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A signal cascade originated from epidermis defines apical-basal patterning of Arabidopsis shoot apical meristems. Nat Commun 2020; 11:1214. [PMID: 32139673 PMCID: PMC7058014 DOI: 10.1038/s41467-020-14989-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 02/11/2020] [Indexed: 11/22/2022] Open
Abstract
In multicellular organisms, a long-standing question is how spatial patterns of distinct cell types are initiated and maintained during continuous cell division and proliferation. Along the vertical axis of plant shoot apical meristems (SAMs), stem cells are located at the top while cells specifying the stem cells are located more basally, forming a robust apical-basal pattern. We previously found that in Arabidopsis SAMs, the HAIRY MERISTEM (HAM) family transcription factors form a concentration gradient from the epidermis to the interior cell layers, and this gradient is essential for the stem cell specification and the apical-basal patterning of the SAMs. Here, we uncover that epidermis specific transcription factors, ARABIDOPSIS THALIANA MERISTEM LAYER 1 (ATML1) and its close homolog, define the concentration gradient of HAM in the SAM through activating a group of microRNAs. This study provides a molecular framework linking the epidermis-derived signal to the stem cell homeostasis in plants. A concentration gradient of HAM transcription factors specifies apical-basal patterning in the Arabidopsis shoot apical meristem. Here, the authors show that epidermal expression of the ATML1 transcription factor defines this concentration gradient via activation of mobile micro RNA.
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Assembly and transfer of tripartite integrative and conjugative genetic elements. Proc Natl Acad Sci U S A 2016; 113:12268-12273. [PMID: 27733511 DOI: 10.1073/pnas.1613358113] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Integrative and conjugative elements (ICEs) are ubiquitous mobile genetic elements present as "genomic islands" within bacterial chromosomes. Symbiosis islands are ICEs that convert nonsymbiotic mesorhizobia into symbionts of legumes. Here we report the discovery of symbiosis ICEs that exist as three separate chromosomal regions when integrated in their hosts, but through recombination assemble as a single circular ICE for conjugative transfer. Whole-genome comparisons revealed exconjugants derived from nonsymbiotic mesorhizobia received three separate chromosomal regions from the donor Mesorhizobium ciceri WSM1271. The three regions were each bordered by two nonhomologous integrase attachment (att) sites, which together comprised three homologous pairs of attL and attR sites. Sequential recombination between each attL and attR pair produced corresponding attP and attB sites and joined the three fragments to produce a single circular ICE, ICEMcSym1271 A plasmid carrying the three attP sites was used to recreate the process of tripartite ICE integration and to confirm the role of integrase genes intS, intM, and intG in this process. Nine additional tripartite ICEs were identified in diverse mesorhizobia and transfer was demonstrated for three of them. The transfer of tripartite ICEs to nonsymbiotic mesorhizobia explains the evolution of competitive but suboptimal N2-fixing strains found in Western Australian soils. The unheralded existence of tripartite ICEs raises the possibility that multipartite elements reside in other organisms, but have been overlooked because of their unusual biology. These discoveries reveal mechanisms by which integrases dramatically manipulate bacterial genomes to allow cotransfer of disparate chromosomal regions.
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Kelly S, Sullivan J, Ronson C, Tian R, Bräu L, Davenport K, Daligault H, Erkkila T, Goodwin L, Gu W, Munk C, Teshima H, Xu Y, Chain P, Woyke T, Liolios K, Pati A, Mavromatis K, Markowitz V, Ivanova N, Kyrpides N, Reeve W. Genome sequence of the Lotus spp. microsymbiont Mesorhizobium loti strain NZP2037. Stand Genomic Sci 2014; 9:7. [PMID: 25780500 PMCID: PMC4334872 DOI: 10.1186/1944-3277-9-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 06/16/2014] [Indexed: 12/04/2022] Open
Abstract
Mesorhizobium loti strain NZP2037 was isolated in 1961 in Palmerston North, New Zealand from a Lotus divaricatus root nodule. Compared to most other M. loti strains, it has a broad host range and is one of very few M. loti strains able to form effective nodules on the agriculturally important legume Lotus pedunculatus. NZP2037 is an aerobic, Gram negative, non-spore-forming rod. This report reveals that the genome of M. loti strain NZP2037 does not harbor any plasmids and contains a single scaffold of size 7,462,792 bp which encodes 7,318 protein-coding genes and 70 RNA-only encoding genes. This rhizobial genome is one of 100 sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.
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Affiliation(s)
- Simon Kelly
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - John Sullivan
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Clive Ronson
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Rui Tian
- Centre for Rhizobium Studies, Murdoch University, Murdoch, Perth, Australia
| | - Lambert Bräu
- School of Life and Environmental Sciences, Deakin University, Deakin, Victoria, Australia
| | - Karen Davenport
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Hajnalka Daligault
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Tracy Erkkila
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Lynne Goodwin
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Wei Gu
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Christine Munk
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Hazuki Teshima
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Yan Xu
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Patrick Chain
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, NM, USA
| | - Tanja Woyke
- DOE Joint Genome Institute, Walnut Creek, CA, USA
| | | | - Amrita Pati
- DOE Joint Genome Institute, Walnut Creek, CA, USA
| | - Konstantinos Mavromatis
- 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
| | | | - Nikos Kyrpides
- DOE Joint Genome Institute, Walnut Creek, CA, USA ; Department of Biological Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Wayne Reeve
- Centre for Rhizobium Studies, Murdoch University, Murdoch, Perth, Australia
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Sullivan JT, Patrick HN, Lowther WL, Scott DB, Ronson CW. Nodulating strains of Rhizobium loti arise through chromosomal symbiotic gene transfer in the environment. Proc Natl Acad Sci U S A 1995; 92:8985-9. [PMID: 7568057 PMCID: PMC41092 DOI: 10.1073/pnas.92.19.8985] [Citation(s) in RCA: 338] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Rhizobia were isolated from nodules off a stand of Lotus corniculatus established with a single inoculant strain, ICMP3153, 7 years earlier in an area devoid of naturalized Rhizobium loti. The isolates showed diversity in growth rate, Spe I fingerprint of genomic DNA, and hybridization pattern to genomic DNA probes. The 19% of isolates that grew at the same rate as strain ICMP3153 were the only isolates that had the same fingerprint as strain ICMP3153. Sequencing of part of the 16S rRNA gene of several diverse isolates confirmed that they were not derived from the inoculant strain. Nevertheless, all non-ICMP3153 strains gave EcoRI and Spe I hybridization patterns identical to ICMP3153 when hybridized to nodulation gene cosmids. Hybridization of digests generated by the very rare cutting enzyme Swa I revealed that the symbiotic DNA region (at least 105 kb) was chromosomally integrated in the strains. The results suggest that the diverse strains arose by transfer of chromosomal symbiotic genes from ICMP3153 to nonsymbiotic rhizobia in the environment.
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MESH Headings
- Base Sequence
- Blotting, Southern
- Chromosomes, Bacterial/genetics
- Conserved Sequence
- DNA, Bacterial/genetics
- DNA, Ribosomal/genetics
- Electrophoresis, Gel, Pulsed-Field
- Gene Transfer Techniques
- Genes, Bacterial
- Molecular Sequence Data
- Nitrogen Fixation
- Plant Roots/microbiology
- Plasmids/genetics
- RNA, Bacterial/genetics
- RNA, Ribosomal, 16S/genetics
- Restriction Mapping
- Rhizobium/genetics
- Rhizobium/isolation & purification
- Sequence Analysis, DNA
- Symbiosis/genetics
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Affiliation(s)
- J T Sullivan
- Department of Microbiology, University of Otago, Dunedin, New Zealand
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Dowling DN, Samrey U, Stanley J, Broughton WJ. Cloning of Rhizobium leguminosarum genes for competitive nodulation blocking on peas. J Bacteriol 1987; 169:1345-8. [PMID: 3546272 PMCID: PMC211944 DOI: 10.1128/jb.169.3.1345-1348.1987] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
One type of competitive interaction among rhizobia is that between nonnodulating and nodulating strains of Rhizobium leguminosarum on primitive pea genotypes. Pisum sativum cv. Afghanistan nodulates effectively with R. leguminosarum TOM, and this can be blocked in mixed inoculations by R. leguminosarum PF2, which does not nodulate this cultivar. We termed this PF2 phenotype Cnb+, for competitive nodulation blocking. Strain PF2 contains three large plasmids including a 250-kilobase-pair symbiotic (Sym) plasmid. Transfer of this plasmid, pSymPF2, to nonblocking rhizobia conferred the Cnb+ phenotype on recipients in mixed inoculations on cultivar Afghanistan with TOM. A library of the PF2 genome constructed in the vector pMMB33 was used to isolate two cosmid clones which hybridize to pSymPF2. These cosmids, pDD50 and pDD58, overlapped to the extent of 23 kilobase pairs and conferred a Cnb+ phenotype on recipient Cnb- rhizobia, as did pSD1, a subclone from the common region.
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Scott DB, Wilson R, Shaw GJ, Petit A, Tempe J. Biosynthesis and degradation of nodule-specific Rhizobium loti compounds in Lotus nodules. J Bacteriol 1987; 169:278-82. [PMID: 3025173 PMCID: PMC211764 DOI: 10.1128/jb.169.1.278-282.1987] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Two nodule-specific Rhizobium loti compounds were identified in Lotus tenuis and Lotus pedunculatus nodules induced by strain NZP2037. One, a silver nitrate-positive cation called rhizolotine, has been characterized as the riboside of a novel alpha-hydroxyimino acid containing a 1,4,5,6-tetrahydropyrimidine ring (G. J. Shaw, R. D. Wilson, G. A. Lane, L. D. Kennedy, D. B. Scott, and G. J. Gainsford, J. Chem. Soc. Chem. Commun., p. 180-181, 1986), and the other, yellow-1, stains yellow with ninhydrin. Both compounds were degraded by R. loti NZP2037 but not by strains of Rhizobium meliloti, Rhizobium trifolii, or Agrobacterium tumefaciens. Under the conditions tested neither compound was able to serve as a sole source of C or N for growth of R. loti NZP2037. Rhizolotine and yellow-1 were found in nodules from a range of different legumes inoculated with NZP2037, suggesting that the Rhizobium and not the host plant determines their synthesis. Neither compound was found in nodulelike structures of L. pedunculatus induced by transposon Tn5-induced noninfectious (Inf-) mutants of NZP2037 or in similar structures induced by a transconjugant of NZP2037 containing the symbiotic (Sym) cointegrate plasmid pPN1 of R. trifolii. Both compounds were also absent in the ineffective nodules induced by the bacterial-release-negative (Bar-) mutant, strain PN239. However, both compounds were present in nodules induced by the fixation-negative (Fix-) mutant PN235 and in Fix+ nodules formed by a plasmid-cured derivative of NZP2037. These results would suggest that infection and bacterial release from the infection thread are necessary for nodule (symbiotic) synthesis of these compounds.
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Broughton WJ, Wong CH, Lewin A, Samrey U, Myint H, Meyer H, Dowling DN, Simon R. Identification of Rhizobium plasmid sequences involved in recognition of Psophocarpus, Vigna, and other legumes. J Biophys Biochem Cytol 1986; 102:1173-82. [PMID: 3958042 PMCID: PMC2114177 DOI: 10.1083/jcb.102.4.1173] [Citation(s) in RCA: 71] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Symbiotic DNA sequences involved in nodulation by Rhizobium must include genes responsible for recognizing homologous hosts. We sought these genes by mobilizing the symbiotic plasmid of a broad host-range Rhizobium MPIK3030 (= NGR234) that can nodulate Glycine max, Psophocarpus tetragonolobus, Vigna unguiculata, etc., into two Nod- Rhizobium mutants as well as into Agrobacterium tumefaciens. Subsequently, cosmid clones of pMPIK3030a were mobilized into Nod+ Rhizobium that cannot nodulate the chosen hosts. Nodule development was monitored by examining the ultrastructure of nodules formed by the transconjugants. pMPIK3030a could complement Nod- and Nif- deletions in R. leguminosarum and R. meliloti as well as enable A. tumefaciens to nodulate. Three non-overlapping sets of cosmids were found that conferred upon a slow-growing Rhizobium species, as well as on R. loti and R. meliloti, the ability to nodulate Psophocarpus and Vigna, thus pointing to the existence of three sets of host-specificity genes. Recipients harboring these hsn regions had truly broadened host-range since they could nodulate both their original hosts as well as MPIK3030 hosts.
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Isolation and characterization of transposon Tn5-induced symbiotic mutants of Rhizobium loti. J Bacteriol 1985; 162:335-43. [PMID: 2984178 PMCID: PMC218994 DOI: 10.1128/jb.162.1.335-343.1985] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Rhizobium loti NZP2037 and NZP2213, each cured of its single large indigenous plasmid, formed effective nodules on Lotus spp., suggesting that the symbiotic genes are carried on the chromosome of these strains. By using pSUP1011 as a vector for introducing transposon Tn5 into R. loti NZP2037, symbiotic mutants blocked in hair curling (Hac), nodule initiation (Noi), bacterial release (Bar), and nitrogen fixation (Nif/Cof) on Lotus pedunculatus were isolated. Cosmids complementing the Hac, Noi, and Bar mutants were isolated from a pLAFR1 gene library of NZP2037 DNA by in planta complementation and found to contain EcoRI fragments of identical sizes to those into which Tn5 had inserted in the mutants. The cosmids that complemented the mutants of these phenotypic classes did not share common fragments, nor did cosmids that complemented four mutants within the Noi class, suggesting that these symbiotically important regions are not tightly linked on the R. loti chromosome.
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