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Ni H, Hou X, Tian S, Liu C, Zhang G, Peng Y, Chen L, Wang J, Chen Q, Xin D. Insights into the Early Steps of the Symbiotic Interaction between Soybean ( Glycine max) and Sinorhizobium fredii Symbiosis Using Transcriptome, Small RNA, and Degradome Sequencing. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:17084-17098. [PMID: 39013023 PMCID: PMC11299180 DOI: 10.1021/acs.jafc.4c02312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 06/26/2024] [Accepted: 06/27/2024] [Indexed: 07/18/2024]
Abstract
Symbiotic nitrogen fixation carried out by the soybean-rhizobia symbiosis increases soybean yield and reduces the amount of nitrogen fertilizer that has been applied. MicroRNAs (miRNAs) are crucial in plant growth and development, prompting an investigation into their role in the symbiotic interaction of soybean with partner rhizobia. Through integrated small RNA, transcriptome, and degradome sequencing analysis, 1215 known miRNAs, 314 of them conserved, and 187 novel miRNAs were identified, with 44 differentially expressed miRNAs in soybean roots inoculated with Sinorhizobium fredii HH103 and a ttsI mutant. The study unveiled that the known miRNA gma-MIR398a-p5 was downregulated in the presence of the ttsI mutation, while the target gene of gma-MIR398a-p5, Glyma.06G007500, associated with nitrogen metabolism, was upregulated. The results of this study offer insights for breeding high-efficiency nitrogen-fixing soybean varieties, enhancing crop yield and quality.
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Affiliation(s)
| | | | - Siyi Tian
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
| | - Chunyan Liu
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
| | - Guoqing Zhang
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
| | - Yang Peng
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
| | - Lin Chen
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
| | - Jinhui Wang
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
| | - Qingshan Chen
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
| | - Dawei Xin
- Key Laboratory of Soybean
Biology of the Chinese Ministry of Education, Key Laboratory of Soybean
Biology and Breeding, Genetics of Chinese Agriculture Ministry, College
of Agriculture, Northeast Agricultural University, Harbin 150036, China
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Adaptive Evolution of Rhizobial Symbiosis beyond Horizontal Gene Transfer: From Genome Innovation to Regulation Reconstruction. Genes (Basel) 2023; 14:genes14020274. [PMID: 36833201 PMCID: PMC9957244 DOI: 10.3390/genes14020274] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
There are ubiquitous variations in symbiotic performance of different rhizobial strains associated with the same legume host in agricultural practices. This is due to polymorphisms of symbiosis genes and/or largely unexplored variations in integration efficiency of symbiotic function. Here, we reviewed cumulative evidence on integration mechanisms of symbiosis genes. Experimental evolution, in concert with reverse genetic studies based on pangenomics, suggests that gain of the same circuit of key symbiosis genes through horizontal gene transfer is necessary but sometimes insufficient for bacteria to establish an effective symbiosis with legumes. An intact genomic background of the recipient may not support the proper expression or functioning of newly acquired key symbiosis genes. Further adaptive evolution, through genome innovation and reconstruction of regulation networks, may confer the recipient of nascent nodulation and nitrogen fixation ability. Other accessory genes, either co-transferred with key symbiosis genes or stochastically transferred, may provide the recipient with additional adaptability in ever-fluctuating host and soil niches. Successful integrations of these accessory genes with the rewired core network, regarding both symbiotic and edaphic fitness, can optimize symbiotic efficiency in various natural and agricultural ecosystems. This progress also sheds light on the development of elite rhizobial inoculants using synthetic biology procedures.
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Ghantasala S, Roy Choudhury S. Nod factor perception: an integrative view of molecular communication during legume symbiosis. PLANT MOLECULAR BIOLOGY 2022; 110:485-509. [PMID: 36040570 DOI: 10.1007/s11103-022-01307-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 07/27/2022] [Indexed: 06/15/2023]
Abstract
Compatible interaction between rhizobial Nod factors and host receptors enables initial recognition and signaling events during legume-rhizobia symbiosis. Molecular communication is a new paradigm of information relay, which uses chemical signals or molecules as dialogues for communication and has been witnessed in prokaryotes, plants as well as in animal kingdom. Understanding this fascinating relay of signals between plants and rhizobia during the establishment of a synergistic relationship for biological nitrogen fixation represents one of the hotspots in plant biology research. Predominantly, their interaction is initiated by flavonoids exuding from plant roots, which provokes changes in the expression profile of rhizobial genes. Compatible interactions promote the secretion of Nod factors (NFs) from rhizobia, which are recognised by cognate host receptors. Perception of NFs by host receptors initiates the symbiosis and ultimately leads to the accommodation of rhizobia within root nodules via a series of mutual exchange of signals. This review elucidates the bacterial and plant perspectives during the early stages of symbiosis, explicitly emphasizing the significance of NFs and their cognate NF receptors.
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Affiliation(s)
- Swathi Ghantasala
- Department of Biology, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh, 517507, India
| | - Swarup Roy Choudhury
- Department of Biology, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh, 517507, India.
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Eardly B, Meor Osman WA, Ardley J, Zandberg J, Gollagher M, van Berkum P, Elia P, Marinova D, Seshadri R, Reddy TBK, Ivanova N, Pati A, Woyke T, Kyrpides N, Loedolff M, Laird DW, Reeve W. The Genome of the Acid Soil-Adapted Strain Rhizobium favelukesii OR191 Encodes Determinants for Effective Symbiotic Interaction With Both an Inverted Repeat Lacking Clade and a Phaseoloid Legume Host. Front Microbiol 2022; 13:735911. [PMID: 35495676 PMCID: PMC9048898 DOI: 10.3389/fmicb.2022.735911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Accepted: 02/10/2022] [Indexed: 11/15/2022] Open
Abstract
Although Medicago sativa forms highly effective symbioses with the comparatively acid-sensitive genus Ensifer, its introduction into acid soils appears to have selected for symbiotic interactions with acid-tolerant R. favelukesii strains. Rhizobium favelukesii has the unusual ability of being able to nodulate and fix nitrogen, albeit sub-optimally, not only with M. sativa but also with the promiscuous host Phaseolus vulgaris. Here we describe the genome of R. favelukesii OR191 and genomic features important for the symbiotic interaction with both of these hosts. The OR191 draft genome contained acid adaptation loci, including the highly acid-inducible lpiA/acvB operon and olsC, required for production of lysine- and ornithine-containing membrane lipids, respectively. The olsC gene was also present in other acid-tolerant Rhizobium strains but absent from the more acid-sensitive Ensifer microsymbionts. The OR191 symbiotic genes were in general more closely related to those found in Medicago microsymbionts. OR191 contained the nodA, nodEF, nodHPQ, and nodL genes for synthesis of polyunsaturated, sulfated and acetylated Nod factors that are important for symbiosis with Medicago, but contained a truncated nodG, which may decrease nodulation efficiency with M. sativa. OR191 contained an E. meliloti type BacA, which has been shown to specifically protect Ensifer microsymbionts from Medicago nodule-specific cysteine-rich peptides. The nitrogen fixation genes nifQWZS were present in OR191 and P. vulgaris microsymbionts but absent from E. meliloti-Medicago microsymbionts. The ability of OR191 to nodulate and fix nitrogen symbiotically with P. vulgaris indicates that this host has less stringent requirements for nodulation than M. sativa but may need rhizobial strains that possess nifQWZS for N2-fixation to occur. OR191 possessed the exo genes required for the biosynthesis of succinoglycan, which is required for the Ensifer-Medicago symbiosis. However, 1H-NMR spectra revealed that, in the conditions tested, OR191 exopolysaccharide did not contain a succinyl substituent but instead contained a 3-hydroxybutyrate moiety, which may affect its symbiotic performance with Medicago hosts. These findings provide a foundation for the genetic basis of nodulation requirements and symbiotic effectiveness with different hosts.
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Affiliation(s)
- Bertrand Eardly
- Berks College, Penn State University, Reading, PA, United States
| | - Wan Adnawani Meor Osman
- Centre for Crop and Food Innovation, College of Science, Health, Engineering and Education, Food Futures Institute, Murdoch University, Murdoch, WA, Australia
| | - Julie Ardley
- Centre for Crop and Food Innovation, College of Science, Health, Engineering and Education, Food Futures Institute, Murdoch University, Murdoch, WA, Australia
| | - Jaco Zandberg
- Centre for Crop and Food Innovation, College of Science, Health, Engineering and Education, Food Futures Institute, Murdoch University, Murdoch, WA, Australia
| | - Margaret Gollagher
- Murdoch University Associate, Murdoch, WA, Australia.,Sustainability and Biosecurity, Department of Primary Industries and Regional Development, South Perth, WA, Australia
| | - Peter van Berkum
- Soybean Genomics and Improvement Laboratory, United States Department of Agriculture, Beltsville, MD, United States
| | - Patrick Elia
- Soybean Genomics and Improvement Laboratory, United States Department of Agriculture, Beltsville, MD, United States
| | - Dora Marinova
- Curtin University Sustainability Policy Institute, Curtin University, Bentley, WA, Australia
| | - Rekha Seshadri
- Department of Energy (DOE) Joint Genome Institute, Berkeley, CA, United States
| | - T B K Reddy
- Department of Energy (DOE) Joint Genome Institute, Berkeley, CA, United States
| | - Natalia Ivanova
- Department of Energy (DOE) Joint Genome Institute, Berkeley, CA, United States
| | - Amrita Pati
- Department of Energy (DOE) Joint Genome Institute, Berkeley, CA, United States
| | - Tanja Woyke
- Department of Energy (DOE) Joint Genome Institute, Berkeley, CA, United States
| | - Nikos Kyrpides
- Department of Energy (DOE) Joint Genome Institute, Berkeley, CA, United States
| | - Matthys Loedolff
- Centre for Crop and Food Innovation, College of Science, Health, Engineering and Education, Food Futures Institute, Murdoch University, Murdoch, WA, Australia
| | - Damian W Laird
- Centre for Water Energy and Waste, Harry Butler Institute, Murdoch University, Murdoch, WA, Australia
| | - Wayne Reeve
- Centre for Crop and Food Innovation, College of Science, Health, Engineering and Education, Food Futures Institute, Murdoch University, Murdoch, WA, Australia
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Kinetic proofreading of lipochitooligosaccharides determines signal activation of symbiotic plant receptors. Proc Natl Acad Sci U S A 2021; 118:2111031118. [PMID: 34716271 PMCID: PMC8612216 DOI: 10.1073/pnas.2111031118] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/21/2021] [Indexed: 01/31/2023] Open
Abstract
Plants and animals use cell surface receptors to sense and interpret environmental signals. In legume symbiosis with nitrogen-fixing bacteria, the specific recognition of bacterial lipochitooligosaccharide (LCO) signals by single-pass transmembrane receptor kinases determines compatibility. Here, we determine the structural basis for LCO perception from the crystal structures of two lysin motif receptor ectodomains and identify a hydrophobic patch in the binding site essential for LCO recognition and symbiotic function. We show that the receptor monitors the composition of the amphiphilic LCO molecules and uses kinetic proofreading to control receptor activation and signaling specificity. We demonstrate engineering of the LCO binding site to fine-tune ligand selectivity and correct binding kinetics required for activation of symbiotic signaling in plants. Finally, the hydrophobic patch is found to be a conserved structural signature in this class of LCO receptors across legumes that can be used for in silico predictions. Our results provide insights into the mechanism of cell-surface receptor activation by kinetic proofreading of ligands and highlight the potential in receptor engineering to capture benefits in plant-microbe interactions.
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Minimal gene set from Sinorhizobium ( Ensifer) meliloti pSymA required for efficient symbiosis with Medicago. Proc Natl Acad Sci U S A 2021; 118:2018015118. [PMID: 33384333 DOI: 10.1073/pnas.2018015118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Reduction of N2 gas to ammonia in legume root nodules is a key component of sustainable agricultural systems. Root nodules are the result of a symbiosis between leguminous plants and bacteria called rhizobia. Both symbiotic partners play active roles in establishing successful symbiosis and nitrogen fixation: while root nodule development is mostly controlled by the plant, the rhizobia induce nodule formation, invade, and perform N2 fixation once inside the plant cells. Many bacterial genes involved in the rhizobia-legume symbiosis are known, and there is much interest in engineering the symbiosis to include major nonlegume crops such as corn, wheat, and rice. We sought to identify and combine a minimal bacterial gene complement necessary and sufficient for symbiosis. We analyzed a model rhizobium, Sinorhizobium (Ensifer) meliloti, using a background strain in which the 1.35-Mb symbiotic megaplasmid pSymA was removed. Three regions representing 162 kb of pSymA were sufficient to recover a complete N2-fixing symbiosis with alfalfa, and a targeted assembly of this gene complement achieved high levels of symbiotic N2 fixation. The resulting gene set contained just 58 of 1,290 pSymA protein-coding genes. To generate a platform for future synthetic manipulation, the minimal symbiotic genes were reorganized into three discrete nod, nif, and fix modules. These constructs will facilitate directed studies toward expanding the symbiosis to other plant partners. They also enable forward-type approaches to identifying genetic components that may not be essential for symbiosis, but which modulate the rhizobium's competitiveness for nodulation and the effectiveness of particular rhizobia-plant symbioses.
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Rhizobium leguminosarum bv. trifolii NodD2 Enhances Competitive Nodule Colonization in the Clover-Rhizobium Symbiosis. Appl Environ Microbiol 2020; 86:AEM.01268-20. [PMID: 32651206 DOI: 10.1128/aem.01268-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 07/02/2020] [Indexed: 01/01/2023] Open
Abstract
Establishment of the symbiotic relationship that develops between rhizobia and their legume hosts is contingent upon an interkingdom signal exchange. In response to host legume flavonoids, NodD proteins from compatible rhizobia activate expression of nodulation genes that produce lipochitin oligosaccharide signaling molecules known as Nod factors. Root nodule formation commences upon legume recognition of compatible Nod factor. Rhizobium leguminosarum was previously considered to contain one copy of nodD; here, we show that some strains of the Trifolium (clover) microsymbiont R. leguminosarum bv. trifolii contain a second copy designated nodD2. nodD2 genes were present in 8 out of 13 strains of R. leguminosarum bv. trifolii, but were absent from the genomes of 16 R. leguminosarum bv. viciae strains. Analysis of single and double nodD1 and nodD2 mutants in R. leguminosarum bv. trifolii strain TA1 revealed that NodD2 was functional and enhanced nodule colonization competitiveness. However, NodD1 showed significantly greater capacity to induce nod gene expression and infection thread formation. Clover species are either annual or perennial and this phenological distinction is rarely crossed by individual R. leguminosarum bv. trifolii microsymbionts for effective symbiosis. Of 13 strains with genome sequences available, 7 of the 8 effective microsymbionts of perennial hosts contained nodD2, whereas the 3 microsymbionts of annual hosts did not. We hypothesize that NodD2 inducer recognition differs from NodD1, and NodD2 functions to enhance competition and effective symbiosis, which may discriminate in favor of perennial hosts.IMPORTANCE Establishment of the rhizobium-legume symbiosis requires a highly specific and complex signal exchange between both participants. Rhizobia perceive legume flavonoid compounds through LysR-type NodD regulators. Often, rhizobia encode multiple copies of nodD, which is one determinant of host specificity. In some species of rhizobia, the presence of multiple copies of NodD extends their symbiotic host-range. Here, we identified and characterized a second copy of nodD present in some strains of the clover microsymbiont Rhizobium leguminosarum bv. trifolii. The second nodD gene contributed to the competitive ability of the strain on white clover, an important forage legume. A screen for strains containing nodD2 could be utilized as one criterion to select strains with enhanced competitive ability for use as inoculants for pasture production.
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Wippel K, Long SR. Symbiotic Performance of Sinorhizobium meliloti Lacking ppGpp Depends on the Medicago Host Species. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2019; 32:717-728. [PMID: 30576265 DOI: 10.1094/mpmi-11-18-0306-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Host specificity in the root-nodule symbiosis between legumes and rhizobia is crucial for the establishment of a successful interaction and ammonia provision to the plant. The specificity is mediated by plant-bacterial signal exchange during early stages of interaction. We observed that a Sinorhizobium meliloti mutant ∆relA, which is deficient in initiating the bacterial stringent response, fails to nodulate Medicago sativa (alfalfa) but successfully infects Medicago truncatula. We used biochemical, histological, transcriptomic, and imaging approaches to compare the behavior of the S. meliloti ∆relA mutant and wild type (WT) on the two plant hosts. ∆relA performed almost WT-like on M. truncatula, except for reduced nitrogen-fixation capacity and a disorganized positioning of bacteroids within nodule cells. In contrast, ∆relA showed impaired root colonization on alfalfa and failed to infect nodule primordia. Global transcriptome analyses of ∆relA cells treated with the alfalfa flavonoid luteolin and of mature nodules induced by the mutant on M. truncatula revealed normal nod gene expression but overexpression of exopolysaccharide biosynthesis genes and a slight suppression of plant defense-like reactions. Many RelA-dependent transcripts overlap with the hypo-osmolarity-related FeuP regulon or are characteristic of stress responses. Based on our findings, we suggest that RelA is not essential until the late stages of symbiosis with M. truncatula, in which it may be involved in processes that optimize nitrogen fixation.
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Affiliation(s)
- Kathrin Wippel
- Department of Biology, Stanford University, Stanford, CA 94305, U.S.A
| | - Sharon R Long
- Department of Biology, Stanford University, Stanford, CA 94305, U.S.A
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Bashandy SR, Abd‐Alla MH, Bagy MMK. Biological Nitrogen Fixation and Biofertilizers as Ideal Potential Solutions for Sustainable Agriculture. INTEGRATING GREEN CHEMISTRY AND SUSTAINABLE ENGINEERING 2019:343-396. [DOI: 10.1002/9781119509868.ch12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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10
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Osman WAM, van Berkum P, León-Barrios M, Velázquez E, Elia P, Tian R, Ardley J, Gollagher M, Seshadri R, Reddy TBK, Ivanova N, Woyke T, Pati A, Markowitz V, Baeshen MN, Baeshen NN, Kyrpides N, Reeve W. High-quality draft genome sequence of Ensifer meliloti Mlalz-1, a microsymbiont of Medicago laciniata (L.) miller collected in Lanzarote, Canary Islands, Spain. Stand Genomic Sci 2017; 12:58. [PMID: 28975015 PMCID: PMC5613336 DOI: 10.1186/s40793-017-0270-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 09/14/2017] [Indexed: 11/26/2022] Open
Abstract
10.1601/nm.1335 Mlalz-1 (INSDC = ATZD00000000) is an aerobic, motile, Gram-negative, non-spore-forming rod that was isolated from an effective nitrogen-fixing nodule of Medicago laciniata (L.) Miller from a soil sample collected near the town of Guatiza on the island of Lanzarote, the Canary Islands, Spain. This strain nodulates and forms an effective symbiosis with the highly specific host M. laciniata. This rhizobial genome was sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) sequencing project. Here the features of 10.1601/nm.1335 Mlalz-1 are described, together with high-quality permanent draft genome sequence information and annotation. The 6,664,116 bp high-quality draft genome is arranged in 99 scaffolds of 100 contigs, containing 6314 protein-coding genes and 74 RNA-only encoding genes. Strain Mlalz-1 is closely related to 10.1601/nm.1335 10.1601/strainfinder?urlappend=%3Fid%3DIAM+12611 T, 10.1601/nm.1334 A 321T and 10.1601/nm.17831 10.1601/strainfinder?urlappend=%3Fid%3DORS+1407 T, based on 16S rRNA gene sequences. gANI values of ≥98.1% support the classification of strain Mlalz-1 as 10.1601/nm.1335. Nodulation of M. laciniata requires a specific nodC allele, and the nodC gene of strain Mlalz-1 shares ≥98% sequence identity with nodC of M. laciniata-nodulating 10.1601/nm.1328 strains, but ≤93% with nodC of 10.1601/nm.1328 strains that nodulate other Medicago species. Strain Mlalz-1 is unique among sequenced 10.1601/nm.1335 strains in possessing genes encoding components of a T2SS and in having two versions of the adaptive acid tolerance response lpiA-acvB operon. In 10.1601/nm.1334 strain 10.1601/strainfinder?urlappend=%3Fid%3DWSM+419, lpiA is essential for enhancing survival in lethal acid conditions. The second copy of the lpiA-acvB operon of strain Mlalz-1 has highest sequence identity (> 96%) with that of 10.1601/nm.1334 strains, which suggests genetic recombination between strain Mlalz-1 and 10.1601/nm.1334 and the horizontal gene transfer of lpiA-acvB.
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Affiliation(s)
| | - Peter van Berkum
- U.S. Department of Agriculture, Soybean Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, 10300 Baltimore Avenue, Bldg. 006, Beltsville, MD 20705 USA
| | - Milagros León-Barrios
- Departamento de Bioquímica, Microbiología, Biología Celular y Genética, Universidad de La Laguna, Tenerife, Spain
| | - Encarna Velázquez
- Departamento de Microbiología y Genetica and Instituto Hispanoluso de Investigaciones Agrarias (CIALE), Universidad de Salamanca, Salamanca, Spain
| | - Patrick Elia
- U.S. Department of Agriculture, Soybean Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, 10300 Baltimore Avenue, Bldg. 006, Beltsville, MD 20705 USA
| | - Rui Tian
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA Australia
| | - Julie Ardley
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA Australia
| | - Margaret Gollagher
- Curtin University Sustainability Policy Institute, Curtin University, Bentley, WA Australia
| | | | | | | | - Tanja Woyke
- DOE Joint Genome Institute, Walnut Creek, CA USA
| | - Amrita Pati
- Biological Data Management and Technology Center, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - Victor Markowitz
- Biological Data Management and Technology Center, Lawrence Berkeley National Laboratory, Berkeley, CA USA
| | - Mohamed N. Baeshen
- Department of Biology, Faculty of Science, University of Jeddah, Jeddah, Saudi Arabia
| | | | | | - Wayne Reeve
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA Australia
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Passaglia LMP. Bradyrhizobium elkanii nod regulon: insights through genomic analysis. Genet Mol Biol 2017; 40:703-716. [PMID: 28767122 PMCID: PMC5596368 DOI: 10.1590/1678-4685-gmb-2016-0228] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 02/16/2017] [Indexed: 12/26/2022] Open
Abstract
A successful symbiotic relationship between soybean [Glycinemax (L.) Merr.] and Bradyrhizobium species requires expression of the bacterial structural nod genes that encode for the synthesis of lipochitooligosaccharide nodulation signal molecules, known as Nod factors (NFs). Bradyrhizobium diazoefficiens USDA 110 possesses a wide nodulation gene repertoire that allows NF assembly and modification, with transcription of the nodYABCSUIJnolMNOnodZ operon depending upon specific activators, i.e., products of regulatory nod genes that are responsive to signaling molecules such as flavonoid compounds exuded by host plant roots. Central to this regulatory circuit of nod gene expression are NodD proteins, members of the LysR-type regulator family. In this study, publicly available Bradyrhizobium elkanii sequenced genomes were compared with the closely related B. diazoefficiens USDA 110 reference genome to determine the similarities between those genomes, especially with regards to the nod operon and nod regulon. Bioinformatics analyses revealed a correlation between functional mechanisms and key elements that play an essential role in the regulation of nod gene expression. These analyses also revealed new genomic features that had not been clearly explored before, some of which were unique for some B. elkanii genomes.
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Affiliation(s)
- Luciane M P Passaglia
- Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil
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12
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Geddes BA, Oresnik IJ. The Mechanism of Symbiotic Nitrogen Fixation. ADVANCES IN ENVIRONMENTAL MICROBIOLOGY 2016. [DOI: 10.1007/978-3-319-28068-4_4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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del Cerro P, Rolla-Santos AAP, Gomes DF, Marks BB, Pérez-Montaño F, Rodríguez-Carvajal MÁ, Nakatani AS, Gil-Serrano A, Megías M, Ollero FJ, Hungria M. Regulatory nodD1 and nodD2 genes of Rhizobium tropici strain CIAT 899 and their roles in the early stages of molecular signaling and host-legume nodulation. BMC Genomics 2015; 16:251. [PMID: 25880529 PMCID: PMC4393855 DOI: 10.1186/s12864-015-1458-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 03/09/2015] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Nodulation and symbiotic nitrogen fixation are mediated by several genes, both of the host legume and of the bacterium. The rhizobial regulatory nodD gene plays a critical role, orchestrating the transcription of the other nodulation genes. Rhizobium tropici strain CIAT 899 is an effective symbiont of several legumes-with an emphasis on common bean (Phaseolus vulgaris)-and is unusual in carrying multiple copies of nodD, the roles of which remain to be elucidated. RESULTS Phenotypes, Nod factors and gene expression of nodD1 and nodD2 mutants of CIAT 899 were compared with those of the wild type strain, both in the presence and in the absence of the nod-gene-inducing molecules apigenin and salt (NaCl). Differences between the wild type and mutants were observed in swimming motility and IAA (indole acetic acid) synthesis. In the presence of both apigenin and salt, large numbers of Nod factors were detected in CIAT 899, with fewer detected in the mutants. nodC expression was lower in both mutants; differences in nodD1 and nodD2 expression were observed between the wild type and the mutants, with variation according to the inducing molecule, and with a major role of apigenin with nodD1 and of salt with nodD2. In the nodD1 mutant, nodulation was markedly reduced in common bean and abolished in leucaena (Leucaena leucocephala) and siratro (Macroptilium atropurpureum), whereas a mutation in nodD2 reduced nodulation in common bean, but not in the other two legumes. CONCLUSION Our proposed model considers that full nodulation of common bean by R. tropici requires both nodD1 and nodD2, whereas, in other legume species that might represent the original host, nodD1 plays the major role. In general, nodD2 is an activator of nod-gene transcription, but, in specific conditions, it can slightly repress nodD1. nodD1 and nodD2 play other roles beyond nodulation, such as swimming motility and IAA synthesis.
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Affiliation(s)
- Pablo del Cerro
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6 Apdo Postal 41012, Sevilla, Spain.
| | | | | | | | - Francisco Pérez-Montaño
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6 Apdo Postal 41012, Sevilla, Spain.
| | | | | | - Antonio Gil-Serrano
- Departamento de Química Orgánica, Facultad de Química, Universidad de Sevilla, Apdo Postal 553, 41071, Sevilla, Spain.
| | - Manuel Megías
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6 Apdo Postal 41012, Sevilla, Spain.
| | - Francisco Javier Ollero
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6 Apdo Postal 41012, Sevilla, Spain.
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Suzaki T, Yoro E, Kawaguchi M. Leguminous plants: inventors of root nodules to accommodate symbiotic bacteria. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 316:111-58. [PMID: 25805123 DOI: 10.1016/bs.ircmb.2015.01.004] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Legumes and a few other plant species can establish a symbiotic relationship with nitrogen-fixing rhizobia, which enables them to survive in a nitrogen-deficient environment. During the course of nodulation, infection with rhizobia induces the dedifferentiation of host cells to form primordia of a symbiotic organ, the nodule, which prepares plants to accommodate rhizobia in host cells. While these nodulation processes are known to be genetically controlled by both plants and rhizobia, recent advances in studies on two model legumes, Lotus japonicus and Medicago truncatula, have provided great insight into the underlying plant-side molecular mechanism. In this chapter, we review such knowledge, with particular emphasis on two key processes of nodulation, nodule development and rhizobial invasion.
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Affiliation(s)
- Takuya Suzaki
- National Institute for Basic Biology, Okazaki, Japan; School of Life Science, Graduate University for Advanced Studies, Okazaki, Japan
| | - Emiko Yoro
- National Institute for Basic Biology, Okazaki, Japan; School of Life Science, Graduate University for Advanced Studies, Okazaki, Japan
| | - Masayoshi Kawaguchi
- National Institute for Basic Biology, Okazaki, Japan; School of Life Science, Graduate University for Advanced Studies, Okazaki, Japan
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15
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Morieri G, Martinez EA, Jarynowski A, Driguez H, Morris R, Oldroyd GED, Downie JA. Host-specific Nod-factors associated with Medicago truncatula nodule infection differentially induce calcium influx and calcium spiking in root hairs. THE NEW PHYTOLOGIST 2013; 200:656-662. [PMID: 24015832 PMCID: PMC3908372 DOI: 10.1111/nph.12475] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 08/01/2013] [Indexed: 05/21/2023]
Abstract
Rhizobial nodulation (Nod) factors activate both nodule morphogenesis and infection thread development during legume nodulation. Nod factors induce two different calcium responses: intra-nuclear calcium oscillations and a calcium influx at the root hair tip. Calcium oscillations activate nodule development; we wanted to test if the calcium influx is associated with infection. Sinorhizobium meliloti nodL and nodF mutations additively reduce infection of Medicago truncatula. Nod-factors made by the nodL mutant lack an acetyl group; mutation of nodF causes the nitrogen (N)-linked C16:2 acyl chain to be replaced by C18:1. We tested whether these Nod-factors differentially induced calcium influx and calcium spiking. The absence of the NodL-determined acetyl group greatly reduced the induction of calcium influx without affecting calcium spiking. The calcium influx was even further reduced if the N-linked C16:2 acyl group was replaced by C18:1. These additive effects on calcium influx correlate with the additive effects of mutations in nodF and nodL on legume infection. Infection thread development is inhibited by ethylene, which also inhibited Nod-factor-induced calcium influx. We conclude that Nod-factor perception differentially activates the two developmental pathways required for nodulation and that activation of the pathway involving the calcium influx is important for efficient infection.
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Affiliation(s)
- Giulia Morieri
- John Innes CentreNorwich Research Park, Colney, Norwich, NR4 7UH, UK
| | - Eduardo A Martinez
- Centre de Recherches sur les Macromolécules Végétales, CNRSB.P. 53, F-38041, Grenoble CEDEX 9, France
| | | | - Hugues Driguez
- Centre de Recherches sur les Macromolécules Végétales, CNRSB.P. 53, F-38041, Grenoble CEDEX 9, France
| | - Richard Morris
- John Innes CentreNorwich Research Park, Colney, Norwich, NR4 7UH, UK
| | - Giles E D Oldroyd
- John Innes CentreNorwich Research Park, Colney, Norwich, NR4 7UH, UK
| | - J Allan Downie
- John Innes CentreNorwich Research Park, Colney, Norwich, NR4 7UH, UK
- Author for correspondence: J. Allan DownieTel: +44 1603 450207
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Isolation and characterization of mutant Sinorhizobium meliloti NodD1 proteins with altered responses to luteolin. J Bacteriol 2013; 195:3714-23. [PMID: 23772067 DOI: 10.1128/jb.00309-13] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
NodD1, a member of the NodD family of LysR-type transcriptional regulators (LTTRs), mediates nodulation (nod) gene expression in the soil bacterium Sinorhizobium meliloti in response to the plant-secreted flavonoid luteolin. We used genetic screens and targeted approaches to identify NodD1 residues that show altered responses to luteolin during the activation of nod gene transcription. Here we report four types of NodD1 mutants. Type I (NodD1 L69F, S104L, D134N, and M193I mutants) displays reduced or no activation of nod gene expression. Type II (NodD1 K205N) is constitutively active but repressed by luteolin. Type III (NodD1 L280F) demonstrates enhanced activity with luteolin compared to that of wild-type NodD1. Type IV (NodD1 D284N) shows moderate constitutive activity yet can still be induced by luteolin. In the absence of luteolin, many mutants display a low binding affinity for nod gene promoter DNA in vitro. Several mutants also show, as does wild-type NodD1, increased affinity for nod gene promoters with added luteolin. All of the NodD1 mutant proteins can homodimerize and heterodimerize with wild-type NodD1. Based on these data and the crystal structures of several LTTRs, we present a structural model of wild-type NodD1, identifying residues important for inducer binding, protein multimerization, and interaction with RNA polymerase at nod gene promoters.
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17
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Somers E, Vanderleyden J, Srinivasan M. Rhizosphere Bacterial Signalling: A Love Parade Beneath Our Feet. Crit Rev Microbiol 2008; 30:205-40. [PMID: 15646398 DOI: 10.1080/10408410490468786] [Citation(s) in RCA: 165] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Plant roots support the growth and activities of a wide variety of microorganisms that may have a profound effect on the growth and/or health of plants. Among these microorganisms, a high diversity of bacteria have been identified and categorized as deleterious, beneficial, or neutral with respect to the plant. The beneficial bacteria, termed plant growth-promoting rhizobacteria (PGPR), are widely studied by microbiologists and agronomists because of their potential in plant production. Azospirillum, a genus of versatile PGPR, is able to enhance the plant growth and yield of a wide range of economically important crops in different soils and climatic regions. Plant beneficial effects of Azospirillum have mainly been attributed to the production of phytohormones, nitrate reduction, and nitrogen fixation, which have been subject of extensive research throughout the years. These elaborate studies made Azospirillum one of the best-characterized genera of PGPR. However, the genetic and molecular determinants involved in the initial interaction between Azospirillum and plant roots are not yet fully understood. This review will mainly highlight the current knowledge on Azospirillum plant root interactions, in the context of preceding and ongoing research on the association between plants and plant growth-promoting rhizobacteria.
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Affiliation(s)
- E Somers
- Centre of Microbial and Plant Genetics, K U Leuven, Heverlee, Belgium.
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18
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19
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Zhang J, Subramanian S, Zhang Y, Yu O. Flavone synthases from Medicago truncatula are flavanone-2-hydroxylases and are important for nodulation. PLANT PHYSIOLOGY 2007; 144:741-51. [PMID: 17434990 PMCID: PMC1914186 DOI: 10.1104/pp.106.095018] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Flavones are important copigments found in the flowers of many higher plants and play a variety of roles in plant adaptation to stress. In Medicago species, flavones also act as signal molecules during symbiotic interaction with the diazotropic bacterium Sinorhizobium meliloti. They are the most potent nod gene inducers found in root exudates. However, flavone synthase II (FNS II), the key enzyme responsible for flavone biosynthesis, has not been characterized in Medicago species. We cloned two FNS II genes from Medicago truncatula using known FNS II sequences from other species and named them MtFNSII-1 and MtFNSII-2. Functional assays in yeast (Saccharomyces cerevisiae) suggested that the catalytic mechanisms of both cytochrome P450 monooxygenases were similar to the other known legume FNS II from licorice (Glycyrrhiza echinata). MtFNSII converted flavanones to 2-hydroxyflavanones instead of flavones whereas FNS II from the nonlegume Gerbera hybrida, converted flavanones to flavones directly. The two MtFNSII genes had distinct tissue-specific expression patterns. MtFNSII-1 was highly expressed in roots and seeds whereas MtFNSII-2 was highly expressed in flowers and siliques. In addition, MtFNSII-2 was inducible by S. meliloti and methyl jasmonate treatment, whereas MtFNSII-1 was not. Histochemical staining of transgenic hairy roots carrying the promoter-reporter constructs indicated that the MtFNSII-2 induction was tissue specific, mostly localized to vascular tissues and root hairs. RNA interference-mediated suppression of MtFNSII genes resulted in flavone depleted roots and led to significantly reduced nodulation when inoculated with S. meliloti. Our results provide genetic evidence supporting that flavones are important for nodulation in M. truncatula.
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Affiliation(s)
- Juan Zhang
- Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA
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20
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Mabood F, Souleimanov A, Khan W, Smith DL. Jasmonates induce Nod factor production by Bradyrhizobium japonicum. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2006; 44:759-65. [PMID: 17107814 DOI: 10.1016/j.plaphy.2006.10.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 10/10/2006] [Indexed: 05/03/2023]
Abstract
Jasmonates are signaling molecules involved in induced systemic resistance, wounding and stress responses of plants. We have previously demonstrated that jasmonates can induce nod genes of Bradyrhizobium japonicum when measured by beta-galactosidase activity. In order to test whether jasmonates can effectively induce the production and secretion of Nod factors (lipo-chitooligosaccharides, LCOs) from B. japonicum, we induced two B. japonicum strains, 532C and USDA3, with jasmonic acid (JA), methyl jasmonate (MeJA) and genistein (Ge). As genistein is well characterized as an inducer of nod genes it was used a positive control. The high-performance liquid chromatography (HPLC) profile of LCOs isolated following treatment with jasmonates or genistein showed that both JA and MeJA effectively induced nod genes and caused production of LCOs from bacterial cultures. JA and MeJA are more efficacious inducers of LCO production than genistein. Genistein plus JA or MeJA resulted in greater LCO production than either alone. A soybean root hair deformation assay showed that jasmonate induced LCOs were as effective as those induced by genistein. This is the first report that jasmonates induce Nod factor production by B. japonicum. This report establishes the role of jasmonates as a new class of signaling molecules in the Bradyrhizobium-soybean symbiosis.
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Affiliation(s)
- F Mabood
- Plant Science Department, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Sainte-Anne-de-Bellevue, Que., Canada.
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21
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Peck MC, Fisher RF, Long SR. Diverse flavonoids stimulate NodD1 binding to nod gene promoters in Sinorhizobium meliloti. J Bacteriol 2006; 188:5417-27. [PMID: 16855231 PMCID: PMC1540014 DOI: 10.1128/jb.00376-06] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
NodD1 is a member of the NodD family of LysR-type transcriptional regulators that mediates the expression of nodulation (nod) genes in the soil bacterium Sinorhizobium meliloti. Each species of rhizobia establishes a symbiosis with a limited set of leguminous plants. This host specificity results in part from a NodD-dependent upregulation of nod genes in response to a cocktail of flavonoids in the host plant's root exudates. To demonstrate that NodD is a key determinant of host specificity, we expressed nodD genes from different species of rhizobia in a strain of S. meliloti lacking endogenous NodD activity. We observed that nod gene expression was initiated in response to distinct sets of flavonoid inducers depending on the source of NodD. To better understand the effects of flavonoids on NodD, we assayed the DNA binding activity of S. meliloti NodD1 treated with the flavonoid inducer luteolin. In the presence of luteolin, NodD1 exhibited increased binding to nod gene promoters compared to binding in the absence of luteolin. Surprisingly, although they do not stimulate nod gene expression in S. meliloti, the flavonoids naringenin, eriodictyol, and daidzein also stimulated an increase in the DNA binding affinity of NodD1 to nod gene promoters. In vivo competition assays demonstrate that noninducing flavonoids act as competitive inhibitors of luteolin, suggesting that both inducing and noninducing flavonoids are able to directly bind to NodD1 and mediate conformational changes at nod gene promoters but that only luteolin is capable of promoting the downstream changes necessary for nod gene induction.
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Affiliation(s)
- Melicent C Peck
- Department of Biological Sciences, Gilbert Lab, 371 Serra Mall, Stanford University, Stanford, CA 94305, USA
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22
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Capela D, Carrere S, Batut J. Transcriptome-based identification of the Sinorhizobium meliloti NodD1 regulon. Appl Environ Microbiol 2005; 71:4910-3. [PMID: 16085895 PMCID: PMC1183327 DOI: 10.1128/aem.71.8.4910-4913.2005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The NodD1 regulon of Sinorhizobium meliloti was determined through the analysis of the S. meliloti transcriptome in response to the plant flavone luteolin and the overexpression of nodD1. Nine new genes regulated by both NodD1 and luteolin were identified, demonstrating that NodD1 controls few functions behind nodulation in S. meliloti.
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Affiliation(s)
- Delphine Capela
- Laboratoire des Interactions Plantes-Microorganismes, INRA-CNRS, BP52627, 31326 Castanet-Tolosan Cedex, France.
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23
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Abstract
sigma54 is unique among the bacterial sigma factors. Besides not being related in sequence with the rest of such factors, its mechanism of transcription initiation is completely different and requires the participation of a transcription activator. In addition, whereas the rest of the alternative sigma factors use to be involved in transcription of somehow related biological functions, this is not the case for sigma54 and many different and unrelated genes have been shown to be transcribed from sigma54-dependent promoters, ranging from flagellation, to utilization of several different carbon and nitrogen sources, or alginate biosynthesis. These genes have been characterized in many different bacterial species and, only until recently with the arrival of complete genome sequences, we have been able to look at the sigma54 functional role from a genomic perspective. Aided by computational methods, the sigma54 regulon has been studied both in Escherichia coli, Salmonella typhimurium and several species of the Rhizobiaceae. Here we present the analysis of the sigma54 regulon (sigmulon) in the complete genome of Pseudomonas putida KT2440. We have developed an improved method for the prediction of sigma54-dependent promoters which combines the scores of sigma54-RNAP target sequences and those of activator binding sites. In combination with other evidence obtained from the chromosomal context and the similarity with closely related bacteria, we have been able to predict more than 80% of the sigma54-dependent promoters of P. putida with high confidence. Our analysis has revealed new functions for sigma54 and, by means of comparative analysis with the previous studies, we have drawn a potential mechanism for the evolution of this regulatory system.
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Affiliation(s)
- Ildefonso Cases
- Centro Nacional de Biotecnología, CSIC Campus de Cantoblanco, 28049 Madrid, Spain
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Amor BB, Shaw SL, Oldroyd GED, Maillet F, Penmetsa RV, Cook D, Long SR, Dénarié J, Gough C. The NFP locus of Medicago truncatula controls an early step of Nod factor signal transduction upstream of a rapid calcium flux and root hair deformation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 34:495-506. [PMID: 12753588 DOI: 10.1046/j.1365-313x.2003.01743.x] [Citation(s) in RCA: 225] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Establishment of the Rhizobium-legume symbiosis depends on a molecular dialogue, in which rhizobial nodulation (Nod) factors act as symbiotic signals, playing a key role in the control of specificity of infection and nodule formation. Using nodulation-defective (Nod-) mutants of Medicago truncatula to study the mechanisms controlling Nod factor perception and signalling, we have previously identified five genes that control components of a Nod factor-activated signal transduction pathway. Characterisation of a new M. truncatula Nod- mutant led to the identification of the Nod Factor Perception (NFP) locus. The nfp mutant has a novel phenotype among Nod- mutants of M. truncatula, as it does not respond to Nod factors by any of the responses tested. The nfp mutant thus shows no rapid calcium flux, the earliest detectable Nod factor response of wild-type plants, and no root hair deformation. The nfp mutant is also deficient in Nod factor-induced calcium spiking and early nodulin gene expression. While certain genes controlling Nod factor signal transduction also control the establishment of an arbuscular mycorrhizal symbiosis, the nfp mutant shows a wild-type mycorrhizal phenotype. These data indicate that the NFP locus controls an early step of Nod factor signal transduction, upstream of previously identified genes and specific to nodulation.
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Affiliation(s)
- Besma Ben Amor
- Laboratoire des Interactions Plantes-Microorganismes, INRA-CNRS, BP 27, 31326 Castanet-Tolosan, France
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25
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Suominen L, Luukkainen R, Roos C, Lindström K. Activation of the nodA promoter by the nodD genes of Rhizobium galegae induced by synthetic flavonoids or Galega orientalis root exudate. FEMS Microbiol Lett 2003; 219:225-32. [PMID: 12620625 DOI: 10.1016/s0378-1097(02)01206-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Rhizobial nodD genes produce transcriptional regulators that, together with appropriate inducer compounds, activate the other symbiotic nodulation (nod) genes and initiate the nodule formation process. Two nodD homologues, nodD1 and nodD2, are present in the Rhizobium galegae strain HAMBI 1174. In this work we analysed their ability to induce the nodA promoter with synthetic inducers known to activate nod genes in other rhizobia. According to phylogenetic analysis, the inducer-specific carboxy-terminal part of the R. galegae nodD protein sequence groups together with those of Rhizobium leguminosarum and Sinorhizobium meliloti. However, the respective inducer compounds for their NodD proteins are not highly effective with R. galegae nodD products. The best inducer discovered with R. galegae nodD1 was the root exudate of the host plant of R. galegae, Galega orientalis. HPLC analyses revealed the presence of many divergent flavonoid compounds in the G. orientalis root exudate. The most effective HPLC fractions induced R. galegae nodD1 up to the level obtained by intact G. orientalis root exudate while apigenin and luteolin, which were also present in the root exudate, were only moderate inducers. A UV-Vis diode array spectrum of the most active peak indicated that the main inducer present in the G. orientalis root exudate is an unidentified chalcone-type compound. In the Galega-R. galegae interaction the first recognition between the NodD protein and the flavonoid inducer secreted from the roots of Galega is specific for these organisms, and thus partly responsible of the strict host specificity of this symbiosis.
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Affiliation(s)
- Leena Suominen
- Department of Applied Chemistry and Microbiology, Biocenter 1, University of Helsinki, 00014, Helsinki, Finland.
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Loh J, Stacey G. Nodulation gene regulation in Bradyrhizobium japonicum: a unique integration of global regulatory circuits. Appl Environ Microbiol 2003; 69:10-7. [PMID: 12513971 PMCID: PMC152446 DOI: 10.1128/aem.69.1.10-17.2003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- John Loh
- Department of Plant Microbiology and Pathology, University of Missouri, Columbia, Missouri 65211, USA
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Wais RJ, Wells DH, Long SR. Analysis of differences between Sinorhizobium meliloti 1021 and 2011 strains using the host calcium spiking response. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2002; 15:1245-1252. [PMID: 12481997 DOI: 10.1094/mpmi.2002.15.12.1245] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In the Rhizobium-legume symbiosis, compatible partners recognize each other through an exchange of signals. Plant inducers act together with bacterial transcriptional activators, the NodD proteins, to regulate the expression of bacterial biosynthetic nodulation (nod) genes. These genes direct the synthesis of a lipochito-oligosaccharide signal called Nod factor (NF). NFs elicit an early host response, root hair calcium spiking, that is initiated in root hair cells within 15 min of NF or live Rhizobium inoculation. We used calcium spiking as an assay to compare two closely related strains of Sinorhizobium meliloti, Rm1021 and Rm2011, derived from the same field isolate. We found that the two strains show a kinetic difference in the calcium spiking assay: Rm1021 elicits calcium spiking in host root hairs as rapidly as purified NF, whereas Rm2011 shows a significant delay. This difference can be overcome by raising expression levels of either the NodD transcriptional activators or GroEL, a molecular chaperone that affects expression of the biosynthetic nod genes. We further demonstrate that the delay in triggering calcium spiking exhibited by Rm2011 is correlated with a reduced amount of nod gene expression compared with Rm1021. Therefore, calcium spiking is a useful tool in detecting subtle differences in bacterial gene expression that affect the early stages of the Rhizobium-legume symbiosis.
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Affiliation(s)
- Rebecca J Wais
- Department of Biological Sciences, Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305-5020, USA
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28
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Abstract
Sinorhizobium meliloti and host legumes enter into a nitrogen-fixing, symbiotic relationship triggered by an exchange of signals between bacteria and plant. S. meliloti produces Nod factor, which elicits the formation of nodules on plant roots, and succinoglycan, an exopolysaccharide that allows for bacterial invasion and colonization of the host. The biosynthesis of these molecules is well defined, but the specific regulation of these compounds is not completely understood. Bacteria control complex regulatory networks by the production of ppGpp, the effector molecule of the stringent response, which induces physiological change in response to adverse growth conditions and can also control bacterial development and virulence. Through detailed analysis of an S. meliloti mutant incapable of producing ppGpp, we show that the stringent response is required for nodule formation and regulates the production of succinoglycan. Although it remains unknown whether these phenotypes are connected, we have isolated suppressor strains that restore both defects and potentially identify key downstream regulatory genes. These results indicate that the S. meliloti stringent response has roles in both succinoglycan production and nodule formation and, more importantly, that control of bacterial physiology in response to the plant and surrounding environment is critical to the establishment of a successful symbiosis.
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Affiliation(s)
- Derek H Wells
- Department of Biological Sciences, 371 Serra Mall, Stanford University, Stanford, CA 94305-5020, USA
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Suominen L, Roos C, Lortet G, Paulin L, Lindström K. Identification and Structure of the Rhizobium galegae Common Nodulation Genes: Evidence for Horizontal Gene Transfer. Mol Biol Evol 2001; 18:907-16. [PMID: 11371578 DOI: 10.1093/oxfordjournals.molbev.a003891] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Rhizobia are soil bacteria able to fix atmospheric nitrogen in symbiosis with leguminous plants. In response to a signal cascade coded by genes of both symbiotic partners, a specific plant organ, the nodule, is formed. Rhizobial nodulation (nod) genes trigger nodule formation through the synthesis of Nod factors, a family of chitolipooligosaccharides that are specifically recognized by the host plant at the first stages of the nodulation process. Here, we present the organization and sequence of the common nod genes from Rhizobium galegae, a symbiotic member of the RHIZOBIACEAE: This species has an intriguing phylogenetic position, being symbiotic among pathogenic agrobacteria, which induce tumors instead of nodules in plant shoots or roots. This apparent incongruence raises special interest in the origin of the symbiotic apparatus of R. galegae. Our analysis of DNA sequence data indicated that the organization of the common nod gene region of R. galegae was similar to that of Sinorhizobium meliloti and Rhizobium leguminosarum, with nodIJ downstream of nodABC and the regulatory nodD gene closely linked to the common nod operon. Moreover, phylogenetic analyses of the nod gene sequences showed a close relationship especially between the common nodA sequences of R. galegae, S. meliloti, and R. leguminosarum biovars viciae and trifolii. This relationship in structure and sequence contrasts with the phylogeny based on 16S rRNA, which groups R. galegae close to agrobacteria and separate from most other rhizobia. The topology of the nodA tree was similar to that of the corresponding host plant tree. Taken together, these observations indicate that lateral nod gene transfer occurred from fast-growing rhizobia toward agrobacteria, after which the symbiotic apparatus evolved under host plant constraint.
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Affiliation(s)
- L Suominen
- Department of Applied Chemistry and Microbiology, Institute of Biotechnology, University of Helsinki, Biocenter 1, FIN-00014 Helsinki, Finland.
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Catoira R, Timmers AC, Maillet F, Galera C, Penmetsa RV, Cook D, Dénarié J, Gough C. The HCL gene of Medicago truncatula controls Rhizobium-induced root hair curling. Development 2001; 128:1507-18. [PMID: 11290290 DOI: 10.1242/dev.128.9.1507] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The symbiotic infection of the model legume Medicago truncatula by Sinorhizobium meliloti involves marked root hair curling, a stage where entrapment of the microsymbiont occurs in a chamber from which infection thread formation is initiated within the root hair. We have genetically dissected these early symbiotic interactions using both plant and rhizobial mutants and have identified a M. truncatula gene, HCL, which controls root hair curling. S. meliloti Nod factors, which are required for the infection process, induced wild-type epidermal nodulin gene expression and root hair deformation in hcl mutants, while Nod factor induction of cortical cell division foci was reduced compared to wild-type plants. Studies of the position of nuclei and of the microtubule cytoskeleton network of hcl mutants revealed that root hair, as well as cortical cells, were activated in response to S. meliloti. However, the asymmetric microtubule network that is typical of curled root hairs, did not form in the mutants, and activated cortical cells did not become polarised and did not exhibit the microtubular cytoplasmic bridges characteristic of the pre-infection threads induced by rhizobia in M. truncatula. These data suggest that hcl mutations alter the formation of signalling centres that normally provide positional information for the reorganisation of the microtubular cytoskeleton in epidermal and cortical cells.
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Affiliation(s)
- R Catoira
- Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, CNRS-INRA UMR215, BP27, France
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31
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Catoira R, Galera C, de Billy F, Penmetsa RV, Journet EP, Maillet F, Rosenberg C, Cook D, Gough C, Dénarié J. Four genes of Medicago truncatula controlling components of a nod factor transduction pathway. THE PLANT CELL 2000; 12:1647-66. [PMID: 11006338 PMCID: PMC149076 DOI: 10.1105/tpc.12.9.1647] [Citation(s) in RCA: 338] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2000] [Accepted: 06/23/2000] [Indexed: 05/17/2023]
Abstract
Rhizobium nodulation (Nod) factors are lipo-chitooligosaccharides that act as symbiotic signals, eliciting several key developmental responses in the roots of legume hosts. Using nodulation-defective mutants of Medicago truncatula, we have started to dissect the genetic control of Nod factor transduction. Mutants in four genes (DMI1, DMI2, DMI3, and NSP) were pleiotropically affected in Nod factor responses, indicating that these genes are required for a Nod factor-activated signal transduction pathway that leads to symbiotic responses such as root hair deformations, expressions of nodulin genes, and cortical cell divisions. Mutant analysis also provides evidence that Nod factors have a dual effect on the growth of root hair: inhibition of endogenous (plant) tip growth, and elicitation of a novel tip growth dependent on (bacterial) Nod factors. dmi1, dmi2, and dmi3 mutants are also unable to establish a symbiotic association with endomycorrhizal fungi, indicating that there are at least three common steps to nodulation and endomycorrhization in M. truncatula and providing further evidence for a common signaling pathway between nodulation and mycorrhization.
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Affiliation(s)
- R Catoira
- Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, Centre National de la Recherche Scientifique-Institut National de la Recherche Agronomique (INRA-CNRS) UMR215, BP27, 31326 Castanet-Tolosan Cedex, France
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32
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Zhang XX, Turner SL, Guo XW, Yang HJ, Debellé F, Yang GP, Dénarié J, Young JP, Li FD. The common nodulation genes of Astragalus sinicus rhizobia are conserved despite chromosomal diversity. Appl Environ Microbiol 2000; 66:2988-95. [PMID: 10877796 PMCID: PMC92101 DOI: 10.1128/aem.66.7.2988-2995.2000] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nodulation genes of Mesorhizobium sp. (Astragalus sinicus) strain 7653R were cloned by functional complementation of Sinorhizobium meliloti nod mutants. The common nod genes, nodD, nodA, and nodBC, were identified by heterologous hybridization and sequence analysis. The nodA gene was found to be separated from nodBC by approximately 22 kb and was divergently transcribed. The 2. 0-kb nodDBC region was amplified by PCR from 24 rhizobial strains nodulating A. sinicus, which represented different chromosomal genotypes and geographic origins. No polymorphism was found in the size of PCR products, suggesting that the separation of nodA from nodBC is a common feature of A. sinicus rhizobia. Sequence analysis of the PCR-amplified nodA gene indicated that seven strains representing different 16S and 23S ribosomal DNA genotypes had identical nodA sequences. These data indicate that, whereas microsymbionts of A. sinicus exhibit chromosomal diversity, their nodulation genes are conserved, supporting the hypothesis of horizontal transfer of nod genes among diverse recipient bacteria.
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Affiliation(s)
- X X Zhang
- Department of Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
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33
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Abstract
Eukaryotes often form symbioses with microorganisms. Among these, associations between plants and nitrogen-fixing bacteria are responsible for the nitrogen input into various ecological niches. Plants of many different families have evolved the capacity to develop root or stem nodules with diverse genera of soil bacteria. Of these, symbioses between legumes and rhizobia (Azorhizobium, Bradyrhizobium, Mesorhizobium, and Rhizobium) are the most important from an agricultural perspective. Nitrogen-fixing nodules arise when symbiotic rhizobia penetrate their hosts in a strictly controlled and coordinated manner. Molecular codes are exchanged between the symbionts in the rhizosphere to select compatible rhizobia from pathogens. Entry into the plant is restricted to bacteria that have the "keys" to a succession of legume "doors". Some symbionts intimately associate with many different partners (and are thus promiscuous), while others are more selective and have a narrow host range. For historical reasons, narrow host range has been more intensively investigated than promiscuity. In our view, this has given a false impression of specificity in legume-Rhizobium associations. Rather, we suggest that restricted host ranges are limited to specific niches and represent specialization of widespread and more ancestral promiscuous symbioses. Here we analyze the molecular mechanisms governing symbiotic promiscuity in rhizobia and show that it is controlled by a number of molecular keys.
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Affiliation(s)
- X Perret
- Laboratoire de Biologie Moléculaire des Plantes Supérieures, Université de Genève, 1292 Chambésy/Geneva, Switzerland
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Yang GP, Debellé F, Savagnac A, Ferro M, Schiltz O, Maillet F, Promé D, Treilhou M, Vialas C, Lindstrom K, Dénarié J, Promé JC. Structure of the Mesorhizobium huakuii and Rhizobium galegae Nod factors: a cluster of phylogenetically related legumes are nodulated by rhizobia producing Nod factors with alpha,beta-unsaturated N-acyl substitutions. Mol Microbiol 1999; 34:227-37. [PMID: 10564467 DOI: 10.1046/j.1365-2958.1999.01582.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Rhizobia are symbiotic bacteria that synthesize lipochitooligosaccharide Nod factors (NFs), which act as signal molecules in the nodulation of specific legume hosts. Based on the structure of their N-acyl chain, NFs can be classified into two categories: (i) those that are acylated with fatty acids from the general lipid metabolism; and (ii) those (= alphaU-NFs) that are acylated by specific alpha,beta-unsaturated fatty acids (containing carbonyl-conjugated unsaturation(s)). Previous work has described how rhizobia that nodulate legumes of the Trifolieae and Vicieae tribes produce alphaU-NFs. Here, we have studied the structure of NFs from two rhizobial species that nodulate important genera of the Galegeae tribe, related to Trifolieae and Vicieae. Three strains of Mesorhizobium huakuii, symbionts of Astragalus sinicus, produced as major NFs, pentameric lipochitooligosaccharides O-sulphated and partially N-glycolylated at the reducing end and N-acylated, at the non-reducing end, by a C18:4 fatty acid. Two strains of Rhizobium galegae, symbionts of Galega sp., produced as major NFs, tetrameric O-carbamoylated NFs that could be O-acetylated on the glucosamine residue next to the non-reducing terminal glucosamine and were N-acylated by C18 and C20 alpha,beta-unsaturated fatty acids. These results suggest that legumes nodulated by rhizobia synthesizing alphaU-NFs constitute a phylogenetic cluster in the Galegoid phylum.
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Affiliation(s)
- G P Yang
- Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, INRA-CNRS, BP27, 31326 Castanet-Tolosan Cedex, France
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35
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Suominen L, Paulin L, Saano A, Saren AM, Tas E, Lindström K. Identification of nodulation promoter (nod-box) regions of Rhizobium galegae. FEMS Microbiol Lett 1999; 177:217-23. [PMID: 10474187 DOI: 10.1111/j.1574-6968.1999.tb13735.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A hybridisation analysis of a genomic clone library of Rhizobium galegae HAMBI 1174 located four EcoRI fragments homologous to the nod-box promoter sequence of Sinorhizobium meliloti in two separate gene regions. Two of the five nod-boxes detected in the R. galegae genome were carried on a single cosmid clone, pRg30, upstream from the nodABCIJ and nodF genes, whereas the other three nod-boxes were carried on a different cosmid clone, pRg10. Hybridisations with various nod gene probes from S. meliloti and Rhizobium leguminosarum species detected a nodD homolog in pRg10. The sequence data obtained from regions adjacent to each nod-box in pRg10 confirmed the presence of a second nodD in the R. galegae genome and, in addition, revealed the presence of nodN, nodU, dctA nifH and nifQ-like genes in pRg10. Thus, by using a promoter-specific nod-box probe we could identify a new region carrying genes involved in nitrogen fixation and host specificity functions.
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Affiliation(s)
- L Suominen
- Department of Applied Chemistry and Microbiology, Helsinki University, Finland.
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36
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Binding of activator SyrM to the site ofnodD3 P1 region ofRhizobium meliloti. ACTA ACUST UNITED AC 1998; 41:157-62. [DOI: 10.1007/bf02882721] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/1997] [Indexed: 11/26/2022]
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37
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Fellay R, Hanin M, Montorzi G, Frey J, Freiberg C, Golinowski W, Staehelin C, Broughton WJ, Jabbouri S. nodD2 of Rhizobium sp. NGR234 is involved in the repression of the nodABC operon. Mol Microbiol 1998; 27:1039-50. [PMID: 9535093 DOI: 10.1046/j.1365-2958.1998.00761.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Transcriptional regulators of the lysR family largely control the expression of bacterial symbiotic genes. Rhizobium sp. NGR234 contains at least four members of this family: two resemble nodD, while two others are more closely related to syrM. Part of the extremely broad host range of NGR234 can be attributed to nodD1, although the second gene shares a high degree of DNA sequence homology with nodD2 of R. fredii USDA191. A nodD2 mutant of NGR234 was constructed by insertional mutagenesis. This mutant (NGR omega nodD2) was deficient in nitrogen fixation on Vigna unguiculata and induced pseudonodules on Tephrosia vogelii. Several other host plants were tested, but no correlation could be drawn between the phenotype and nodule morphology. Moreover, nodD2 has a negative effect on the production of Nod factors: mutation of this gene results in a fivefold increase in Nod factor production. Surprisingly, while the structure of Nod factors from free-living cultures of NGR omega nodD2 remained unchanged, those from V. unguiculata nodules induced by the same strain are non-fucosylated and have a lower degree of oligomerization. In other words, developmental regulation of Nod factor production is also abolished in this mutant. Competitive RNA hybridizations, gene fusions and mobility shift assays confirmed that nodD2 downregulates expression of the nodABC operon.
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Affiliation(s)
- R Fellay
- LBMPS, Université de Genève, Chambésy/Genève, Switzerland
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38
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Lorquin J, Lortet G, Ferro M, Mear N, Promé JC, Boivin C. Sinorhizobium teranga bv. acaciae ORS1073 and Rhizobium sp. strain ORS1001, two distantly related Acacia-nodulating strains, produce similar Nod factors that are O carbamoylated, N methylated, and mainly sulfated. J Bacteriol 1997; 179:3079-83. [PMID: 9139935 PMCID: PMC179081 DOI: 10.1128/jb.179.9.3079-3083.1997] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We have determined the structures of Nod factors produced by strains representative of Sinorhizobium teranga bv. acaciae and the so-called cluster U from the Rhizobium loti branch, two genetically different symbionts of particular Acacia species. Compounds from both strains were found to be similar, i.e., mainly sulfated, O carbamoylated, and N methylated, indicating a close relationship between host specificity and Nod factor structure, regardless of the taxonomy of the bacterial symbiont.
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Affiliation(s)
- J Lorquin
- Laboratoire de Microbiologie, ORSTOM, Institut Francais de Recherche Scientifique pour le Développement en Coopération, Dakar, Sénégal.
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39
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Arcondéguy T, Huez I, Tillard P, Gangneux C, de Billy F, Gojon A, Truchet G, Kahn D. The Rhizobium meliloti PII protein, which controls bacterial nitrogen metabolism, affects alfalfa nodule development. Genes Dev 1997; 11:1194-206. [PMID: 9159400 DOI: 10.1101/gad.11.9.1194] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Symbiotic nitrogen fixation involves the development of specialized organs called nodules within which plant photosynthates are exchanged for combined nitrogen of bacterial origin. To determine the importance of bacterial nitrogen metabolism in symbiosis, we have characterized a key regulator of this metabolism in Rhizobium meliloti, the uridylylatable P(II) protein encoded by glnB. We have constructed both a glnB null mutant and a point mutant making nonuridylylatable P(II). In free-living conditions, P(II) is required for expression of the ntrC-dependent gene glnII and for adenylylation of glutamine synthetase I. P(II) is also required for efficient infection of alfalfa but not for expression of nitrogenase. However alfalfa plants inoculated with either glnB mutant are nitrogen-starved in the absence of added combined nitrogen. We hypothesize that P(II) controls expression or activity of a bacteroid ammonium transporter required for a functional nitrogen-fixing symbiosis. Therefore, the P(II) protein affects both Rhizobium nitrogen metabolism and alfalfa nodule development.
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Affiliation(s)
- T Arcondéguy
- Unité Mixte de Recherches (UMR) 215 Institut National de la Recherche Agronomique (INRA)/Centre National de la Recherche Scientifique (CNRS), Castanet-Tolosan, France
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40
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Abstract
Soil bacteria of the genera Azorhizobium, Bradyrhizobium, and Rhizobium are collectively termed rhizobia. They share the ability to penetrate legume roots and elicit morphological responses that lead to the appearance of nodules. Bacteria within these symbiotic structures fix atmosphere nitrogen and thus are of immense ecological and agricultural significance. Although modern genetic analysis of rhizobia began less than 20 years ago, dozens of nodulation genes have now been identified, some in multiple species of rhizobia. These genetic advances have led to the discovery of a host surveillance system encoded by nodD and to the identification of Nod factor signals. These derivatives of oligochitin are synthesized by the protein products of nodABC, nodFE, NodPQ, and other nodulation genes; they provoke symbiotic responses on the part of the host and have generated immense interest in recent years. The symbiotic functions of other nodulation genes are nonetheless uncertain, and there remain significant gaps in our knowledge of several large groups of rhizobia with interesting biological properties. This review focuses on the nodulation genes of rhizobia, with particular emphasis on the concept of biological specificity of symbiosis with legume host plants.
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Affiliation(s)
- S G Pueppke
- Department of Plant Pathology, University of Missouri, Columbia, MO 65211, USA
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41
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Plazanet C, Réfrégier G, Demont N, Truchet G, Rosenberg C. The Rhizobium meliloti region located downstream of the nod box n6 is involved in the specific nodulation of Medicago lupulina. FEMS Microbiol Lett 1995; 133:285-91. [PMID: 8522144 DOI: 10.1111/j.1574-6968.1995.tb07898.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Six nod box regulatory sequences are present in the Rhizobium meliloti genome. We have analysed the DNA region located downstream of nod box n6, and identified three open reading frames, designated nolQa, nolQb and nolS. LacZ fusions in these ORFs are not induced by classical nod gene inducers, which indicates that their expression either is not under the control of the nod box, or involves another regulatory mechanism acting in conjunction with the NodD/nod box regulatory circuit. Mutations in this n6 locus result in a delay in nodule formation on a particular host, Medicago lupulina. As this region is not strictly conserved among different R. meliloti strains, nolQa, nolQb and nolS may constitute auxiliary nodulation genes, for which the selection pressure is limited to particular host plants.
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Affiliation(s)
- C Plazanet
- Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, CNRS-INRA, Castanet-Tolosan, France
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42
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Fellay R, Perret X, Viprey V, Broughton WJ, Brenner S. Organization of host-inducible transcripts on the symbiotic plasmid of Rhizobium sp. NGR234. Mol Microbiol 1995; 16:657-67. [PMID: 7476161 DOI: 10.1111/j.1365-2958.1995.tb02428.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In a systematic approach to identify genes involved in the early steps of the legume-Rhizobium symbiosis, we studied transcription patterns of symbiotic plasmid-borne loci. A competitive hybridization procedure was used to identify DNA restriction fragments carrying genes whose expression is enhanced by plant root exudates or by purified flavonoids. Fragments containing induced genes were then located on the physical map of the 500 kb pNGR234a. New inducible loci as well as previously described genes were identified and their time course of induction determined. After initial induction, transcription of loci such as nodABC and the host-specificity genes nodSU decreased to undetectable levels 24 h after incubation with purified flavonoids. In contrast, expression of other loci is detectable only after several hours of induction. Surprisingly, many genes remained transcribed in the nodD1- mutant suggesting the presence of other flavonoid-dependent activators in NGR234. The hsnl region, which is involved in host specificity, was shown to carry several inducible but independently regulated transcripts. Sequencing analysis revealed several open reading frames whose products, based on sequence similarities, may be involved in L-fucose metabolism and its adjunction to the Nod factors.
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Affiliation(s)
- R Fellay
- Laboratoire de Biologie Moléculaire des Plantes Supérieures, Université de Genève, Switzerland
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43
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Abstract
Rhizobium, Bradyrhizobium, and Azorhizobium species are able to elicit the formation of unique structures, called nodules, on the roots or stems of the leguminous host. In these nodules, the rhizobia convert atmospheric N2 into ammonia for the plant. To establish this symbiosis, signals are produced early in the interaction between plant and rhizobia and they elicit discrete responses by the two symbiotic partners. First, transcription of the bacterial nodulation (nod) genes is under control of the NodD regulatory protein, which is activated by specific plant signals, flavonoids, present in the root exudates. In return, the nod-encoded enzymes are involved in the synthesis and excretion of specific lipooligosaccharides, which are able to trigger on the host plant the organogenic program leading to the formation of nodules. An overview of the organization, regulation, and function of the nod genes and their participation in the determination of the host specificity is presented.
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Affiliation(s)
- P van Rhijn
- F.A. Janssens Laboratory of Genetics, KU Leuven, Heverlee, Belgium
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44
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Ardourel M, Demont N, Debellé F, Maillet F, de Billy F, Promé JC, Dénarié J, Truchet G. Rhizobium meliloti lipooligosaccharide nodulation factors: different structural requirements for bacterial entry into target root hair cells and induction of plant symbiotic developmental responses. THE PLANT CELL 1994; 6:1357-74. [PMID: 7994171 PMCID: PMC160526 DOI: 10.1105/tpc.6.10.1357] [Citation(s) in RCA: 145] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Rhizobium meliloti produces lipochitooligosaccharide nodulation NodRm factors that are required for nodulation of legume hosts. NodRm factors are O-acetylated and N-acylated by specific C16-unsaturated fatty acids. nodL mutants produce non-O-acetylated factors, and nodFE mutants produce factors with modified acyl substituents. Both mutants exhibited a significantly reduced capacity to elicit infection thread (IT) formation in alfalfa. However, once initiated, ITs developed and allowed the formation of nitrogen-fixing nodules. In contrast, double nodF/nodL mutants were unable to penetrate into legume hosts and to form ITs. Nevertheless, these mutants induced widespread cell wall tip growth in trichoblasts and other epidermal cells and were also able to elicit cortical cell activation at a distance. NodRm factor structural requirements are thus clearly more stringent for bacterial entry than for the elicitation of developmental plant responses.
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Affiliation(s)
- M Ardourel
- Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, CNRS-INRA, Castanet-Tolosan, France
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45
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Margolin W, Long SR. Rhizobium meliloti contains a novel second homolog of the cell division gene ftsZ. J Bacteriol 1994; 176:2033-43. [PMID: 8144471 PMCID: PMC205309 DOI: 10.1128/jb.176.7.2033-2043.1994] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
We have identified a second homolog of the cell division gene, ftsZ, in the endosymbiont Rhizobium meliloti. The ftsZ2 gene was cloned by screening a genomic lambda library with a probe derived from PCR amplification of a highly conserved domain. It encodes a 36-kDa protein which shares a high level of sequence similarity with the FtsZ proteins of Escherichia coli and Bacillus subtilis and FtsZ1 (Z1) of R. meliloti but lacks the carboxy-terminal region conserved in other FtsZ proteins. The identity of the ftsZ2 gene product was confirmed both by in vitro transcription-translation in an R. meliloti S-30 extract and by overproduction in R. meliloti cells. As with Z1, the overproduction of FtsZ2 in E. coli inhibited cell division and induced filamentation, although to a lesser extent than with Z1. However, the expression of ftsZ2 in E. coli under certain conditions caused some cells to coil dramatically, a phenotype not observed during Z1 overproduction. Although several Tn3-GUS (glucuronidase) insertions in a plasmid-borne ftsZ2 gene failed to cross into the chromosome, one interruption in the chromosomal ftsZ2 gene was isolated, suggesting that ftsZ2 is nonessential for viability. The two ftsZ genes were genetically mapped to the R. meliloti main chromosome, approximately 100 kb apart.
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Affiliation(s)
- W Margolin
- Department of Biological Sciences, Stanford University, California 94305-5020
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46
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Affiliation(s)
- H I McKhann
- Department of Biology, University of California, Los Angeles 90024-1606
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47
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Cell and Molecular Biology of Rhizobium-Plant. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/s0074-7696(08)62252-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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48
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Dusha I, Kondorosi A. Genes at different regulatory levels are required for the ammonia control of nodulation in Rhizobium meliloti. MOLECULAR & GENERAL GENETICS : MGG 1993; 240:435-44. [PMID: 8413194 DOI: 10.1007/bf00280398] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The expression of the nodulation genes nodABC of Rhizobium meliloti, which determine early response functions to plant host signals, is regulated by the level of ammonia, the primary product of symbiotic nitrogen fixation. We show that the pathway that links the ammonia-induced signal to the transcriptional control of the nodABC genes involves at least two regulatory levels. The fluctuating nitrogen level is sensed and the signal is mediated by the members of the general nitrogen regulatory (ntr) system, then transmitted to the syrM-nodD3 genes representing the nod-specific level of ammonia regulation. At low ammonia concentration, the activator protein NtrC exerts its effect via nodD3. In conditions of nitrogen excess ntrR, involved in the repression of nod genes, may function in coordination with the syrM gene. Finally, the NodD3 protein may relay the nitrogen status signal to the transcriptional control of the nodABC genes.
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Affiliation(s)
- I Dusha
- Institute of Genetics, Biological Research Center of Hungarian Academy of Sciences, Szeged
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Demont N, Debellé F, Aurelle H, Dénarié J, Promé J. Role of the Rhizobium meliloti nodF and nodE genes in the biosynthesis of lipo-oligosaccharidic nodulation factors. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(20)80704-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Abstract
The early steps of symbiotic nodule formation by Rhizobium on plants require coordinate expression of several nod gene operons, which is accomplished by the activating protein NodD. Three different NodD proteins are encoded by Sym plasmid genes in Rhizobium meliloti, the alfalfa symbiont. NodD1 and NodD2 activate nod operons when Rhizobium is exposed to host plant inducers. The third, NodD3, is an inducer-independent activator of nod operons. We previously observed that nodD3 carried on a multicopy plasmid required another closely linked gene, syrM, for constitutive nod operon expression. Here, we show that syrM activates expression of the nodD3 gene, and that nodD3 activates expression of syrM. The two genes constitute a self-amplifying positive regulatory circuit in both cultured Rhizobium and cells within the symbiotic nodule. We find little effect of plant inducers on the circuit or on expression of nodD3 carried on pSyma. This regulatory circuit may be important for regulation of nod genes within the developing nodule.
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Affiliation(s)
- J A Swanson
- Department of Biological Sciences, Stanford University, California 94305-5020
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