1
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Riley AB, Grillo MA, Epstein B, Tiffin P, Heath KD. Discordant population structure among rhizobium divided genomes and their legume hosts. Mol Ecol 2023; 32:2646-2659. [PMID: 36161739 DOI: 10.1111/mec.16704] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 09/15/2022] [Accepted: 09/20/2022] [Indexed: 11/29/2022]
Abstract
Symbiosis often occurs between partners with distinct life history characteristics and dispersal mechanisms. Many bacterial symbionts have genomes comprising multiple replicons with distinct rates of evolution and horizontal transmission. Such differences might drive differences in population structure between hosts and symbionts and among the elements of the divided genomes of bacterial symbionts. These differences might, in turn, shape the evolution of symbiotic interactions and bacterial evolution. Here we use whole genome resequencing of a hierarchically structured sample of 191 strains of Sinorhizobium meliloti collected from 21 locations in southern Europe to characterize population structures of this bacterial symbiont, which forms a root nodule symbiosis with the host plant Medicago truncatula. S. meliloti genomes showed high local (within-site) variation and little isolation by distance. This was particularly true for the two symbiosis elements, pSymA and pSymB, which have population structures that are similar to each other, but distinct from both the bacterial chromosome and the host plant. Given limited recombination on the chromosome, compared to the symbiosis elements, distinct population structures may result from differences in effective gene flow. Alternatively, positive or purifying selection, with little recombination, may explain distinct geographical patterns at the chromosome. Discordant population structure between hosts and symbionts indicates that geographically and genetically distinct host populations in different parts of the range might interact with genetically similar symbionts, potentially minimizing local specialization.
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Affiliation(s)
- Alex B Riley
- Department of Plant Biology, University of Illinois, Urbana, Illinois, USA
| | - Michael A Grillo
- Department of Biology, Loyola University Chicago, Chicago, Illinois, USA
| | - Brendan Epstein
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Katy D Heath
- Department of Plant Biology, University of Illinois, Urbana, Illinois, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
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2
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Genome-Wide Association Studies across Environmental and Genetic Contexts Reveal Complex Genetic Architecture of Symbiotic Extended Phenotypes. mBio 2022; 13:e0182322. [PMID: 36286519 PMCID: PMC9765617 DOI: 10.1128/mbio.01823-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A goal of modern biology is to develop the genotype-phenotype (G→P) map, a predictive understanding of how genomic information generates trait variation that forms the basis of both natural and managed communities. As microbiome research advances, however, it has become clear that many of these traits are symbiotic extended phenotypes, being governed by genetic variation encoded not only by the host's own genome, but also by the genomes of myriad cryptic symbionts. Building a reliable G→P map therefore requires accounting for the multitude of interacting genes and even genomes involved in symbiosis. Here, we use naturally occurring genetic variation in 191 strains of the model microbial symbiont Sinorhizobium meliloti paired with two genotypes of the host Medicago truncatula in four genome-wide association studies (GWAS) to determine the genomic architecture of a key symbiotic extended phenotype-partner quality, or the fitness benefit conferred to a host by a particular symbiont genotype, within and across environmental contexts and host genotypes. We define three novel categories of loci in rhizobium genomes that must be accounted for if we want to build a reliable G→P map of partner quality; namely, (i) loci whose identities depend on the environment, (ii) those that depend on the host genotype with which rhizobia interact, and (iii) universal loci that are likely important in all or most environments. IMPORTANCE Given the rapid rise of research on how microbiomes can be harnessed to improve host health, understanding the contribution of microbial genetic variation to host phenotypic variation is pressing, and will better enable us to predict the evolution of (and select more precisely for) symbiotic extended phenotypes that impact host health. We uncover extensive context-dependency in both the identity and functions of symbiont loci that control host growth, which makes predicting the genes and pathways important for determining symbiotic outcomes under different conditions more challenging. Despite this context-dependency, we also resolve a core set of universal loci that are likely important in all or most environments, and thus, serve as excellent targets both for genetic engineering and future coevolutionary studies of symbiosis.
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3
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Lau JA, Hammond MD, Schmidt JE, Weese DJ, Yang WH, Heath KD. Contemporary evolution rivals the effects of rhizobium presence on community and ecosystem properties in experimental mesocosms. Oecologia 2022; 200:133-143. [PMID: 36125524 DOI: 10.1007/s00442-022-05253-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/01/2022] [Indexed: 11/25/2022]
Abstract
Because genotypes within a species commonly differ in traits that influence other species, whole communities, or even ecosystem functions, evolutionary change within one key species may affect the community and ecosystem processes. Here we use experimental mesocosms to test how the evolution of reduced cooperation in rhizobium mutualists in response to 20 years of nitrogen fertilization compares to the effects of rhizobium presence on soil nitrogen availability and plant community composition and diversity. The evolution of reduced rhizobium cooperation caused reductions in soil nitrogen, biological nitrogen fixation, and leaf nitrogen concentrations that were as strong as, or even stronger than, experimental rhizobium inoculation (presence/absence) treatments. Effects of both rhizobium evolution and rhizobium inoculation on legume dominance, plant community composition, and plant species diversity were often smaller in magnitude, but suggest that rhizobium evolution can alter the relative abundance of plant functional groups. Our findings indicate that the consequences of rapid microbial evolution for ecosystems and communities can rival the effects resulting from the presence or abundance of keystone mutualists.
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Affiliation(s)
- Jennifer A Lau
- Kellogg Biological Station & Department of Plant Biology, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, MI, 49060, USA.
- Department of Biology & the Environmental Resilience Institute, Indiana University, 1001 E 3rd St., Bloomington, IN, 47401, USA.
| | - Mark D Hammond
- Kellogg Biological Station & Department of Plant Biology, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, MI, 49060, USA
| | - Jennifer E Schmidt
- Kellogg Biological Station & Department of Plant Biology, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, MI, 49060, USA
- Department of Plant Sciences, University of California, Davis, Davis, CA, 95616, USA
| | - Dylan J Weese
- Kellogg Biological Station & Department of Plant Biology, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, MI, 49060, USA
| | - Wendy H Yang
- Department of Plant Biology, University of Illinois, 505 South Goodwin Ave, Urbana, IL, 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois, 1206 W. Gregory Dr., Urbana, IL, 61801, USA
- Department of Geology, University of Illinois, 1301 West Green St, Urbana, IL, 61801, USA
| | - Katy D Heath
- Department of Plant Biology, University of Illinois, 505 South Goodwin Ave, Urbana, IL, 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois, 1206 W. Gregory Dr., Urbana, IL, 61801, USA
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4
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Burghardt LT, Epstein B, Hoge M, Trujillo DI, Tiffin P. Host-Associated Rhizobial Fitness: Dependence on Nitrogen, Density, Community Complexity, and Legume Genotype. Appl Environ Microbiol 2022; 88:e0052622. [PMID: 35852362 PMCID: PMC9361818 DOI: 10.1128/aem.00526-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 06/24/2022] [Indexed: 11/20/2022] Open
Abstract
The environmental context of the nitrogen-fixing mutualism between leguminous plants and rhizobial bacteria varies over space and time. Variation in resource availability, population density, and composition likely affect the ecology and evolution of rhizobia and their symbiotic interactions with hosts. We examined how host genotype, nitrogen addition, rhizobial density, and community complexity affected selection on 68 rhizobial strains in the Sinorhizobium meliloti-Medicago truncatula mutualism. As expected, host genotype had a substantial effect on the size, number, and strain composition of root nodules (the symbiotic organ). The understudied environmental variable of rhizobial density had a stronger effect on nodule strain frequency than the addition of low nitrogen levels. Higher inoculum density resulted in a nodule community that was less diverse and more beneficial but only in the context of the more selective host genotype. Higher density resulted in more diverse and less beneficial nodule communities with the less selective host. Density effects on strain composition deserve additional scrutiny as they can create feedback between ecological and evolutionary processes. Finally, we found that relative strain rankings were stable across increasing community complexity (2, 3, 8, or 68 strains). This unexpected result suggests that higher-order interactions between strains are rare in the context of nodule formation and development. Our work highlights the importance of examining mechanisms of density-dependent strain fitness and developing theoretical predictions that incorporate density dependence. Furthermore, our results have translational relevance for overcoming establishment barriers in bioinoculants and motivating breeding programs that maintain beneficial plant-microbe interactions across diverse agroecological contexts. IMPORTANCE Legume crops establish beneficial associations with rhizobial bacteria that perform biological nitrogen fixation, providing nitrogen to plants without the economic and greenhouse gas emission costs of chemical nitrogen inputs. Here, we examine the influence of three environmental factors that vary in agricultural fields on strain relative fitness in nodules. In addition to manipulating nitrogen, we also use two biotic variables that have rarely been examined: the rhizobial community's density and complexity. Taken together, our results suggest that (i) breeding legume varieties that select beneficial strains despite environmental variation is possible, (ii) changes in rhizobial population densities that occur routinely in agricultural fields could drive evolutionary changes in rhizobial populations, and (iii) the lack of higher-order interactions between strains will allow the high-throughput assessments of rhizobia winners and losers during plant interactions.
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Affiliation(s)
- Liana T. Burghardt
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
- Plant Science Department, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Brendan Epstein
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Michelle Hoge
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Diana I. Trujillo
- Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota, USA
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
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5
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Batstone RT, Burghardt LT, Heath KD. Phenotypic and genomic signatures of interspecies cooperation and conflict in naturally occurring isolates of a model plant symbiont. Proc Biol Sci 2022; 289:20220477. [PMID: 35858063 PMCID: PMC9277234 DOI: 10.1098/rspb.2022.0477] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Given the need to predict the outcomes of (co)evolution in host-associated microbiomes, whether microbial and host fitnesses tend to trade-off, generating conflict, remains a pressing question. Examining the relationships between host and microbe fitness proxies at both the phenotypic and genomic levels can illuminate the mechanisms underlying interspecies cooperation and conflict. We examined naturally occurring genetic variation in 191 strains of the model microbial symbiont Sinorhizobium meliloti, paired with each of two host Medicago truncatula genotypes in single- or multi-strain experiments to determine how multiple proxies of microbial and host fitness were related to one another and test key predictions about mutualism evolution at the genomic scale, while also addressing the challenge of measuring microbial fitness. We found little evidence for interspecies fitness conflict; loci tended to have concordant effects on both microbe and host fitnesses, even in environments with multiple co-occurring strains. Our results emphasize the importance of quantifying microbial relative fitness for understanding microbiome evolution and thus harnessing microbiomes to improve host fitness. Additionally, we find that mutualistic coevolution between hosts and microbes acts to maintain, rather than erode, genetic diversity, potentially explaining why variation in mutualism traits persists in nature.
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Affiliation(s)
- Rebecca T. Batstone
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, IL 61801, USA
| | - Liana T. Burghardt
- Department of Plant Science, The Pennsylvania State University, 103 Tyson Building, University Park, PA, 16802 USA
| | - Katy D. Heath
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 286 Morrill Hall, 505 South Goodwin Avenue, Urbana, IL 61801, USA
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6
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Epstein B, Burghardt LT, Heath KD, Grillo MA, Kostanecki A, Hämälä T, Young ND, Tiffin P. Combining GWAS and population genomic analyses to characterize coevolution in a legume-rhizobia symbiosis. Mol Ecol 2022. [PMID: 35793264 DOI: 10.1111/mec.16602] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/03/2022] [Accepted: 07/04/2022] [Indexed: 11/28/2022]
Abstract
The mutualism between legumes and rhizobia is clearly the product of past coevolution. However, the nature of ongoing evolution between these partners is less clear. To characterize the nature of recent coevolution between legumes and rhizobia, we used population genomic analysis to characterize selection on functionally annotated symbiosis genes as well as on symbiosis gene candidates identified through a two-species association analysis. For the association analysis, we inoculated each of 202 accessions of the legume host Medicago truncatula with a community of 88 Sinorhizobia (Ensifer) meliloti strains. Multistrain inoculation, which better reflects the ecological reality of rhizobial selection in nature than single-strain inoculation, allows strains to compete for nodulation opportunities and host resources and for hosts to preferentially form nodules and provide resources to some strains. We found extensive host by symbiont, that is, genotype-by-genotype, effects on rhizobial fitness and some annotated rhizobial genes bear signatures of recent positive selection. However, neither genes responsible for this variation nor annotated host symbiosis genes are enriched for signatures of either positive or balancing selection. This result suggests that stabilizing selection dominates selection acting on symbiotic traits and that variation in these traits is under mutation-selection balance. Consistent with the lack of positive selection acting on host genes, we found that among-host variation in growth was similar whether plants were grown with rhizobia or N-fertilizer, suggesting that the symbiosis may not be a major driver of variation in plant growth in multistrain contexts.
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Affiliation(s)
- Brendan Epstein
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Liana T Burghardt
- Department of Plant Sciences, The University of Pennsylvania, University Park, Pennsylvania, USA
| | - Katy D Heath
- Department of Plant Biology, University of Illinois, Urbana, Illinois, USA.,Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
| | - Michael A Grillo
- Department of Biology, Loyola University Chicago, Chicago, Illinois, USA
| | - Adam Kostanecki
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Tuomas Hämälä
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA.,School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Nevin D Young
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA.,Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota, USA
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
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7
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Wardell GE, Hynes MF, Young PJ, Harrison E. Why are rhizobial symbiosis genes mobile? Philos Trans R Soc Lond B Biol Sci 2022; 377:20200471. [PMID: 34839705 PMCID: PMC8628070 DOI: 10.1098/rstb.2020.0471] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 07/28/2021] [Indexed: 11/12/2022] Open
Abstract
Rhizobia are one of the most important and best studied groups of bacterial symbionts. They are defined by their ability to establish nitrogen-fixing intracellular infections within plant hosts. One surprising feature of this symbiosis is that the bacterial genes required for this complex trait are not fixed within the chromosome, but are encoded on mobile genetic elements (MGEs), namely plasmids or integrative and conjugative elements. Evidence suggests that many of these elements are actively mobilizing within rhizobial populations, suggesting that regular symbiosis gene transfer is part of the ecology of rhizobial symbionts. At first glance, this is counterintuitive. The symbiosis trait is highly complex, multipartite and tightly coevolved with the legume hosts, while transfer of genes can be costly and disrupt coadaptation between the chromosome and the symbiosis genes. However, horizontal gene transfer is a process driven not only by the interests of the host bacterium, but also, and perhaps predominantly, by the interests of the MGEs that facilitate it. Thus understanding the role of horizontal gene transfer in the rhizobium-legume symbiosis requires a 'mobile genetic element's-eye view' on the ecology and evolution of this important symbiosis. This article is part of the theme issue 'The secret lives of microbial mobile genetic elements'.
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Affiliation(s)
- Grace E. Wardell
- Department of Animal Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 1EA, UK
| | - Michael F. Hynes
- Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - Peter J. Young
- Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK
| | - Ellie Harrison
- Department of Animal Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 1EA, UK
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8
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Easterday CA, Kendig AE, Lacroix C, Seabloom EW, Borer ET. Long-term nitrogen enrichment mediates the effects of nitrogen supply and co-inoculation on a viral pathogen. Ecol Evol 2022; 12:e8450. [PMID: 35136545 PMCID: PMC8809429 DOI: 10.1002/ece3.8450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 11/02/2021] [Accepted: 11/05/2021] [Indexed: 11/12/2022] Open
Abstract
Host nutrient supply can mediate host-pathogen and pathogen-pathogen interactions. In terrestrial systems, plant nutrient supply is mediated by soil microbes, suggesting a potential role of soil microbes in plant diseases beyond soil-borne pathogens and induced plant defenses. Long-term nitrogen (N) enrichment can shift pathogenic and nonpathogenic soil microbial community composition and function, but it is unclear if these shifts affect plant-pathogen and pathogen-pathogen interactions. In a growth chamber experiment, we tested the effect of long-term N enrichment on infection by Barley Yellow Dwarf Virus (BYDV-PAV) and Cereal Yellow Dwarf Virus (CYDV-RPV), aphid-vectored RNA viruses, in a grass host. We inoculated sterilized growing medium with soil collected from a long-term N enrichment experiment (ambient, low, and high N soil treatments) to isolate effects mediated by the soil microbial community. We crossed soil treatments with a N supply treatment (low, high) and virus inoculation treatment (mock-, singly-, and co-inoculated) to evaluate the effects of long-term N enrichment on plant-pathogen and pathogen-pathogen interactions, as mediated by N availability. We measured the proportion of plants infected (i.e., incidence), plant biomass, and leaf chlorophyll content. BYDV-PAV incidence (0.96) declined with low N soil (to 0.46), high N supply (to 0.61), and co-inoculation (to 0.32). Low N soil mediated the effect of N supply on BYDV-PAV: instead of N supply reducing BYDV-PAV incidence, the incidence increased. Additionally, ambient and low N soil ameliorated the negative effect of co-inoculation on BYDV-PAV incidence. BYDV-PAV infection only reduced chlorophyll when plants were grown with low N supply and ambient N soil. There were no significant effects of long-term N soil on CYDV-RPV incidence. Soil inoculant with different levels of long-term N enrichment had different effects on host-pathogen and pathogen-pathogen interactions, suggesting that shifts in soil microbial communities with long-term N enrichment may mediate disease dynamics.
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Affiliation(s)
- Casey A. Easterday
- Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSt. PaulMinnesotaUSA
- Present address:
Carlson School of ManagementUniversity of MinnesotaMinneapolisMinnesotaUSA
| | - Amy E. Kendig
- Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSt. PaulMinnesotaUSA
| | - Christelle Lacroix
- Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSt. PaulMinnesotaUSA
- Present address:
Pathologie VégétaleINRAEMontfavetFrance
| | - Eric W. Seabloom
- Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSt. PaulMinnesotaUSA
| | - Elizabeth T. Borer
- Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSt. PaulMinnesotaUSA
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9
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Liu Y, Ma B, Chen W, Schlaeppi K, Erb M, Stirling E, Hu L, Wang E, Zhang Y, Zhao K, Lu Z, Ye S, Xu J. Rhizobium Symbiotic Capacity Shapes Root-Associated Microbiomes in Soybean. Front Microbiol 2021; 12:709012. [PMID: 34925249 PMCID: PMC8678110 DOI: 10.3389/fmicb.2021.709012] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 11/09/2021] [Indexed: 12/26/2022] Open
Abstract
Root-microbiome interactions are of central importance for plant performance and yield. A distinctive feature of legumes is that they engage in symbiosis with N2-fixing rhizobia. If and how the rhizobial symbiotic capacity modulates root-associated microbiomes are still not yet well understood. We determined root-associated microbiomes of soybean inoculated with wild type (WT) or a noeI mutant of Bradyrhizobium diazoefficiens USDA 110 by amplicon sequencing. UPLC-MS/MS was used to analyze root exudates. The noeI gene is responsible for fucose-methylation of Nod factor secreted by USDA 110 WT strain. Soybean roots inoculated with the noeI mutant showed a significant decrease in nodulation and root-flavonoid exudation compared to roots inoculated with WT strain. The noeI mutant-inoculated roots exhibited strong changes in microbiome assembly in the rhizosphere and rhizoplane, including reduced diversity, changed co-occurrence interactions and a substantial depletion of root microbes. Root exudates and soil physiochemical properties were significantly correlated with microbial community shift in the rhizosphere between different rhizobial treatments. These results illustrate that rhizobial symbiotic capacity dramatically alters root-associated microbiomes, in which root exudation and edaphic patterns play a vital role. This study has important implications for understanding the evolution of plant-microbiome interactions.
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Affiliation(s)
- Yuanhui Liu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China.,China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
| | - Bin Ma
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China.,Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, China
| | - Wenfeng Chen
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences and Rhizobium Research Center, China Agricultural University, Ministry of Agriculture Key Laboratory of Soil Microbiology, Beijing, China
| | - Klaus Schlaeppi
- Department of Environmental Sciences, University of Basel, Basel, Switzerland.,Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Matthias Erb
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Erinne Stirling
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China.,Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, China.,Acid Sulfate Soils Centre, School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
| | - Lingfei Hu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Entao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México City, México
| | - Yunzeng Zhang
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, China
| | - Kankan Zhao
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Zhijiang Lu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Shudi Ye
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Jianming Xu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
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10
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Wendlandt CE, Helliwell E, Roberts M, Nguyen KT, Friesen ML, von Wettberg E, Price P, Griffitts JS, Porter SS. Decreased coevolutionary potential and increased symbiont fecundity during the biological invasion of a legume-rhizobium mutualism. Evolution 2021; 75:731-747. [PMID: 33433925 DOI: 10.1111/evo.14164] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 10/08/2020] [Accepted: 12/07/2020] [Indexed: 12/20/2022]
Abstract
Although most invasive species engage in mutualism, we know little about how mutualism evolves as partners colonize novel environments. Selection on cooperation and standing genetic variation for mutualism traits may differ between a mutualism's invaded and native ranges, which could alter cooperation and coevolutionary dynamics. To test for such differences, we compare mutualism traits between invaded- and native-range host-symbiont genotype combinations of the weedy legume, Medicago polymorpha, and its nitrogen-fixing rhizobium symbiont, Ensifer medicae, which have coinvaded North America. We find that mutualism benefits for plants are indistinguishable between invaded- and native-range symbioses. However, rhizobia gain greater fitness from invaded-range mutualisms than from native-range mutualisms, and this enhancement of symbiont fecundity could increase the mutualism's spread by increasing symbiont availability during plant colonization. Furthermore, mutualism traits in invaded-range symbioses show lower genetic variance and a simpler partitioning of genetic variance between host and symbiont sources, compared to native-range symbioses. This suggests that biological invasion has reduced mutualists' potential to respond to coevolutionary selection. Additionally, rhizobia bearing a locus (hrrP) that can enhance symbiotic fitness have more exploitative phenotypes in invaded-range than in native-range symbioses. These findings highlight the impacts of biological invasion on the evolution of mutualistic interactions.
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Affiliation(s)
- Camille E Wendlandt
- School of Biological Sciences, Washington State University, Vancouver, Washington
| | - Emily Helliwell
- School of Biological Sciences, Washington State University, Vancouver, Washington
| | - Miles Roberts
- School of Biological Sciences, Washington State University, Vancouver, Washington
| | - Kyle T Nguyen
- School of Biological Sciences, Washington State University, Vancouver, Washington
| | - Maren L Friesen
- Department of Plant Pathology, Department of Crop and Soil Sciences, Washington State University, Pullman, Washington
| | - Eric von Wettberg
- Department of Plant and Soil Science, Gund Institute for the Environment, University of Vermont, Burlington, Vermont
| | - Paul Price
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan
| | - Joel S Griffitts
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, Utah
| | - Stephanie S Porter
- School of Biological Sciences, Washington State University, Vancouver, Washington
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11
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Epstein B, Tiffin P. Comparative genomics reveals high rates of horizontal transfer and strong purifying selection on rhizobial symbiosis genes. Proc Biol Sci 2021; 288:20201804. [PMID: 33402066 DOI: 10.1098/rspb.2020.1804] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Horizontal transfer (HT) alters the repertoire of symbiosis genes in rhizobial genomes and may play an important role in the on-going evolution of the rhizobia-legume symbiosis. To gain insight into the extent of HT of symbiosis genes with different functional roles (nodulation, N-fixation, host benefit and rhizobial fitness), we conducted comparative genomic and selection analyses of the full-genome sequences from 27 rhizobial genomes. We find that symbiosis genes experience high rates of HT among rhizobial lineages but also bear signatures of purifying selection (low Ka : Ks). HT and purifying selection appear to be particularly strong in genes involved in initiating the symbiosis (e.g. nodulation) and in genome-wide association candidates for mediating benefits provided to the host. These patterns are consistent with rhizobia adapting to the host environment through the loss and gain of symbiosis genes, but not with host-imposed positive selection driving divergence of symbiosis genes through recurring bouts of positive selection.
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Affiliation(s)
- Brendan Epstein
- Department of Plant and Microbial Biology, University of Minnesota, St Paul, MN, USA
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St Paul, MN, USA
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12
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Bamba M, Aoki S, Kajita T, Setoguchi H, Watano Y, Sato S, Tsuchimatsu T. Massive rhizobial genomic variation associated with partner quality in Lotus-Mesorhizobium symbiosis. FEMS Microbiol Ecol 2020; 96:5917975. [PMID: 33016310 DOI: 10.1093/femsec/fiaa202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 09/29/2020] [Indexed: 11/14/2022] Open
Abstract
Variation in partner quality is commonly observed in diverse cooperative relationships, despite the theoretical prediction that selection favoring high-quality partners should eliminate such variation. Here, we investigated how genetic variation in partner quality could be maintained in the nitrogen-fixing mutualism between Lotus japonicus and Mesorhizobium bacteria. We reconstructed de novo assembled full-genome sequences from nine rhizobial symbionts, finding massive variation in the core genome and the similar symbiotic islands, indicating recent horizontal gene transfer (HGT) of the symbiosis islands into diverse Mesorhizobium lineages. A cross-inoculation experiment using 9 sequenced rhizobial symbionts and 15 L. japonicus accessions revealed extensive quality variation represented by plant growth phenotypes, including genotype-by-genotype interactions. Variation in quality was not associated with the presence/absence variation in known symbiosis-related genes in the symbiosis island; rather, it showed significant correlation with the core genome variation. Given the recurrent HGT of the symbiosis islands into diverse Mesorhizobium strains, local Mesorhizobium communities could serve as a major source of variation for core genomes, which might prevent variation in partner quality from fixing, even in the presence of selection favoring high-quality partners. These findings highlight the novel role of HGT of symbiosis islands in maintaining partner quality variation in the legume-rhizobia symbiosis.
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Affiliation(s)
- Masaru Bamba
- Department of Biology (Frontier Science Program), Graduate School of Science and Engineering, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan.,Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
| | - Seishiro Aoki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Tadashi Kajita
- Iriomote Station, Tropical Biosphere Research Center, The University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa 907-1541, Japan
| | - Hiroaki Setoguchi
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Yasuyuki Watano
- Department of Biology, Graduate School of Science, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan
| | - Shusei Sato
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
| | - Takashi Tsuchimatsu
- Department of Biology, Graduate School of Science, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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13
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Batstone RT, Peters MAE, Simonsen AK, Stinchcombe JR, Frederickson ME. Environmental variation impacts trait expression and selection in the legume-rhizobium symbiosis. AMERICAN JOURNAL OF BOTANY 2020; 107:195-208. [PMID: 32064599 DOI: 10.1002/ajb2.1432] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 11/04/2019] [Indexed: 05/22/2023]
Abstract
PREMISE The ecological outcomes of mutualism are well known to shift across abiotic or biotic environments, but few studies have addressed how different environments impact evolutionary responses, including the intensity of selection on and the expression of genetic variance in key mutualism-related traits. METHODS We planted 30 maternal lines of the legume Medicago lupulina in four field common gardens and compared our measures of selection on and genetic variance in nodulation, a key trait reflecting legume investment in the symbiosis, with those from a previous greenhouse experiment using the same 30 M. lupulina lines. RESULTS We found that both the mean and genetic variance for nodulation were much greater in the greenhouse than in the field and that the form of selection on nodulation significantly differed across environments. We also found significant genotype-by-environment (G × E) effects for fitness-related traits that were generated by differences in the rank order of plant lines among environments. CONCLUSIONS Overall, our results suggest that the expression of genotypic variation and selection on nodulation differ across environments. In the field, significant rank-order changes for plant fitness potentially help maintain genetic variation in natural populations, even in the face of directional or stabilizing selection.
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Affiliation(s)
- Rebecca T Batstone
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
- Carl Woese Institute for Genomic Biology, University of Illinois at Champaign-Urbana, Urbana, IL, 61801, USA
| | - Madeline A E Peters
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Anna K Simonsen
- Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia
| | - John R Stinchcombe
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
- Koffler Scientific Reserve, University of Toronto, King, ON, L7B 1K5, Canada
| | - Megan E Frederickson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
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14
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Heath KD, Podowski JC, Heniff S, Klinger CR, Burke PV, Weese DJ, Yang WH, Lau JA. Light availability and rhizobium variation interactively mediate the outcomes of legume-rhizobium symbiosis. AMERICAN JOURNAL OF BOTANY 2020; 107:229-238. [PMID: 32072629 DOI: 10.1002/ajb2.1435] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 12/08/2019] [Indexed: 05/22/2023]
Abstract
PREMISE Nutrients, light, water, and temperature are key factors limiting the growth of individual plants in nature. Mutualistic interactions between plants and microbes often mediate resource limitation for both partners. In the mutualism between legumes and rhizobia, plants provide rhizobia with carbon in exchange for fixed nitrogen. Because partner quality in mutualisms is genotype-dependent, within-species genetic variation is expected to alter the responses of mutualists to changes in the resource environment. Here we ask whether partner quality variation in rhizobia mediates the response of host plants to changing light availability, and conversely, whether light alters the expression of partner quality variation. METHODS We inoculated clover hosts with 11 strains of Rhizobium leguminosarum that differed in partner quality, grew plants under either ambient or low light conditions in the greenhouse, and measured plant growth, nodule traits, and foliar nutrient composition. RESULTS Light availability and rhizobium inoculum interactively determined plant growth, and variation in rhizobium partner quality was more apparent in ambient light. CONCLUSIONS Our results suggest that variation in the costs and benefits of rhizobium symbionts mediate host responses to light availability and that rhizobium strain variation might more important in higher-light environments. Our work adds to a growing appreciation for the role of microbial intraspecific and interspecific diversity in mediating extended phenotypes in their hosts and suggests an important role for light availability in the ecology and evolution of legume-rhizobium symbiosis.
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Affiliation(s)
- Katy D Heath
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL, 61801, USA
| | - Justin C Podowski
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL, 61801, USA
| | - Stephanie Heniff
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL, 61801, USA
| | - Christie R Klinger
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL, 61801, USA
| | - Patricia V Burke
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL, 61801, USA
| | - Dylan J Weese
- Department of Biology, St. Ambrose University, Davenport, IA, 52803, USA
| | - Wendy H Yang
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL, 61801, USA
| | - Jennifer A Lau
- W. K. Kellogg Biological Station and Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA
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15
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Friel CA, Friesen ML. Legumes Modulate Allocation to Rhizobial Nitrogen Fixation in Response to Factorial Light and Nitrogen Manipulation. FRONTIERS IN PLANT SCIENCE 2019; 10:1316. [PMID: 31749816 PMCID: PMC6848274 DOI: 10.3389/fpls.2019.01316] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 09/23/2019] [Indexed: 05/25/2023]
Abstract
The costs and benefits that define gain from trade in resource mutualisms depend on resource availability. Optimal partitioning theory predicts that allocation to direct uptake versus trade will be determined by both the relative benefit of the resource acquired through trade and the relative cost of the resource being traded away. While the costs and benefits of carbon:nitrogen exchange in the legume-rhizobia symbiosis have been examined in depth with regards to mineral nitrogen availability, the effects of varying carbon costs are rarely considered. Using a growth chamber experiment, we measured plant growth and symbiosis investment in the model legume Medicago truncatula and its symbiont Ensifer medicae across varying nitrogen and light environments. We demonstrate that plants modulate their allocation to roots and nodules as their return on investment varies according to external nitrogen and carbon availabilities. We find empirical evidence that plant allocation to nodules responds to carbon availability, but that this depends upon the nitrogen environment. In particular, at low nitrogen-where rhizobia provided the majority of nitrogen for plant growth-relative nodule allocation increased when carbon limitation was alleviated with high light levels. Legumes' context-dependent modulation of resource allocation to rhizobia thus prevents this interaction from becoming parasitic even in low-light, high-nitrogen environments where carbon is costly and nitrogen is readily available.
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Affiliation(s)
- Colleen A. Friel
- Department of Plant Biology, Michigan State University, East Lansing, MI, United States
- BEACON Center for Evolution in Action, Michigan State University, East Lansing, MI, United States
| | - Maren L. Friesen
- Department of Plant Biology, Michigan State University, East Lansing, MI, United States
- BEACON Center for Evolution in Action, Michigan State University, East Lansing, MI, United States
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16
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Simonsen AK, Barrett LG, Thrall PH, Prober SM. Novel model-based clustering reveals ecologically differentiated bacterial genomes across a large climate gradient. Ecol Lett 2019; 22:2077-2086. [PMID: 31612601 DOI: 10.1111/ele.13389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 07/28/2019] [Accepted: 08/19/2019] [Indexed: 12/19/2022]
Abstract
A pervasive challenge in microbial ecology is understanding the genetic level where ecological units can be differentiated. Ecological differentiation often occurs at fine genomic levels, yet it is unclear how to utilise ecological information to define ecotypes given the breadth of environmental variation among microbial taxa. Here, we present an analytical framework that infers clusters along genome-based microbial phylogenies according to shared environmental responses. The advantage of our approach is the ability to identify genomic clusters that best fit complex environmental information whilst characterising cluster niches through model predictions. We apply our method to determine climate-associated ecotypes in populations of nitrogen-fixing symbionts using whole genomes, explicitly sampled to detect climate differentiation across a heterogeneous landscape. Although soil and plant host characteristics strongly influence distribution patterns of inferred ecotypes, our flexible statistical method enabled us to identify climate-associated genomic clusters using environmental data, providing solid support for ecological specialisation in soil symbionts.
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Affiliation(s)
- Anna K Simonsen
- Research School of Biology, Australian National University, Acton, ACT, Australia.,Land and Water, Commonwealth Scientific and Industrial Research Organisation, Acton, ACT, Australia
| | - Luke G Barrett
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Acton, ACT, Australia
| | - Peter H Thrall
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Acton, ACT, Australia
| | - Suzanne M Prober
- Land and Water, Commonwealth Scientific and Industrial Research Organisation, Acton, ACT, Australia
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17
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Wood CW, Stinchcombe JR. A window into the transcriptomic basis of genotype-by-genotype interactions in the legume-rhizobia mutualism. Mol Ecol 2019; 26:5869-5871. [PMID: 29144582 DOI: 10.1111/mec.14370] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 09/20/2017] [Indexed: 11/29/2022]
Abstract
The maintenance of genetic variation in the benefits provided by mutualists is an evolutionary puzzle (Heath & Stinchcombe, ). Over time, natural selection should favour the benefit strategy that confers the highest fitness, eroding genetic variation in partner quality. Yet abundant genetic variation in partner quality exists in many systems (Heath & Stinchcombe, ). One possible resolution to this puzzle is that the genetic identity of both a host and its partner affects the benefits each mutualist provides to the other, a pattern known as a genotype-by-genotype interaction (Figure ). Mounting evidence suggests that genotype-by-genotype interactions between partners are pervasive at the phenotypic level (Barrett, Zee, Bever, Miller, & Thrall, ; Heath, ; Hoeksema & Thompson, ). Ultimately, however, to link these phenotypic patterns to the maintenance of genetic variation in mutualisms we need to answer two questions: How much variation in mutualism phenotypes is attributable to genotype-by-genotype interactions, and what mutualistic functions are influenced by each partner and by the interaction between their genomes? In this issue of Molecular Ecology, Burghardt et al. (2017) use transcriptomics to address both questions in the legume-rhizobia mutualism.
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Affiliation(s)
- Corlett W Wood
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
| | - John R Stinchcombe
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.,Koffler Scientific Reserve, University of Toronto, Toronto, ON, Canada
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18
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O’Brien AM, Sawers RJH, Ross-Ibarra J, Strauss SY. Evolutionary Responses to Conditionality in Species Interactions across Environmental Gradients. Am Nat 2018; 192:715-730. [DOI: 10.1086/700118] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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19
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Guerrero J, Andrello M, Burgarella C, Manel S. Soil environment is a key driver of adaptation in Medicago truncatula: new insights from landscape genomics. THE NEW PHYTOLOGIST 2018; 219:378-390. [PMID: 29696659 DOI: 10.1111/nph.15171] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 03/14/2018] [Indexed: 05/22/2023]
Abstract
Spatial differences in environmental selective pressures interact with the genomes of organisms, ultimately leading to local adaptation. Landscape genomics is an emergent research area that uncovers genome-environment associations, thus allowing researchers to identify candidate loci for adaptation to specific environmental variables. In the present study, we used latent factor mixed models (LFMMs) and Moran spectral outlier detection/randomization (MSOD-MSR) to identify candidate loci for adaptation to 10 environmental variables (climatic, soil and atmospheric) among 43 515 single nucleotide polymorphisms (SNPs) from 202 accessions of the model legume Medicago truncatula. Soil variables were associated with a large number of candidate loci identified through both LFMMs and MSOD-MSR. Genes tagged by candidate loci associated with drought and salinity are involved in the response to biotic and abiotic stresses, while those tagged by candidates associated with soil nitrogen and atmospheric nitrogen, participate in the legume-rhizobia symbiosis. Candidate SNPs identified through both LFMMs and MSOD-MSR explained up to 56% of variance in flowering traits. Our findings highlight the importance of soil in driving adaptation in the system and elucidate the basis of evolutionary potential of M. truncatula to respond to global climate change and anthropogenic disruption of the nitrogen cycle.
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Affiliation(s)
- Jimena Guerrero
- CEFE-CNRS, Centre D'Ecologie Fonctionelle et Evolutive, Route de Mende, 34090, Montpellier, France
| | - Marco Andrello
- CEFE-CNRS, Centre D'Ecologie Fonctionelle et Evolutive, Route de Mende, 34090, Montpellier, France
| | - Concetta Burgarella
- UMR DIADE Institut de Recherche pour le Developpement (IRD), Centre de Montpellier, BP 64501, Montpellier Cedex 5, France
- UMR AGAP Centre de Coopération International en Recherche Agronomique pour le Développement (CIRAD), Avenue Agropolis, 34398, Montpellier, France
| | - Stephanie Manel
- CEFE-CNRS, Centre D'Ecologie Fonctionelle et Evolutive, Route de Mende, 34090, Montpellier, France
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20
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Batstone RT, Carscadden KA, Afkhami ME, Frederickson ME. Using niche breadth theory to explain generalization in mutualisms. Ecology 2018; 99:1039-1050. [PMID: 29453827 DOI: 10.1002/ecy.2188] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 12/12/2017] [Accepted: 01/22/2018] [Indexed: 02/02/2023]
Abstract
For a mutualism to remain evolutionarily stable, theory predicts that mutualists should limit their associations to high-quality partners. However, most mutualists either simultaneously or sequentially associate with multiple partners that confer the same type of reward. By viewing mutualisms through the lens of niche breadth evolution, we outline how the environment shapes partner availability and relative quality, and ultimately a focal mutualist's partner breadth. We argue that mutualists that associate with multiple partners may have a selective advantage compared to specialists for many reasons, including sampling, complementarity, and portfolio effects, as well as the possibility that broad partner breadth increases breadth along other niche axes. Furthermore, selection for narrow partner breadth is unlikely to be strong when the environment erodes variation in partner quality, reduces the costs of interacting with low-quality partners, spatially structures partner communities, or decreases the strength of mutualism. Thus, we should not be surprised that most mutualists have broad partner breadth, even if it allows for ineffective partners to persist.
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Affiliation(s)
- Rebecca T Batstone
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
| | - Kelly A Carscadden
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada.,Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, Colorado, 80309, USA
| | - Michelle E Afkhami
- Department of Biology, University of Miami, Coral Gables, Florida, 33146, USA
| | - Megan E Frederickson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
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21
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What Microbial Population Genomics Has Taught Us About Speciation. POPULATION GENOMICS: MICROORGANISMS 2018. [DOI: 10.1007/13836_2018_10] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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22
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Schmidt JE, Weese DJ, Lau JA. Long-term agricultural management does not alter the evolution of a soybean-rhizobium mutualism. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2017; 27:2487-2496. [PMID: 28921808 DOI: 10.1002/eap.1625] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 08/11/2017] [Accepted: 08/29/2017] [Indexed: 06/07/2023]
Abstract
Leguminous crops, like soybeans, often rely on biologically fixed nitrogen via their symbiosis with rhizobia rather than synthetic nitrogen inputs. However, agricultural management practices may influence the effectiveness of biological nitrogen fixation (BNF). While the ecological effects of agricultural management on rhizobia have received some attention, the evolutionary effects have been neglected in comparison. Resource mutualism theory predicts that evolutionary effects are likely, however. Both fertilization and tillage are predicted to cause the evolution of rhizobia that provide fewer growth benefits to plant hosts and fix less nitrogen. This study capitalized on a Long-Term Ecological Research experiment that manipulated agricultural management practices in a corn-soybean-wheat row crop system for 24 yr to investigate whether four different management practices (conventional, no-till, low chemical input, and certified organic) cause rhizobia populations to evolve to become more or less cooperative. We found little evidence that 24 yr of varying management practices affect the net growth benefits rhizobia provide to soybeans, although soybean plants inoculated with soils collected from conventional treatments tended to have lower BNF rates than plants inoculated with soils from the no-till, low input, and organic management treatments. These findings suggest that rhizobia will continue to provide adequate growth benefits to leguminous crops in the future, even in intensively managed systems.
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Affiliation(s)
- Jennifer E Schmidt
- Kellogg Biological Station, Michigan State University, 3700 E Gull Lake Drive, Hickory Corners, Michigan, 49060, USA
- Pomoma College, Claremont, California, 91711, USA
| | - Dylan J Weese
- Kellogg Biological Station, Michigan State University, 3700 E Gull Lake Drive, Hickory Corners, Michigan, 49060, USA
- Saint Ambrose University, Davenport, Iowa, 52803, USA
| | - Jennifer A Lau
- Kellogg Biological Station, Michigan State University, 3700 E Gull Lake Drive, Hickory Corners, Michigan, 49060, USA
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23
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Harrison TL, Wood CW, Heath KD, Stinchcombe JR. Geographically structured genetic variation in the
Medicago lupulina
–
Ensifer
mutualism. Evolution 2017; 71:1787-1801. [DOI: 10.1111/evo.13268] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 04/08/2017] [Accepted: 04/15/2017] [Indexed: 12/30/2022]
Affiliation(s)
- Tia L. Harrison
- Department of Ecology and Evolutionary BiologyUniversity of Toronto 25 Willcocks Street Toronto Ontario Canada M5S 3B2
| | - Corlett W. Wood
- Department of Ecology and Evolutionary BiologyUniversity of Toronto 25 Willcocks Street Toronto Ontario Canada M5S 3B2
| | - Katy D. Heath
- Department of Plant BiologyUniversity of Illinois 505 S. Goodwin Avenue Urbana Illinois 61801
| | - John R. Stinchcombe
- Department of Ecology and Evolutionary BiologyUniversity of Toronto 25 Willcocks Street Toronto Ontario Canada M5S 3B2
- Centre for Genome Evolution and FunctionUniversity of Toronto 25 Willcocks Street Toronto Ontario Canada M5S 3B2
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24
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Grillo MA, Stinchcombe JR, Heath KD. Nitrogen addition does not influence pre-infection partner choice in the legume-rhizobium symbiosis. AMERICAN JOURNAL OF BOTANY 2016; 103:1763-1770. [PMID: 27671532 DOI: 10.3732/ajb.1600090] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 08/09/2016] [Indexed: 05/26/2023]
Abstract
PREMISE OF THE STUDY Resource mutualisms such as the symbiosis between legumes and nitrogen-fixing rhizobia are context dependent and are sensitive to various aspects of the environment, including nitrogen (N) addition. Mutualist hosts such as legumes are also thought to use mechanisms such as partner choice to discriminate among potential symbionts that vary in partner quality (fitness benefits conferred to hosts) and thus impose selection on rhizobium populations. Together, context dependency and partner choice might help explain why the legume-rhizobium mutualism responds evolutionarily to N addition, since plant-mediated selection that shifts in response to N might be expected to favor different rhizobium strains in different N environments. METHODS We test for the influence of context dependency on partner choice in the model legume, Medicago truncatula, using a factorial experiments with three plant families across three N levels with a mixed inoculation of three rhizobia strains. KEY RESULTS Neither the relative frequencies of rhizobium strains occupying host nodules, nor the size of those nodules, differed in response to N level. CONCLUSIONS Despite the lack of context dependence, plant genotypes respond very differently to mixed populations of rhizobia, suggesting that these traits are genetically variable and thus could evolve in response to longer-term increases in N.
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Affiliation(s)
- Michael A Grillo
- University of Illinois, Department of Plant Biology, Urbana, Illinois 61801, USA
| | - John R Stinchcombe
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2
| | - Katy D Heath
- University of Illinois, Department of Plant Biology, Urbana, Illinois 61801, USA
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25
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Heath KD, Grillo MA. Rhizobia: tractable models for bacterial evolutionary ecology. Environ Microbiol 2016; 18:4307-4311. [DOI: 10.1111/1462-2920.13492] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Katy D. Heath
- Department of Plant Biology; University of Illinois at Urbana-Champaign; 265 Morrill Hall, 505 S. Goodwin Ave Urbana IL 61801, USA
| | - Michael A. Grillo
- Department of Plant Biology; University of Illinois at Urbana-Champaign; 265 Morrill Hall, 505 S. Goodwin Ave Urbana IL 61801, USA
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26
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Pérez Carrascal OM, VanInsberghe D, Juárez S, Polz MF, Vinuesa P, González V. Population genomics of the symbiotic plasmids of sympatric nitrogen-fixing Rhizobium species associated with Phaseolus vulgaris. Environ Microbiol 2016; 18:2660-76. [PMID: 27312778 DOI: 10.1111/1462-2920.13415] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 06/13/2016] [Indexed: 11/28/2022]
Abstract
Cultivated common beans are the primary protein source for millions of people around the world who subsist on low-input agriculture, enabled by the symbiotic N2 -fixation these legumes perform in association with rhizobia. Within a single agricultural plot, multiple Rhizobium species can nodulate bean roots, but it is unclear how genetically isolated these species remain in sympatry. To better understand this issue, we sequenced and compared the genomes of 33 strains isolated from the rhizosphere and root nodules of a particular bean variety grown in the same agricultural plot. We found that the Rhizobium species we observed coexist with low genetic recombination across their core genomes. Accessory plasmids thought to be necessary for the saprophytic lifestyle in soil show similar levels of genetic isolation, but with higher rates of recombination than the chromosomes. However, the symbiotic plasmids are extremely similar, with high rates of recombination and do not appear to have co-evolved with the chromosome or accessory plasmids. Therefore, while Rhizobium species are genetically isolated units within the microbial community, a common symbiotic plasmid allows all Rhizobium species to engage in symbiosis with the same host in a single agricultural plot.
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Affiliation(s)
- Olga M Pérez Carrascal
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - David VanInsberghe
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Soledad Juárez
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Martin F Polz
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Pablo Vinuesa
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Víctor González
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
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