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Rosenblueth M, Ormeño-Orrillo E, López-López A, Rogel MA, Reyes-Hernández BJ, Martínez-Romero JC, Reddy PM, Martínez-Romero E. Nitrogen Fixation in Cereals. Front Microbiol 2018; 9:1794. [PMID: 30140262 PMCID: PMC6095057 DOI: 10.3389/fmicb.2018.01794] [Citation(s) in RCA: 100] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Accepted: 07/17/2018] [Indexed: 01/30/2023] Open
Abstract
Cereals such as maize, rice, wheat and sorghum are the most important crops for human nutrition. Like other plants, cereals associate with diverse bacteria (including nitrogen-fixing bacteria called diazotrophs) and fungi. As large amounts of chemical fertilizers are used in cereals, it has always been desirable to promote biological nitrogen fixation in such crops. The quest for nitrogen fixation in cereals started long ago with the isolation of nitrogen-fixing bacteria from different plants. The sources of diazotrophs in cereals may be seeds, soils, and even irrigation water and diazotrophs have been found on roots or as endophytes. Recently, culture-independent molecular approaches have revealed that some rhizobia are found in cereal plants and that bacterial nitrogenase genes are expressed in plants. Since the levels of nitrogen-fixation attained with nitrogen-fixing bacteria in cereals are not high enough to support the plant’s needs and never as good as those obtained with chemical fertilizers or with rhizobium in symbiosis with legumes, it has been the aim of different studies to increase nitrogen-fixation in cereals. In many cases, these efforts have not been successful. However, new diazotroph mutants with enhanced capabilities to excrete ammonium are being successfully used to promote plant growth as commensal bacteria. In addition, there are ambitious projects supported by different funding agencies that are trying to genetically modify maize and other cereals to enhance diazotroph colonization or to fix nitrogen or to form nodules with nitrogen-fixing symbiotic rhizobia.
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Affiliation(s)
- Mónica Rosenblueth
- Center for Genomic Sciences, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Ernesto Ormeño-Orrillo
- Laboratorio de Ecología Microbiana y Biotecnología, Departamento de Biología, Facultad de Ciencias, Universidad Nacional Agraria La Molina, Lima, Peru
| | - Aline López-López
- Centro de Investigación en Genética y Ambiente, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico
| | - Marco A Rogel
- Center for Genomic Sciences, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | | | | | - Pallavolu M Reddy
- The Energy and Resources Institute, India Habitat Centre, New Delhi, India
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Küster N, Rosahl S, Dräger B. Potato plants with genetically engineered tropane alkaloid precursors. PLANTA 2017; 245:355-365. [PMID: 27783159 DOI: 10.1007/s00425-016-2610-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Accepted: 10/17/2016] [Indexed: 06/06/2023]
Abstract
Solanum tuberosum tropinone reductase I reduced tropinone in vivo. Suppression of tropinone reductase II strongly reduced calystegines in sprouts. Overexpression of putrescine N -methyltransferase did not alter calystegine accumulation. Calystegines are hydroxylated alkaloids formed by the tropane alkaloid pathway. They accumulate in potato (Solanum tuberosum L., Solanaceae) roots and sprouting tubers. Calystegines inhibit various glycosidases in vitro due to their sugar-mimic structure, but functions of calystegines in plants are not understood. Enzymes participating in or competing with calystegine biosynthesis, including putrescine N-methyltransferase (PMT) and tropinone reductases (TRI and TRII), were altered in their activity in potato plants by RNA interference (RNAi) and by overexpression. The genetically altered potato plants were investigated for the accumulation of calystegines and for intermediates of their biosynthesis. An increase in N-methylputrescine provided by DsPMT expression was not sufficient to increase calystegine accumulation. Overexpression and gene knockdown of StTRI proved that S. tuberosum TRI is a functional tropinone reductase in vivo, but no influence on calystegine accumulation was observed. When StTRII expression was suppressed by RNAi, calystegine formation was severely compromised in the transformed plants. Under phytochamber and green house conditions, the StTRII RNAi plants did not show phenotypic alterations. Further investigation of calystegines function in potato plants under natural conditions is enabled by the calystegine deprived StTRII RNAi plants.
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Affiliation(s)
- Nadine Küster
- Department of Pharmaceutical Biology, Martin-Luther University Halle-Wittenberg, Hoher Weg 8, 06120, Halle (Saale), Germany
| | - Sabine Rosahl
- Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120, Halle (Saale), Germany
| | - Birgit Dräger
- Department of Pharmaceutical Biology, Martin-Luther University Halle-Wittenberg, Hoher Weg 8, 06120, Halle (Saale), Germany.
- University Leipzig, Ritterstraße 26, 04109, Leipzig, Germany.
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Ormeño-Orrillo E, Martínez-Romero E. Phenotypic tests in Rhizobium species description: An opinion and (a sympatric speciation) hypothesis. Syst Appl Microbiol 2013; 36:145-7. [DOI: 10.1016/j.syapm.2012.11.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 11/23/2012] [Accepted: 11/27/2012] [Indexed: 10/27/2022]
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Genome Sequence of Sinorhizobium meliloti Rm41. GENOME ANNOUNCEMENTS 2013; 1:genomeA00013-12. [PMID: 23405285 PMCID: PMC3556828 DOI: 10.1128/genomea.00013-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 10/17/2012] [Indexed: 11/26/2022]
Abstract
Sinorhizobium meliloti Rm41 nodulates alfalfa plants, forming indeterminate type nodules. It is characterized by a strain-specific K-antigen able to replace exopolysaccharides in promotion of nodule invasion. We present the Rm41 genome, composed of one chromosome, the chromid pSymB, the megaplasmid pSymA, and the nonsymbiotic plasmid pRme41a.
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López-Guerrero MG, Ormeño-Orrillo E, Acosta JL, Mendoza-Vargas A, Rogel MA, Ramírez MA, Rosenblueth M, Martínez-Romero J, Martínez-Romero E. Rhizobial extrachromosomal replicon variability, stability and expression in natural niches. Plasmid 2012; 68:149-58. [PMID: 22813963 DOI: 10.1016/j.plasmid.2012.07.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 06/28/2012] [Accepted: 07/06/2012] [Indexed: 12/25/2022]
Abstract
In bacteria, niche adaptation may be determined by mobile extrachromosomal elements. A remarkable characteristic of Rhizobium and Ensifer (Sinorhizobium) but also of Agrobacterium species is that almost half of the genome is contained in several large extrachromosomal replicons (ERs). They encode a plethora of functions, some of them required for bacterial survival, niche adaptation, plasmid transfer or stability. In spite of this, plasmid loss is common in rhizobia upon subculturing. Rhizobial gene-expression studies in plant rhizospheres with novel results from transcriptomic analysis of Rhizobium phaseoli in maize and Phaseolus vulgaris roots highlight the role of ERs in natural niches and allowed the identification of common extrachromosomal genes expressed in association with plant rootlets and the replicons involved.
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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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Affiliation(s)
- Stefan Biastoff
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, 06120 Halle/Saale, Germany
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Shaw LJ, Morris P, Hooker JE. Perception and modification of plant flavonoid signals by rhizosphere microorganisms. Environ Microbiol 2006; 8:1867-80. [PMID: 17014487 DOI: 10.1111/j.1462-2920.2006.01141.x] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Flavonoids are a diverse class of polyphenolic compounds that are produced as a result of plant secondary metabolism. They are known to play a multifunctional role in rhizospheric plant-microbe and plant-plant communication. Most familiar is their function as a signal in initiation of the legume-rhizobia symbiosis, but, flavonoids may also be signals in the establishment of arbuscular mycorrhizal symbiosis and are known agents in plant defence and in allelopathic interactions. Flavonoid perception by, and impact on, their microbial targets (e.g. rhizobia, plant pathogens) is relatively well characterized. However, potential impacts on 'non-target' rhizosphere inhabitants ('non-target' is used to distinguish those microorganisms not conventionally known as targets) have not been thoroughly investigated. Thus, this review first summarizes the conventional roles of flavonoids as nod gene inducers, phytoalexins and allelochemicals before exploring questions concerning 'non-target' impacts. We hypothesize that flavonoids act to shape rhizosphere microbial community structure because they represent a potential source of carbon and toxicity and that they impact on rhizosphere function, for example, by accelerating the biodegradation of xenobiotics. We also examine the reverse question, 'how do rhizosphere microbial communities impact on flavonoid signals?' The presence of microorganisms undoubtedly influences the quality and quantity of flavonoids present in the rhizosphere, both through modification of root exudation patterns and microbial catabolism of exudates. Microbial alteration and attenuation of flavonoid signals may have ecological consequences for below-ground plant-microbe and plant-plant interaction. We have a lack of knowledge concerning the composition, concentration and bioavailability of flavonoids actually experienced by microbes in an intact rhizosphere, but this may be addressed through advances in microspectroscopic and biosensor techniques. Through the use of plant mutants defective in flavonoid biosynthesis, we may also start to address the question of the significance of flavonoids in shaping rhizosphere community structure and function.
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Affiliation(s)
- Liz J Shaw
- Department of Environmental and Geographical Sciences, Manchester Metropolitan University, John Dalton Building, Chester Street, M1 5GD, UK.
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Yost CK, Rath AM, Noel TC, Hynes MF. Characterization of genes involved in erythritol catabolism in Rhizobium leguminosarum bv. viciae. MICROBIOLOGY-SGM 2006; 152:2061-2074. [PMID: 16804181 DOI: 10.1099/mic.0.28938-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A genetic locus encoding erythritol uptake and catabolism genes was identified in Rhizobium leguminosarum bv. viciae, and shown to be plasmid encoded in a wide range of R. leguminosarum strains. A Tn5-B22 mutant (19B-3) unable to grow on erythritol was isolated from a mutant library of R. leguminosarum strain VF39SM. The mutated gene eryF was cloned and partially sequenced, and determined to have a high homology to permease genes of ABC transporters. A cosmid complementing the mutation (pCos42) was identified and was shown to carry all the genes necessary to restore the ability to grow on erythritol to a VF39SM strain cured of pRleVF39f. In the genomic DNA sequence of strain 3841, the gene linked to the mutation in 19B-3 is flanked by a cluster of genes with high homology to the known erythritol catabolic genes from Brucella spp. Through mutagenesis studies, three distinct operons on pCos42 that are required for growth on erythritol were identified: an ABC-transporter operon (eryEFG), a catabolic operon (eryABCD) and an operon (deoR-tpiA2-rpiB) that encodes a gene with significant homology to triosephosphate isomerase (tpiA2). These genes all share high sequence identity to genes in the erythritol catabolism region of Brucella spp., and clustalw alignments suggest that horizontal transfer of the erythritol locus may have occurred between R. leguminosarum and Brucella. Transcription of the eryABCD operon is repressed by EryD and is induced by the presence of erythritol. Mutant 19B-3 was impaired in its ability to compete against wild-type for nodulation of pea plants but was still capable of forming nitrogen-fixing nodules.
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Affiliation(s)
- Christopher K Yost
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
| | - Amber M Rath
- Department of Biology, University of Calgary, 2500 University Drive, Calgary, AB T2N 1N4, Canada
| | - Tanya C Noel
- Department of Biology, University of Calgary, 2500 University Drive, Calgary, AB T2N 1N4, Canada
| | - Michael F Hynes
- Department of Biology, University of Calgary, 2500 University Drive, Calgary, AB T2N 1N4, Canada
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Prell J, Poole P. Metabolic changes of rhizobia in legume nodules. Trends Microbiol 2006; 14:161-8. [PMID: 16520035 DOI: 10.1016/j.tim.2006.02.005] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 02/06/2006] [Accepted: 02/21/2006] [Indexed: 12/01/2022]
Abstract
Bacteria have evolved a wide variety of metabolic strategies to cope with varied environments. Some are specialists and only able to survive in restricted environments; others are generalists and able to cope with diverse environmental conditions. Rhizobia (e.g. Rhizobium, Sinorhizobium, Bradyrhizobium, Mesorhizobium and Azorhizobium species) can survive and compete for nutrients in soil and the plant rhizosphere but can also form a beneficial symbiosis with legumes in a highly specialized plant cell environment. Inside the legume-root nodule, the bacteria (bacteroids) reduce dinitrogen to ammonium, which is secreted to the plant in exchange for a carbon and energy source. A new and challenging aspect of nodule physiology is that nitrogen fixation requires the cycling of amino acids between the bacteroid and plant. This review aims to summarize the metabolic plasticity of rhizobia and the importance of amino acid cycling.
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Affiliation(s)
- Juergen Prell
- School of Biological Sciences, University of Reading, UK, RG6 6AJ
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Höke D, Dräger B. Calystegines in Calystegia sepium do not inhibit fungal growth and invertase activity but interact with plant invertase. PLANT BIOLOGY (STUTTGART, GERMANY) 2004; 6:206-213. [PMID: 15045673 DOI: 10.1055/s-2004-817797] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Calystegines are alkaloidal glycosidase inhibitors. They accumulate predominantly in young and meristemic parts of Calystegia sepium (Convolvulaceae). C. sepium, bindweed, infests meadows and cereal fields and is difficult to control chemically. Fungal pathogens against C. sepium are established as mycoherbicides. Stagonospora convolvuli LA39 attacks C. sepium and does not affect crop plants, but young plants of C. sepium are less susceptible to the fungus. The interaction of Stagonospora convolvuli with calystegines was investigated. Further, endophytic fungi of several classes were isolated from wild-grown Calystegia sepium leaves, and selected strains were tested for interaction with calystegines. Fungal growth on agar containing calystegines was not affected considerably. Plants in climate chambers were infected with an endophyte, Phomopsis, and with the fungal pathogen, Stagonospora convolvuli. Calystegine levels were measured in infected and non-infected plant tissues. Accumulation depended on developmental stage of the plant tissue and was not influenced by infection. Acid invertase was measured from fungal mycelia and from infected and non-infected plant tissues. Fungal acid invertase activity was not inhibited by 10 mM calystegine B (2), while invertase from C. sepium leaves was inhibited. It is concluded that calystegines do not inhibit fungal development and sucrose consumption under the conditions of the present investigation, but may act by redirection of plant carbohydrate metabolism.
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Affiliation(s)
- D Höke
- Institute of Pharmaceutical Biology, Faculty of Pharmacy, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
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