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Merfa MV, Naranjo E, Shantharaj D, De La Fuente L. Growth of ' Candidatus Liberibacter asiaticus' in Commercial Grapefruit Juice-Based Media Formulations Reveals Common Cell Density-Dependent Transient Behaviors. PHYTOPATHOLOGY 2022; 112:131-144. [PMID: 34340531 DOI: 10.1094/phyto-06-21-0228-fi] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The phloem-restricted, insect-transmitted bacterium 'Candidatus Liberibacter asiaticus' (CLas) is associated with huanglongbing (HLB), the most devastating disease of citrus worldwide. The inability to culture CLas impairs the understanding of its virulence mechanisms and the development of effective management strategies to control this incurable disease. Previously, our research group used commercial grapefruit juice (GJ) to prolong the viability of CLas in vitro. In the present study, GJ was amended with a wide range of compounds and incubated under different conditions to optimize CLas growth. Remarkably, results showed that CLas growth ratios were inversely proportional to the initial inoculum concentration. This correlation is probably regulated by a cell density-dependent mechanism, because diluting samples between subcultures allowed CLas to resume growth. Moreover, strategies to reduce the cell density of CLas, such as subculturing at short intervals and incubating samples under flow conditions, allowed this bacterium to multiply and reach maximum growth as early as 3 days after inoculation, although no sustained exponential growth was observed under any tested condition. Unfortunately, cultures were only transient, because CLas lost viability over time; nevertheless, we obtained populations of about 105 genome equivalents/ml repeatedly. Finally, we established an ex vivo system to grow CLas within periwinkle calli that could be used to propagate bacterial inoculum in the lab. In this study we determined the influence of a comprehensive set of conditions and compounds on CLas growth in culture. We hope our results will help guide future efforts toward the long-sought goal of culturing CLas axenically.
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Affiliation(s)
- Marcus V Merfa
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849
| | - Eber Naranjo
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849
| | - Deepak Shantharaj
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849
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2
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Guz N, Arshad M, Cagatay NS, Dageri A, Ullah MI. Detection of Wolbachia (Rickettsiales: Anaplasmataceae) and Candidatus Liberibacter asiaticus (Rhizobiales: Rhizobiaceae) Associated With Diaphorina citri (Hemiptera: Liviidae) Collected From Citrus reticulata (Sapindales: Rutaceae) and Alternate Host, Cordia myxa (Boraginales: Boraginaceae). JOURNAL OF ECONOMIC ENTOMOLOGY 2020; 113:1486-1492. [PMID: 32207826 DOI: 10.1093/jee/toaa043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Indexed: 06/10/2023]
Abstract
The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an important insect pest of the citrus crop worldwide. It vectors the pathogen 'Candidatus Liberibacter asiaticus' (CLas) that causes a serious disease known as citrus greening. Here, we tested the infection frequency of Wolbachia and CLas from 100 D. citri individuals collected from two host plants belonging to families Rutaceae (Citrus reticulata Blanco) and Boraginaceae (Cordia myxa L.) using molecular methods. The following trend of endosymbionts infection in adult D. citri was found; 85.4% (35/41) by Wolbachia, and 19.5% (8/41) by CLas collected from C. reticulata plants and 65.4% (17/26) by Wolbachia, and 15.4% (4/26) by CLas in case of C. myxa plant. However, 61.5% (8/13) nymphs collected from C. reticulata and 20.0% (4/20) collected from C. myxa plants were infected by Wolbachia, while no nymph was infected by CLas collected from either host plants. Findings from this work represent the first report of CLas presence in D. citri feeding on C. myxa plants. By studying the presence of CLas with other endosymbiotic bacteria, future basic and applied research to develop control strategies can be prioritized.
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Affiliation(s)
- Nurper Guz
- Molecular Entomology Lab, Department of Plant Protection, Faculty of Agriculture, Ankara University, Dıskapi, Ankara, Turkey
| | - Muhammad Arshad
- Molecular Entomology Lab, Department of Plant Protection, Faculty of Agriculture, Ankara University, Dıskapi, Ankara, Turkey
- Department of Entomology, University of Sargodha, Sargodha, Pakistan
| | - Naciye Sena Cagatay
- Molecular Entomology Lab, Department of Plant Protection, Faculty of Agriculture, Ankara University, Dıskapi, Ankara, Turkey
| | - Asli Dageri
- Department of Molecular Biology and Genetics, Necmettin Erbakan University, Meram, Konya, Turkey
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3
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Feng H, Park JS, Zhai RG, Wilson ACC. microRNA-92a regulates the expression of aphid bacteriocyte-specific secreted protein 1. BMC Res Notes 2019; 12:638. [PMID: 31564246 PMCID: PMC6767646 DOI: 10.1186/s13104-019-4665-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 09/18/2019] [Indexed: 01/01/2023] Open
Abstract
OBJECTIVE Aphids harbor a nutritional obligate endosymbiont in specialized cells called bacteriocytes, which aggregate to form an organ known as the bacteriome. Aphid bacteriomes display distinct gene expression profiles that facilitate the symbiotic relationship. Currently, the mechanisms that regulate these patterns of gene expression are unknown. Recently using computational pipelines, we identified miRNAs that are conserved in expression in the bacteriomes of two aphid species and proposed that they function as important regulators of bacteriocyte gene expression. Here using a dual luciferase assay in mouse NIH/3T3 cell culture, we aimed to experimentally validate the computationally predicted interaction between Myzus persicae miR-92a and the predicted target region of M. persicae bacteriocyte-specific secreted protein 1 (SP1) mRNA. RESULTS In the dual luciferase assay, miR-92a interacted with the SP1 target region resulting in a significant downregulation of the luciferase signal. Our results demonstrate that miR-92a interacts with SP1 to alter expression in a heterologous expression system, thereby supporting our earlier assertion that miRNAs are regulators of the aphid/Buchnera symbiotic interaction.
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Affiliation(s)
- Honglin Feng
- Department of Biology, University of Miami, Coral Gables, FL, 33146, USA. .,Boyce Thompson Institute, Ithaca, NY, 14853, USA.
| | - Joun S Park
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - R Grace Zhai
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
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4
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Fisher ML, Watson DW, Osborne JA, Mochizuki H, Breen M, Schal C. Growth kinetics of endosymbiont Wolbachia in the common bed bug, Cimex lectularius. Sci Rep 2018; 8:11444. [PMID: 30061694 PMCID: PMC6065412 DOI: 10.1038/s41598-018-29682-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 07/14/2018] [Indexed: 12/19/2022] Open
Abstract
The common bed bug, Cimex lectularius harbors the endosymbiotic microorganism, Wolbachia (wCle), in a gonad-associated bacteriome as an obligate nutritional mutualist. The obligatory nature of this association suggests that all individuals in C. lectularius populations would be infected with wCle. However, studies spanning the past several decades have reported variation in both infection frequency and relative abundance of wCle in field-collected samples of bed bugs. Since the growth kinetics of wCle is poorly understood, the objective of this study was to quantify wCle over the life cycle of two strains of C. lectularius. Our results highlight that wCle is dynamic during bed bug development, changing relative to life stage, intermolt stage, and blood-fed status. These results suggest new hypotheses about the coordination of Wolbachia growth and regression with its host's physiology and endocrine events. The observed quantitative modulation of wCle during the bed bug life cycle and during periods of starvation may explain the disparities in wCle infections reported in field-collected C. lectularius.
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Affiliation(s)
- Michael L Fisher
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina, USA.
- United States Navy Medical Service Corps, Raleigh, USA.
- W.M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina, USA.
| | - David W Watson
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina, USA
| | - Jason A Osborne
- Department of Statistics, North Carolina State University, Raleigh, North Carolina, USA
| | - Hiroyuki Mochizuki
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Matthew Breen
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Coby Schal
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina, USA.
- W.M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina, USA.
- Center for Human Health and the Environment, North Carolina State University, Raleigh, North Carolina, USA.
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5
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Cassone BJ, Redinbaugh MG, Dorrance AE, Michel AP. Shifts in Buchnera aphidicola density in soybean aphids (Aphis glycines) feeding on virus-infected soybean. INSECT MOLECULAR BIOLOGY 2015; 24:422-31. [PMID: 25845267 DOI: 10.1111/imb.12170] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 01/21/2015] [Accepted: 01/26/2015] [Indexed: 06/04/2023]
Abstract
Vertically transmitted bacterial symbionts are common in arthropods. Aphids undergo an obligate symbiosis with Buchnera aphidicola, which provides essential amino acids to its host and contributes directly to nymph growth and reproduction. We previously found that newly adult Aphis glycines feeding on soybean infected with the beetle-transmitted Bean pod mottle virus (BPMV) had significantly reduced fecundity. We hypothesized that the reduced fecundity was attributable to detrimental impacts of the virus on the aphid microbiome, namely Buchnera. To test this, mRNA sequencing and quantitative real-time PCR were used to assay Buchnera transcript abundance and titre in A. glycines feeding on Soybean mosaic virus-infected, BPMV-infected, and healthy soybean for up to 14 days. Our results indicated that Buchnera density was lower and ultimately suppressed in aphids feeding on virus-infected soybean. While the decreased Buchnera titre may be associated with reduced aphid fecundity, additional mechanisms are probably involved. The present report begins to describe how interactions among insects, plants, and plant pathogens influence endosymbiont population dynamics.
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Affiliation(s)
- Bryan J Cassone
- Center for Applied Plant Sciences, The Ohio State University, OARDC, Wooster, OH, 44691, USA
- Department of Plant Pathology, The Ohio State University, OARDC, Wooster, OH, 44691, USA
| | - Margaret G Redinbaugh
- Department of Plant Pathology, The Ohio State University, OARDC, Wooster, OH, 44691, USA
- USDA, ARS Corn, Soybean and Wheat Quality Research Unit, Wooster, OH, 44691, USA
| | - Anne E Dorrance
- Department of Plant Pathology, The Ohio State University, OARDC, Wooster, OH, 44691, USA
| | - Andrew P Michel
- Department of Entomology, the Ohio State University, OARDC, Wooster, OH, 44691, USA
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6
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Dossi FCA, da Silva EP, Cônsoli FL. Population dynamics and growth rates of endosymbionts during Diaphorina citri (Hemiptera, Liviidae) ontogeny. MICROBIAL ECOLOGY 2014; 68:881-9. [PMID: 25037159 DOI: 10.1007/s00248-014-0463-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 07/04/2014] [Indexed: 05/26/2023]
Abstract
The infection density of symbionts is among the major parameters to understand their biological effects in host-endosymbionts interactions. Diaphorina citri harbors two bacteriome-associated bacterial endosymbionts (Candidatus Carsonella ruddii and Candidatus Profftella armatura), besides the intracellular reproductive parasite Wolbachia. In this study, the density dynamics of the three endosymbionts associated with the psyllid D. citri was investigated by real-time quantitative PCR (qPCR) at different developmental stages. Bacterial density was estimated by assessing the copy number of the 16S rRNA gene for Carsonella and Profftella, and of the ftsZ gene for Wolbachia. Analysis revealed a continuous growth of the symbionts during host development. Symbiont growth and rate curves were estimated by the Gompertz equation, which indicated a negative correlation between the degree of symbiont-host specialization and the time to achieve the maximum growth rate (t*). Carsonella densities were significantly lower than those of Profftella at all host developmental stages analyzed, even though they both displayed a similar trend. The growth rates of Wolbachia were similar to those of Carsonella, but Wolbachia was not as abundant. Adult males displayed higher symbiont densities than females. However, females showed a much more pronounced increase in symbiont density as they aged if compared to males, regardless of the incorporation of symbionts into female oocytes and egg laying. The increased density of endosymbionts in aged adults differs from the usual decrease observed during host aging in other insect-symbiont systems.
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Affiliation(s)
- Fabio Cleisto Alda Dossi
- Insect Interactions Laboratory, Department of Entomology and Acarology, College of Agriculture "Luiz de Queiroz", University of São Paulo, Piracicaba, São Paulo, Brazil,
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Genomic revelations of a mutualism: the pea aphid and its obligate bacterial symbiont. Cell Mol Life Sci 2011; 68:1297-309. [PMID: 21390549 PMCID: PMC3064905 DOI: 10.1007/s00018-011-0645-2] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 02/15/2011] [Accepted: 02/15/2011] [Indexed: 11/22/2022]
Abstract
The symbiosis of the pea aphid Acyrthosphion pisum with the bacterium Buchnera aphidicola APS represents the best-studied insect obligate symbiosis. Here we present a refined picture of this symbiosis by linking pre-genomic observations to new genomic data that includes the complete genomes of the eukaryotic and prokaryotic symbiotic partners. In doing so, we address four issues central to understanding the patterns and processes operating at the A. pisum/Buchnera APS interface. These four issues include: (1) lateral gene transfer, (2) host immunity, (3) symbiotic metabolism, and (4) regulation.
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8
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Humphreys NJ, Douglas AE. Partitioning of Symbiotic Bacteria between Generations of an Insect: a Quantitative Study of a Buchnera sp. in the Pea Aphid (Acyrthosiphon pisum) Reared at Different Temperatures. Appl Environ Microbiol 2010; 63:3294-6. [PMID: 16535678 PMCID: PMC1389233 DOI: 10.1128/aem.63.8.3294-3296.1997] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The population of symbiotic Buchnera bacteria in parthenogenetic females of the pea aphid Acyrthosiphon pisum was determined by quantitative hybridization of a DNA probe (groESL) to aphid homogenates. The aphids bore 1 x 10(sup7) to 2 x 10(sup7) bacterial cells per mg (fresh weight). In teneral aphids (i.e., aphids that had moulted to adulthood but that had not initiated reproduction), >75% of the bacteria were in the embryos, and the density of bacteria in the embryos was consistently greater than that in the maternal tissues. The bacterial density in teneral aphids increased from 1.3 x 10(sup7) to 2.0 x 10(sup7) cells mg (fresh weight) of aphids(sup-1) with temperature between 15 and 25(deg)C. This variation could be attributed to a temperature-dependent increase in both the density of bacteria in the embryos and embryo content of the aphids.
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9
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Gil R, Latorre A, Moya A. Evolution of Prokaryote-Animal Symbiosis from a Genomics Perspective. (ENDO)SYMBIOTIC METHANOGENIC ARCHAEA 2010. [DOI: 10.1007/978-3-642-13615-3_11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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10
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Chen CY, Lai CY, Kuo MH. Temperature effect on the growth of Buchnera endosymbiont in Aphis craccivora (Hemiptera: Aphididae). Symbiosis 2009. [DOI: 10.1007/s13199-009-0011-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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11
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Jousselin E, Desdevises Y, Coeur d'acier A. Fine-scale cospeciation between Brachycaudus and Buchnera aphidicola: bacterial genome helps define species and evolutionary relationships in aphids. Proc Biol Sci 2009; 276:187-96. [PMID: 18782748 DOI: 10.1098/rspb.2008.0679] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Aphids harbour an obligatory symbiont, Buchnera aphidicola, providing essential amino acids not supplied by their diet. These bacteria are transmitted vertically and phylogenic analyses suggest that they have 'cospeciated' with their hosts. We investigated this cospeciation phenomenon at a fine taxonomic level, within the aphid genus Brachycaudus. We used DNA-based methods of species delimitation in both organisms, to avoid biases in the definition of aphid and Buchnera species and to infer association patterns without the presumption of a specific interaction. Our results call into question certain 'taxonomic' species of Brachycaudus and suggest that B. aphidicola has diversified into independently evolving entities, each specific to a 'phylogenetic' Brachycaudus species. We also found that Buchnera and their hosts simultaneously diversified, in parallel. These results validate the use of Buchnera DNA data for inferring the evolutionary history of their host. The Buchnera genome evolves rapidly, making it the perfect tool for resolving ambiguities in aphid taxonomy. This study also highlights the usefulness of species delimitation methods in cospeciation studies involving species difficult to conceptualize--as is the case for bacteria--and in cases in which the taxonomy of the interacting organisms has not been determined independently and species definition depends on host association.
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Affiliation(s)
- Emmanuelle Jousselin
- INRA, UMR CBGP (INRA/IRD/Cirad/Montpellier SupAgro), Campus International de Baillarguet, CS 30016, 34988 Montferrier-sur-Lez cedex, France.
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12
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Wilkinson TL, Koga R, Fukatsu T. Role of host nutrition in symbiont regulation: impact of dietary nitrogen on proliferation of obligate and facultative bacterial endosymbionts of the pea aphid Acyrthosiphon pisum. Appl Environ Microbiol 2007; 73:1362-6. [PMID: 17158610 PMCID: PMC1828675 DOI: 10.1128/aem.01211-06] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Accepted: 12/03/2006] [Indexed: 11/20/2022] Open
Abstract
The impact of host nutrition on symbiont regulation in the pea aphid Acyrthosiphon pisum was investigated. The population density of the obligate symbiont Buchnera aphidicola positively correlated with dietary nitrogen levels. In contrast, the population density of the facultative symbiont Serratia symbiotica increased in aphids reared on low-nitrogen diets, indicating distinct regulatory mechanisms in the same insect host.
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Affiliation(s)
- T L Wilkinson
- UCD School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland.
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13
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Abstract
Symbiotic bacteria are important in animal hosts, but have been largely overlooked as they have proved difficult to culture in the laboratory. Approaches such as comparative genomics and real-time PCR have provided insights into the molecular mechanisms that underpin symbiont-host interactions. Studies on the heritable symbionts of insects have yielded valuable information about how bacteria infect host cells, avoid immune responses, and manipulate host physiology. Furthermore, some symbionts use many of the same mechanisms as pathogens to infect hosts and evade immune responses. Here we discuss what is currently known about the interactions between bacterial symbionts and their hosts.
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Affiliation(s)
- Colin Dale
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
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14
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Abstract
In many animal groups, mutualistic bacterial symbionts play a central role in host ecology, by provisioning rare nutrients and thus enabling specialization on restricted diets. Among such symbionts, genomic studies are most advanced for Buchnera, the obligate symbiont of aphids, which feed on phloem sap. The contents of the highly reduced Buchnera genomes have verified its role in aphid nutrition. Comparisons of Buchnera gene sets indicate ongoing, irreversible gene losses that are expected to affect aphid nutritional needs. Furthermore, almost all regulatory genes have been eliminated, raising the question of whether and how gene expression responds to environmental change. Microarray studies on genome-wide expression indicate that Buchnera has evolved some constitutive changes in gene expression: homologues of heat stress genes have elevated transcript levels in Buchnera (relative to other bacteria) even in the absence of stress. Additionally, the microarray results indicate that responses to heat stress and to amino acid availability are both few and modest. Observed responses are consistent with control by the few ancestral regulators retained in the genome. Initial studies on the role of host genes in mediating the symbiosis reveal distinctive expression patterns in host cells harbouring Buchnera. In the near future, a complete genome of pea aphid will accelerate progress in understanding the functional integration of aphid and Buchnera genomes. Although information for other insect symbioses is relatively limited, studies on symbionts of carpenter ants and tsetse flies indicate many similarities to Buchnera.
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Affiliation(s)
- Nancy A Moran
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA.
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15
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Fry AJ, Wernegreen JJ. The roles of positive and negative selection in the molecular evolution of insect endosymbionts. Gene 2005; 355:1-10. [PMID: 16039807 DOI: 10.1016/j.gene.2005.05.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Revised: 03/29/2005] [Accepted: 05/17/2005] [Indexed: 11/19/2022]
Abstract
The evolutionary rate acceleration observed in most endosymbiotic bacteria may be explained by higher mutation rates, changes in selective pressure, and increased fixation of deleterious mutations by genetic drift. Here, we explore the forces influencing molecular evolution in Blochmannia, an obligate endosymbiont of Camponotus and related ant genera. Our goals were to compare rates of sequence evolution in Blochmannia with related bacteria, to explore variation in the strength and efficacy of negative (purifying) selection, and to evaluate the effect of positive selection. For six Blochmannia pairs, plus Buchnera and related enterobacteria, estimates of sequence divergence at four genes confirm faster rates of synonymous evolution in the ant mutualist. This conclusion is based on higher dS between Blochmannia lineages despite their more recent divergence. Likewise, generally higher dN in Blochmannia indicates faster rates of nonsynonymous substitution in this group. One exception is the groEL gene, for which lower dN and dN/dS compared to Buchnera indicate exceptionally strong negative selection in Blochmannia. In addition, we explored evidence for positive selection in Blochmannia using both site-and lineage-based maximum likelihood models. These approaches confirmed heterogeneity of dN/dS among codon sites and revealed significant variation in dN/dS across Blochmannia lineages for three genes. Lineage variation affected genes independently, with no evidence of parallel changes in dN/dS across genes along a given branch. Our data also reveal instances of dN/dS greater than one; however, we do not interpret these large dN/dS ratios as evidence for positive selection. In sum, while drift may contribute to an overall rate acceleration at nonsynonymous sites in Blochmannia, variable selective pressures best explain the apparent gene-specific changes in dN/dS across lineages of this ant mutualist. In the course of this study, we reanalyzed variation at Buchnera groEL and found no evidence of positive selection that was previously reported.
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Affiliation(s)
- Adam J Fry
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA
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16
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Abstract
The development of molecular techniques for the study of uncultured bacteria allowed the extensive study of the widespread association between insects and intracellular symbiotic bacteria. Most of the bacterial endosymbionts involved in such associations are gamma-proteobacteria, closely related to Escherichia coli. In recent years, five genomes from insect endosymbionts have been sequenced, allowing the performance of extensive genome comparative analysis that, as a complement of phylogenetic studies, and analysis on individual genes, can help to understand the different traits of this particular association, including how the symbiotic process is established, the explanation of the special features of these microbial genomes, the bases of this intimate association and the possible future that awaits the endosymbionts with extremely reduced genomes.
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Affiliation(s)
- Rosario Gil
- Institut Cavanilles de Biodiversitat i Biologia Evolutiva and Departament de Genètica, Universitat de València, Apartado Postal 22085, 46071 Valencia, Spain.
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17
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Wolschin F, Hölldobler B, Gross R, Zientz E. Replication of the endosymbiotic bacterium Blochmannia floridanus is correlated with the developmental and reproductive stages of its ant host. Appl Environ Microbiol 2004; 70:4096-102. [PMID: 15240288 PMCID: PMC444795 DOI: 10.1128/aem.70.7.4096-4102.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The dynamics of replication of the intracellular endosymbiotic bacterium Blochmannia floridanus was determined during the larval development of its host ant Camponotus floridanus by real-time quantitative PCR. The bacteria were found to proliferate during pupation and immediately after the eclosion of the imagines (adult ants). In older workers the number of bacteria present in the midgut bacteriocytes decreased significantly. In contrast, the bacterial population in the ovaries was dependent on the reproductive state of the animal. An age-dependent degeneration of the midgut bacteriocytes was also investigated by microscopic techniques in males and female castes of the closely related ant species C. herculeanus and C. sericeiventris, respectively, with similar results and supports the concept of age-dependent degeneration of the midgut bacteriocytes in all castes.
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Affiliation(s)
- Florian Wolschin
- Lehrstuhl für Mikrobiologie, Biozentrum, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.
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18
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Bianciotto V, Genre A, Jargeat P, Lumini E, Bécard G, Bonfante P. Vertical transmission of endobacteria in the arbuscular mycorrhizal fungus Gigaspora margarita through generation of vegetative spores. Appl Environ Microbiol 2004; 70:3600-8. [PMID: 15184163 PMCID: PMC427789 DOI: 10.1128/aem.70.6.3600-3608.2004] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Accepted: 03/03/2004] [Indexed: 12/31/2022] Open
Abstract
Arbuscular mycorrhizal (AM) fungi living in symbiotic association with the roots of vascular plants have also been shown to host endocellular rod-shaped bacteria. Based on their ribosomal sequences, these endobacteria have recently been identified as a new taxon, Candidatus Glomeribacter gigasporarum. In order to investigate the cytoplasmic stability of the endobacteria in their fungal host and their transmission during AM fungal reproduction (asexual), a system based on transformed carrot roots and single-spore inocula of Gigaspora margarita was used. Under these in vitro sterile conditions, with no risk of horizontal contamination, the propagation of endobacteria could be monitored, and it was shown, by using primers designed for both 16S and 23S ribosomal DNAs, to occur through several vegetative spore generations (SG0 to SG4). A method of confocal microscopy for quantifying the density of endobacteria in spore cytoplasm was designed and applied; endobacteria were consistently found in all of the spore generations, although their number rapidly decreased from SG0 to SG4. The study demonstrates that a vertical transmission of endobacteria takes place through the fungal vegetative generations (sporulation) of an AM fungus, indicating that active bacterial proliferation occurs in the coenocytic mycelium of the fungus, and suggests that these bacteria are obligate endocellular components of their AM fungal host.
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Affiliation(s)
- V Bianciotto
- Dipartimento di Biologia Vegetale dell'Università e Istituto per la Protezione delle Piante CNR, 10125 Turin, Italy
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Rispe C, Delmotte F, van Ham RCHJ, Moya A. Mutational and selective pressures on codon and amino acid usage in Buchnera, endosymbiotic bacteria of aphids. Genome Res 2004; 14:44-53. [PMID: 14672975 PMCID: PMC314276 DOI: 10.1101/gr.1358104] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have explored compositional variation at synonymous (codon usage) and nonsynonymous (amino acid usage) positions in three complete genomes of Buchnera, endosymbiotic bacteria of aphids, and also in their orthologs in Escherichia coli, a close free-living relative. We sought to discriminate genes of variable expression levels in order to weigh the relative contributions of mutational bias and selection in the genomic changes following symbiosis. We identified clear strand asymmetries, distribution biases (putative high-expression genes were found more often on the leading strand), and a residual slight codon bias within each strand. Amino acid usage was strongly biased in putative high-expression genes, characterized by avoidance of aromatic amino acids, but above all by greater conservation and resistance to AT enrichment. Despite the almost complete loss of codon bias and heavy mutational pressure, selective forces are still strong at nonsynonymous sites of a fraction of the genome. However, Buchnera from Baizongia pistaciae appears to have suffered a stronger symbiotic syndrome than the two other species.
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Affiliation(s)
- Claude Rispe
- UMR BIO3P, Institut National de la Recherche Agronomique, BP35327, 35653 Le Rheu cedex, France.
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Anbutsu H, Fukatsu T. Population dynamics of male-killing and non-male-killing spiroplasmas in Drosophila melanogaster. Appl Environ Microbiol 2003; 69:1428-34. [PMID: 12620825 PMCID: PMC150097 DOI: 10.1128/aem.69.3.1428-1434.2003] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The endosymbiotic bacteria Spiroplasma spp. are vertically transmitted through female hosts and are known to cause selective death of male offspring in insects. One strain of spiroplasma, NSRO, causes male killing in Drosophila species, and a non-male-killing variant of NSRO, designated NSRO-A, has been isolated. It is not known why NSRO-A does not kill males. In an attempt to understand the mechanism of male killing, we investigated the population dynamics of NSRO and NSRO-A throughout the developmental course of the laboratory host Drosophila melanogaster by using a quantitative PCR technique. In the early development of the host insect, the titers of NSRO were significantly higher than those of NSRO-A at the first- and second-instar stages, whereas at the egg, third-instar, and pupal stages, the titers of the two spiroplasmas were almost the same. Upon adult emergence, the titers of the two spiroplasmas were similar, around 2 x 10(8) dnaA copy equivalents. However, throughout host aging, the two spiroplasmas showed strikingly different population growth patterns. The titers of NSRO increased exponentially for 3 weeks, attained a peak value of around 4 x 10(9) dnaA copy equivalents per insect, and then decreased. In contrast, the titers of NSRO-A were almost constant throughout the adult portion of the life cycle. In adult females, consequently, the titer of NSRO was significantly higher than the titer of NSRO-A except for a short period just after emergence. Although infection of adult females with NSRO resulted in almost 100% male killing, production of some male offspring was observed within 4 days after emergence when the titers of NSRO were as low as those of NSRO-A. Based on these results, we proposed a threshold density hypothesis for the expression of male killing caused by the spiroplasma. The extents of the bottleneck in the vertical transmission through host generations were estimated to be 5 x 10(-5) for NSRO and 3 x 10(-4) for NSRO-A.
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Affiliation(s)
- Hisashi Anbutsu
- Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 6, Tsukuba, Ibaraki 305-8566, Japan
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Wilkinson TL, Adams D, Minto LB, Douglas AE. The impact of host plant on the abundance and function of symbiotic bacteria in an aphid. J Exp Biol 2001; 204:3027-38. [PMID: 11551991 DOI: 10.1242/jeb.204.17.3027] [Citation(s) in RCA: 43] [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
SUMMARY
The black-bean aphid Aphis fabae bears populations of coccoid symbiotic bacteria Buchnera spp. at 2.0–3.2×107cellsmg−1aphidmass and rod-shaped secondary symbionts of uncertain taxonomic affiliation at 0.1–0.6×107cellsmg−1aphidmass. Buchnera provides essential amino acids, supplementing the poor supply in the aphid diet of plant phloem sap. Comparison of the performance of A. fabae containing and experimentally deprived of their bacteria showed that the bacteria caused increased larval mass of aphids reared on Chenopodium album and Papaver dubium plants, but not when reared on Lamium purpureum. In the aphids reared on L. purpureum, the density of the bacteria, especially the secondary symbionts, was significantly elevated, and bacterial-mediated production of the essential amino acid threonine was reduced, even though the essential amino acid content of phloem exudates from L. purpureum had a low threonine content. It is proposed that the shortfall in threonine, possibly compounded by the high density of secondary symbionts, may contribute to the poor performance of the aphids on L. purpureum. This study offers the first evidence to suggest plant-mediated interference with the nutritional function of symbiotic bacteria in any phytophagous insect.
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Affiliation(s)
- T L Wilkinson
- Department of Biology, University of York, York, YO10 5YW, UK.
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de Vries EJ, Jacobs G, Breeuwer JA. Growth and transmission of gut bacteria in the Western flower thrips, Frankliniella occidentalis. J Invertebr Pathol 2001; 77:129-37. [PMID: 11273693 DOI: 10.1006/jipa.2001.5010] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Western flower thrips (Frankliniella occidentalis), a polyphagous insect with global distribution, has a permanent association with a near Erwinia species TAC bacterium in its hindgut. Since this bacterium is able to grow outside the thrips, it is a facultative symbiont that is not completely dependent on the host. In this study we address the question of how the association is maintained and how bacteria are transmitted to newly hatched thrips larvae. Bacteria are passed on to new thrips via the food source. No evidence was found for vertical transmission from mother to offspring via the egg. Gut bacteria show unlimited growth during the larval (feeding) stages, and in the second instar stage 100% of the larvae become infected with high numbers of bacteria. In the prepupal and pupal stage, the number of bacteria declines, but increases again during the adult phase. A method to rear aposymbiotic (bacteria-free) thrips is described which enables studies on the impact of bacteria on the fitness of thrips.
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Affiliation(s)
- E J de Vries
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Kruislaan 320, Amsterdam, 1098 SM, The Netherlands.
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Rispe C, Moran NA. Accumulation of Deleterious Mutations in Endosymbionts: Muller’s Ratchet with Two Levels of Selection. Am Nat 2000; 156:425-441. [DOI: 10.1086/303396] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Abstract
Attempts to calibrate bacterial evolution have relied on the assumption that rates of molecular sequence divergence in bacteria are similar to those of higher eukaryotes, or to those of the few bacterial taxa for which ancestors can be reliably dated from ecological or geological evidence. Despite similarities in the substitution rates estimated for some lineages, comparisons of the relative rates of evolution at different classes of nucleotide sites indicate no basis for their universal application to all bacteria. However, there is evidence that bacteria have a constant genome-wide mutation rate on an evolutionary time scale but that this rate differs dramatically from the rate estimated by experimental methods.
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Affiliation(s)
- H Ochman
- Department of Ecology, University of Arizona, Tucson, AZ 85721, USA.
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Martínez-Torres D, Moya A, Latorre A. Plasmid-encoded anthranilate synthase (TrpEG) in Buchnera aphidicola from aphids of the family pemphigidae. Appl Environ Microbiol 1999; 65:117-25. [PMID: 9872768 PMCID: PMC90991 DOI: 10.1128/aem.65.1.117-125.1999] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Buchnera aphidicola is an obligate intracellular symbiont of aphids. One of its proposed functions is the synthesis of essential amino acids, nutrients required by aphids but deficient in their diet of plant phloem sap. The genetic organization of the tryptophan pathway in Buchnera from proliferous aphids of the family Aphididae has previously been shown to reflect a capacity to overproduce this essential amino acid (C.-Y. Lai, L. Baumann, and P. Baumann, Proc. Natl. Acad. Sci. USA 91:3819-3823, 1994). This involved amplification of the genes for the first enzyme in the pathway, anthranilate synthase (TrpEG), on a low-copy-number plasmid. Here we report on the finding and molecular characterization of TrpEG-encoding plasmids in Buchnera from aphids of the distantly related family Pemphigidae. Buchnera from Tetraneura caerulescens contained a 3.0-kb plasmid (pBTc2) that carried a single copy of trpEG and resembled trpEG plasmids of Buchnera from the Aphididae. The second plasmid (pBPs2), isolated from Buchnera of Pemphigus spyrothecae, contained a different replicon. It consisted of a putative origin of replication containing iterons and an open reading frame, designated repAC, which showed a high similarity to the gene encoding the replication initiation protein RepA of the RepA/C replicon from the broad-host-range IncA/C group of plasmids. The plasmid population was heterogeneous with respect to the number of tandem repeats of a 1.8-kb unit carrying repAC1, trpG, and remnants of trpE. The two principal forms consisted of either five or six copies of this repeat and a single-copy region carrying repAC2, the putative origin of replication, and trpE. The unexpected finding of elements of the RepA/C replicon in previously characterized trpEG plasmids from Buchnera of the Aphididae suggests that a replacement of replicons has occurred during the evolution of these plasmids, which may point to a common ancestry for all Buchnera trpEG amplifications.
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Douglas AE, Wilkinson TL. Host cell allometry and regulation of the symbiosis between pea aphids, Acyrthosiphon pisum, and bacteria, Buchnera. JOURNAL OF INSECT PHYSIOLOGY 1998; 44:629-635. [PMID: 12769945 DOI: 10.1016/s0022-1910(98)00030-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The symbiotic bacteria Buchnera in aphids are borne in cells, called bacteriocytes, in the insect haemocoel. The number and median volume of bacteriocytes in pre-reproductive adult insects varied significantly among 14 parthenogenetic clones of the pea aphid Acyrthosiphon pisum. After logarithmic transformation of the data, the relationship of both number and median volume of bacteriocytes with aphid weight for the clones could be described by common regression lines with slopes significantly greater than zero. The allometric slope for median bacteriocyte volume was calculated as 1.06, by model I regression and 1.94 by model II regression; and the equivalent values of the allometric slope for total volume of bacteriocytes were 1.51 and 2.50, suggesting that the total volume of bacteriocytes increases disproportionately with aphid body weight. The partial correlation coefficient between the number and median volume of bacteriocytes was +0.07, with body weight held constant. It is proposed that the regulation of number and size of bacteriocytes is not linked and that bacteriocytes may not exhibit compensatory changes in size, in response to alteration in number. Experimental manipulation of the rates of bacteriocyte differentiation and division could therefore perturb the total volume of the symbiosis, on which aphid pests depend for normal growth and reproduction.
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Affiliation(s)
- A E. Douglas
- Department of Biology, University of York, PO Box 373, York, UK
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Wilkinson T. The elimination of intracellular microorganisms from insects: an analysis of antibiotic-treatment in the pea aphid (Acyrthosiphon pisum). Comp Biochem Physiol A Mol Integr Physiol 1998. [DOI: 10.1016/s1095-6433(98)00013-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Douglas AE. Nutritional interactions in insect-microbial symbioses: aphids and their symbiotic bacteria Buchnera. ANNUAL REVIEW OF ENTOMOLOGY 1998; 43:17-37. [PMID: 15012383 DOI: 10.1146/annurev.ento.43.1.17] [Citation(s) in RCA: 795] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Most aphids possess intracellular bacteria of the genus Buchnera. The bacteria are transmitted vertically via the aphid ovary, and the association is obligate for both partners: Bacteria-free aphids grow poorly and produce few or no offspring, and Buchnera are both unknown apart from aphids and apparently unculturable. The symbiosis has a nutritional basis. Specifically, bacterial provisioning of essential amino acids has been demonstrated. Nitrogen recycling, however, is not quantitatively important to the nutrition of aphid species studied, and there is strong evidence against bacterial involvement in the lipid and sterol nutrition of aphids. Buchnera have been implicated in various non-nutritional functions. Of these, just one has strong experimental support: promotion of aphid transmission of circulative viruses. It is argued that strong parallels may exist between the nutritional interactions (including the underlying mechanisms) in the aphid-Buchnera association and other insect symbioses with intracellular microorganisms.
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Affiliation(s)
- A E Douglas
- Department of Biology, University of York, PO Box 373, York, YO1 5YW, UK.
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Rouhbakhsh D, Clark MA, Baumann L, Moran NA, Baumann P. Evolution of the tryptophan biosynthetic pathway in Buchnera (aphid endosymbionts): studies of plasmid-associated trpEG within the genus Uroleucon. Mol Phylogenet Evol 1997; 8:167-76. [PMID: 9299222 DOI: 10.1006/mpev.1997.0419] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Aphids obtain tryptophan from prokaryotic endosymbionts assigned to the genus Buchnera. The rate-limiting enzyme in tryptophan biosynthes, anthranilate synthase, is encoded by the genes trpE and trpG. In Buchnera within the family Aphididae, trpEG is plasmid-borne, apparently as an adaptation to overproduce tryptophan for hosts. To explore the evolution of these plasmids, sequences for trpEG, the upstream region containing the plasmid origin of replication, and chromosomal trpB were obtained for Buchnera of three species in the aphid genus Uroleucon and analyzed together with sequences for six other aphid species. Phylogenies based on trpB and trpEG agree with each other and with previous views of aphid phylogeny. Synonymous substitutions are about twice as high for plasmid-borne genes as for chromosomal genes in the same lineages, suggesting higher mutation rates for genes on plasmids. Nonsynonymous rates for trpEG are accelerated within Buchnera of Uroleucon, indicating a change in selection intensity within this genus. Accelerated evolution within Uroleucon also seems to characterize the upstream region containing the putative origin of replication.
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Affiliation(s)
- D Rouhbakhsh
- Microbiology Section, University of California, Davis, California, 95616-8665, USA
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van Ham RC, Moya A, Latorre A. Putative evolutionary origin of plasmids carrying the genes involved in leucine biosynthesis in Buchnera aphidicola (endosymbiont of aphids). J Bacteriol 1997; 179:4768-77. [PMID: 9244264 PMCID: PMC179323 DOI: 10.1128/jb.179.15.4768-4777.1997] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
An 8.5-kb plasmid encoding genes (leuABCD) involved in leucine biosynthesis and a small plasmid of 1.74 kb of yet unknown function were found in the intracellular symbiont, Buchnera aphidicola, of two divergent aphid species, Thelaxes suberi and Tetraneura caerulescens, respectively. The leuABCD-carrying plasmid (pBTs1) was amplified from total aphid DNA by inverse long PCR, using outwardly oriented oligonucleotide primers specific to leuA. The resulting 8.2-kb PCR fragment as well as the 1.74-kb plasmid (pBTc1) were cloned and sequenced. pBTs1 differed from a previously described B. aphidicola plasmid (pRPE) of the aphid Rhopalosiphum padi by the presence of a small heat shock gene (ibp) and in the order of the leuABCD and repA genes. Comparison of both leucine plasmids to the small plasmid pBTc1 revealed extensive similarity with respect to putative replication functions as well as in the presence of a highly conserved open reading frame that was found to be homologous to Escherichia coli YqhA and Haemophilus influenzae HI0507 and which may encode an integral membrane protein. The three B. aphidicola plasmids most likely evolved from a common ancestral replicon, which in turn may be distantly related to IncFII plasmids. Phylogenetic affiliations of the B. aphidicola strains of the two aphid species were assessed by sequencing of their 16S rRNA genes. Evaluation of the distribution of the leuABCD-encoding plasmids within a phylogenetic framework suggests independent origins for pBTs1 and pRPE from an ancestral replicon resembling pBTc1. The implications for symbiotic essential amino acid biosynthesis and provisioning are discussed.
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Affiliation(s)
- R C van Ham
- Department of Genetics, University of Valencia, Spain
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Baumann P, Moran NA, Baumann L. The Evolution and Genetics of Aphid Endosymbionts. Bioscience 1997. [DOI: 10.2307/1313002] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Rouhbakhsh D, Lai CY, von Dohlen CD, Clark MA, Baumann L, Baumann P, Moran NA, Voegtlin DJ. The tryptophan biosynthetic pathway of aphid endosymbionts (Buchnera): genetics and evolution of plasmid-associated anthranilate synthase (trpEG) within the aphididae. J Mol Evol 1996; 42:414-21. [PMID: 8642610 DOI: 10.1007/bf02498635] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The bacterial endosymbionts (Buchnera) from the aphids Rhopalosiphum padi, R. maidis, Schizaphis graminum, and Acyrthosiphon pisum contain the genes for anthranilate synthase (trpEG) on plasmids made up of one or more 3.6-kb units. Anthranilate synthase is the first as well as the rate-limiting enzyme in the tryptophan biosynthetic pathway. The amplification of trpEG on plasmids may result in an increase of enzyme protein and overproduction of this essential amino acid, which is required by the aphid host. The nucleotide sequence of trpEG from endosymbionts of different species of aphids is highly conserved, as is an approximately 500-bp upstream DNA segment which has the characteristics of an origin of replication. Phylogenetic analyses were performed using trpE and trpG from the endosymbionts of these four aphids as well as from the endosymbiont of Schlechtendalia chinensis, in which trpEG occurs on the chromosome. The resulting phylogeny was congruent with trees derived from sequences of two chromosome-located bacterial genes (part of trpB and 16S ribosomal DNA). In turn, trees obtained from plasmid-borne and bacterial chromosome-borne sequences were congruent with the tree resulting from phylogenetic analysis of three aphid mitochondrial regions (portions of the small and large ribosomal DNA subunits, as well as cytochrome oxidase II). Congruence of trees based on genes from host mitochondria and from bacteria adds to previous support for exclusively vertical transmission of the endosymbionts within aphid lineages. Congruence with trees based on plasmid-borne genes supports the origin of the plasmid-borne trpEG from the chromosomal genes of the same lineage and the absence of subsequent plasmid exchange among endosymbionts of different species of aphids.
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Affiliation(s)
- D Rouhbakhsh
- Microbiology Section, University of California, Davis 95616-8665, USA
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Lai CY, Baumann P, Moran N. The endosymbiont (Buchnera sp.) of the aphid Diuraphis noxia contains plasmids consisting of trpEG and tandem repeats of trpEG pseudogenes. Appl Environ Microbiol 1996; 62:332-9. [PMID: 8593038 PMCID: PMC167803 DOI: 10.1128/aem.62.2.332-339.1996] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Most aphids are dependent for their survival on prokaryotic endosymbionts assigned to the genus Buchnera. Among the functions of Buchnera species is the synthesis of tryptophan, which is required by the aphid host. In Buchnera species from the aphid Diuraphis noxia, the genes for anthranilate synthase (trpEG) were found on a plasmid which consisted of seven tandem repeats of a 3.2-kb unit and one 2.6-kb unit which differed in containing a 0.6-kb deletion. One of the 3.2-kb units contained open reading frames corresponding to trpEG; the remaining units contained trpEG pseudogenes (psi). The nucleotide sequence upstream of trpE contained a region that has characteristics of an origin of replication (ori). Relative to trpB (a chromosomal gene), there were about two copies of the trpEG-containing plasmid. Comparisons of the nucleotide sequences of the 3.2-kb units containing trpEG and psi trpEG indicated that most changes occurred in a 700-nucleotide segment that included the region upstream of trpE and the portion of this gene coding for the N terminus. The consequence of these changes was the silencing of trpEG by inactivation of the putative promoter region and premature termination of the TrpE peptide. In contrast, the nucleotide sequence of the segment corresponding to ori was conserved in the units containing trpEG and psi trpEG. We offer a number of speculations on the evolutionary pressure in this lineage which resulted in the silencing of most of trpEG while still retaining the regions resembling ori.
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Affiliation(s)
- C Y Lai
- Microbiology Section, University of California, Davis, 95616-8665, USA
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Rouhbakhsh D, Baumann P. Characterization of a putative 23S-5S rRNA operon of Buchnera aphidicola (endosymbiont of aphids) unlinked to the 16S rRNA-encoding gene. Gene 1995; 155:107-12. [PMID: 7535281 DOI: 10.1016/0378-1119(94)00910-k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Buchnera aphidicola (Ba) is an endosymbiont of the aphid Schizaphis graminum. In order to obtain information on highly expressed genes, we have chosen to study Ba genes coding for rRNAs. Previously, the single-copy rrs gene was cloned and sequenced [Munson et al., Gene 137 (1993) 171-178], and found to constitute a single transcription unit unlinked to rrl and rrf. In the present study, a 6.1-kb Ba DNA fragment containing rrl was cloned into Escherichia coli (Ec) and sequenced. Based on sequence similarity to Ec, the following genes were identified: aroE-tRNA(Glu)-rrl-rrf-cysS. AroE and CysS had 48 and 54% amino acid (aa) identity, respectively, to the corresponding Ec proteins; tRNA(Glu), rrl and rrf had 80-90% nucleotide (nt) identity with the corresponding genes of Ec rrnB. Ba tRNA(Glu)-rrl-rrs appears to be part of a single transcriptional unit; a putative promoter and a Rho-independent terminator were identified. Comparisons of sequences of aroE-rrl from endosymbionts of seven additional species of aphids indicated conservation of the -35 (TTGACT) and -10 (TGTAA/TT) promoter regions, and boxA, tRNA(Glu) and boxC. Secondary structure analysis indicated that the Ba tRNA(Glu)-rrl-rrf operon resembled the homologous region of Ec rrnB. The results of this and previous studies indicate that Ba differs from most bacteria in having the single-copy rRNA genes organized into two transcription units.
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Affiliation(s)
- D Rouhbakhsh
- Microbiology Section, University of California, Davis 95616-8665, USA
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Lai CY, Baumann P, Moran NA. Genetics of the tryptophan biosynthetic pathway of the prokaryotic endosymbiont (Buchnera) of the aphid Schlechtendalia chinensis. INSECT MOLECULAR BIOLOGY 1995; 4:47-59. [PMID: 7742976 DOI: 10.1111/j.1365-2583.1995.tb00007.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Two DNA fragments (3941 and 7152 base pairs) from the procaryotic endosymbiont (Buchnera) of the aphid Schlechtendalia chinensis were cloned and sequenced. The smaller fragment contained trpEG and the larger fragment contained trpDC(F)BA, genes coding for enzymes of the tryptophan biosynthetic pathway which convert chorismate to tryptophan. Both of these gene clusters were present as one copy on the endosymbiont chromosome and probably constitute two transcription units. The deduced amino acid sequences of the proteins was 51-61% identical to the corresponding proteins were previously studied in Buchnera of the aphid Schizaphis graminum. In this endosymbiont, trpEG is amplified and located on a plasmid, whereas, in the endosymbiont of S. chinensis, as in other eubacteria, trpEG occurs as a single copy on the bacterial chromosome. Implications of these findings for the evolution of this mutualistic association are discussed.
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Affiliation(s)
- C Y Lai
- Microbiology Section, University of California, Davis 95616-8665, USA
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Baumann P, Lai C, Baumann L, Rouhbakhsh D, Moran NA, Clark MA. Mutualistic associations of aphids and prokaryotes: biology of the genus buchnera. Appl Environ Microbiol 1995; 61:1-7. [PMID: 16534896 PMCID: PMC1388313 DOI: 10.1128/aem.61.1.1-7.1995] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Rouhbakhsh D, Moran NA, Baumann L, Voegtlin DJ, Baumann P. Detection of Buchnera, the primary prokaryotic endosymbiont of aphids, using the polymerase chain reaction. INSECT MOLECULAR BIOLOGY 1994; 3:213-217. [PMID: 7535631 DOI: 10.1111/j.1365-2583.1994.tb00169.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Members of the genus Buchnera constitute a distinct prokaryotic lineage containing the primary endosymbionts of aphids (Homoptera: Aphidoidea). Using synthetic oligonucleotides in conjunction with the polymerase chain reaction, we propose three approaches for the identification of members of this genus. The first is based on unique sequences within rrs (gene coding for 16S ribosomal RNA). The second is based on a different and unique organization of the ribosomal RNA operons of Buchnera and the close proximity of aroE upstream of rrl (gene coding for 23S rRNA). The third is based on the linkage relationship of argS which is upstream of rrs. Validation of these three approaches requires their more extensive application.
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Affiliation(s)
- D Rouhbakhsh
- Microbiology Section, University of California, Davis 95616-8665
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