DOI: 10.1128/aem.66.6.2658-2663.2000] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Application of 1-aminoocyclopropane-1-carboxylic acid, an ethylene precursor, decreased nodulation of Macroptilium atropurpureum by Bradyrhizobium elkanii. B. elkanii produces rhizobitoxine, an ethylene synthesis inhibitor. Elimination of rhizobitoxine production in B. elkanii increased ethylene evolution and decreased nodulation and competitiveness on M. atropurpureum. These results suggest that rhizobitoxine enhances nodulation and competitiveness of B. elkanii on M. atropurpureum.
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Affiliation(s)
- K Yuhashi
- Institute of Genetic Ecology, Tohoku University, Katahira, Aoba-ku, Sendai, 980-8577, Japan
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