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Göktay M, Fulgione A, Hancock AM. A New Catalog of Structural Variants in 1,301 A. thaliana Lines from Africa, Eurasia, and North America Reveals a Signature of Balancing Selection at Defense Response Genes. Mol Biol Evol 2021; 38:1498-1511. [PMID: 33247723 PMCID: PMC8042739 DOI: 10.1093/molbev/msaa309] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Genomic variation in the model plant Arabidopsis thaliana has been extensively used to understand evolutionary processes in natural populations, mainly focusing on single-nucleotide polymorphisms. Conversely, structural variation has been largely ignored in spite of its potential to dramatically affect phenotype. Here, we identify 155,440 indels and structural variants ranging in size from 1 bp to 10 kb, including presence/absence variants (PAVs), inversions, and tandem duplications in 1,301 A. thaliana natural accessions from Morocco, Madeira, Europe, Asia, and North America. We show evidence for strong purifying selection on PAVs in genes, in particular for housekeeping genes and homeobox genes, and we find that PAVs are concentrated in defense-related genes (R-genes, secondary metabolites) and F-box genes. This implies the presence of a "core" genome underlying basic cellular processes and a "flexible" genome that includes genes that may be important in spatially or temporally varying selection. Further, we find an excess of intermediate frequency PAVs in defense response genes in nearly all populations studied, consistent with a history of balancing selection on this class of genes. Finally, we find that PAVs in genes involved in the cold requirement for flowering (vernalization) and drought response are strongly associated with temperature at the sites of origin.
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Affiliation(s)
- Mehmet Göktay
- Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Andrea Fulgione
- Max Planck Institute for Plant Breeding Research, Cologne, Germany
| | - Angela M Hancock
- Max Planck Institute for Plant Breeding Research, Cologne, Germany
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Calvo-Baltanás V, Wang J, Chae E. Hybrid Incompatibility of the Plant Immune System: An Opposite Force to Heterosis Equilibrating Hybrid Performances. FRONTIERS IN PLANT SCIENCE 2021; 11:576796. [PMID: 33717206 PMCID: PMC7953517 DOI: 10.3389/fpls.2020.576796] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 12/28/2020] [Indexed: 06/12/2023]
Abstract
Hybridization is a core element in modern rice breeding as beneficial combinations of two parental genomes often result in the expression of heterosis. On the contrary, genetic incompatibility between parents can manifest as hybrid necrosis, which leads to tissue necrosis accompanied by compromised growth and/or reduced reproductive success. Genetic and molecular studies of hybrid necrosis in numerous plant species revealed that such self-destructing symptoms in most cases are attributed to autoimmunity: plant immune responses are inadvertently activated in the absence of pathogenic invasion. Autoimmunity in hybrids predominantly occurs due to a conflict involving a member of the major plant immune receptor family, the nucleotide-binding domain and leucine-rich repeat containing protein (NLR; formerly known as NBS-LRR). NLR genes are associated with disease resistance traits, and recent population datasets reveal tremendous diversity in this class of immune receptors. Cases of hybrid necrosis involving highly polymorphic NLRs as major causes suggest that diversified R gene repertoires found in different lineages would require a compatible immune match for hybridization, which is a prerequisite to ensure increased fitness in the resulting hybrids. In this review, we overview recent genetic and molecular findings on hybrid necrosis in multiple plant species to provide an insight on how the trade-off between growth and immunity is equilibrated to affect hybrid performances. We also revisit the cases of hybrid weakness in which immune system components are found or implicated to play a causative role. Based on our understanding on the trade-off, we propose that the immune system incompatibility in plants might play an opposite force to restrict the expression of heterosis in hybrids. The antagonism is illustrated under the plant fitness equilibrium, in which the two extremes lead to either hybrid necrosis or heterosis. Practical proposition from the equilibrium model is that breeding efforts for combining enhanced disease resistance and high yield shall be achieved by balancing the two forces. Reverse breeding toward utilizing genomic data centered on immune components is proposed as a strategy to generate elite hybrids with balanced immunity and growth.
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Karasov TL, Barrett L, Hershberg R, Bergelson J. Similar levels of gene content variation observed for Pseudomonas syringae populations extracted from single and multiple host species. PLoS One 2017; 12:e0184195. [PMID: 28880925 PMCID: PMC5589212 DOI: 10.1371/journal.pone.0184195] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 08/18/2017] [Indexed: 12/22/2022] Open
Abstract
Bacterial strains of the same species collected from different hosts frequently exhibit differences in gene content. In the ubiquitous plant pathogen Pseudomonas syringae, more than 30% of genes encoded by each strain are not conserved among strains colonizing other host species. Although they are often implicated in host specificity, the role of this large fraction of the genome in host-specific adaptation is largely unexplored. Here, we sought to relate variation in gene content between strains infecting different species to variation that persists between strains on the same host. We fully sequenced a collection of P. syringae strains collected from wild Arabidopsis thaliana populations in the Midwestern United States. We then compared patterns of variation observed in gene content within these A. thaliana-isolated strains to previously published P. syringae sequence from strains collected on a diversity of crop species. We find that strains collected from the same host, A. thaliana, differ in gene content by 21%, 2/3 the level of gene content variation observed across strains collected from different hosts. Furthermore, the frequency with which specific genes are present among strains collected within the same host and among strains collected from different hosts is highly correlated. This implies that most gene content variation is maintained irrespective of host association. At the same time, we identify specific genes whose presence is important for P. syringae's ability to flourish within A. thaliana. Specifically, the A. thaliana strains uniquely share a genomic island encoding toxins active against plants and surrounding microbes, suggesting a role for microbe-microbe interactions in dictating the abundance within this host. Overall, our results demonstrate that while variation in the presence of specific genes can affect the success of a pathogen within its host, the majority of gene content variation is not strongly associated with patterns of host use.
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Affiliation(s)
- Talia L. Karasov
- Committee On Genetics Genomics & Systems Biology, University of Chicago, Chicago, Illinois, United States of America
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America
| | - Luke Barrett
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America
- CSIRO Agriculture, Canberra, ACT 2601, Australia
| | - Ruth Hershberg
- Department of Genetics, the Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Joy Bergelson
- Committee On Genetics Genomics & Systems Biology, University of Chicago, Chicago, Illinois, United States of America
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America
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Choi K, Reinhard C, Serra H, Ziolkowski PA, Underwood CJ, Zhao X, Hardcastle TJ, Yelina NE, Griffin C, Jackson M, Mézard C, McVean G, Copenhaver GP, Henderson IR. Recombination Rate Heterogeneity within Arabidopsis Disease Resistance Genes. PLoS Genet 2016; 12:e1006179. [PMID: 27415776 PMCID: PMC4945094 DOI: 10.1371/journal.pgen.1006179] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 06/15/2016] [Indexed: 12/31/2022] Open
Abstract
Meiotic crossover frequency varies extensively along chromosomes and is typically concentrated in hotspots. As recombination increases genetic diversity, hotspots are predicted to occur at immunity genes, where variation may be beneficial. A major component of plant immunity is recognition of pathogen Avirulence (Avr) effectors by resistance (R) genes that encode NBS-LRR domain proteins. Therefore, we sought to test whether NBS-LRR genes would overlap with meiotic crossover hotspots using experimental genetics in Arabidopsis thaliana. NBS-LRR genes tend to physically cluster in plant genomes; for example, in Arabidopsis most are located in large clusters on the south arms of chromosomes 1 and 5. We experimentally mapped 1,439 crossovers within these clusters and observed NBS-LRR gene associated hotspots, which were also detected as historical hotspots via analysis of linkage disequilibrium. However, we also observed NBS-LRR gene coldspots, which in some cases correlate with structural heterozygosity. To study recombination at the fine-scale we used high-throughput sequencing to analyze ~1,000 crossovers within the RESISTANCE TO ALBUGO CANDIDA1 (RAC1) R gene hotspot. This revealed elevated intragenic crossovers, overlapping nucleosome-occupied exons that encode the TIR, NBS and LRR domains. The highest RAC1 recombination frequency was promoter-proximal and overlapped CTT-repeat DNA sequence motifs, which have previously been associated with plant crossover hotspots. Additionally, we show a significant influence of natural genetic variation on NBS-LRR cluster recombination rates, using crosses between Arabidopsis ecotypes. In conclusion, we show that a subset of NBS-LRR genes are strong hotspots, whereas others are coldspots. This reveals a complex recombination landscape in Arabidopsis NBS-LRR genes, which we propose results from varying coevolutionary pressures exerted by host-pathogen relationships, and is influenced by structural heterozygosity.
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Affiliation(s)
- Kyuha Choi
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Carsten Reinhard
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Heïdi Serra
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Piotr A. Ziolkowski
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
- Department of Biotechnology, Adam Mickiewicz University, Poznan, Poland
| | - Charles J. Underwood
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Xiaohui Zhao
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Thomas J. Hardcastle
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Nataliya E. Yelina
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Catherine Griffin
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Matthew Jackson
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
| | - Christine Mézard
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, Versailles, France
| | - Gil McVean
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Gregory P. Copenhaver
- Department of Biology and the Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Ian R. Henderson
- Department of Plant Sciences, Downing Street, University of Cambridge, Cambridge, United Kingdom
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Roux F, Bergelson J. The Genetics Underlying Natural Variation in the Biotic Interactions of Arabidopsis thaliana: The Challenges of Linking Evolutionary Genetics and Community Ecology. Curr Top Dev Biol 2016; 119:111-56. [PMID: 27282025 DOI: 10.1016/bs.ctdb.2016.03.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In the context of global change, predicting the responses of plant communities in an ever-changing biotic environment calls for a multipronged approach at the interface of evolutionary genetics and community ecology. However, our understanding of the genetic basis of natural variation involved in mediating biotic interactions, and associated adaptive dynamics of focal plants in their natural communities, is still in its infancy. Here, we review the genetic and molecular bases of natural variation in the response to biotic interactions (viruses, bacteria, fungi, oomycetes, herbivores, and plants) in the model plant Arabidopsis thaliana as well as the adaptive value of these bases. Among the 60 identified genes are a number that encode nucleotide-binding site leucine-rich repeat (NBS-LRR)-type proteins, consistent with early examples of plant defense genes. However, recent studies have revealed an extensive diversity in the molecular mechanisms of defense. Many types of genetic variants associate with phenotypic variation in biotic interactions, even among the genes of large effect that tend to be identified. In general, we found that (i) balancing selection rather than directional selection explains the observed patterns of genetic diversity within A. thaliana and (ii) the cost/benefit tradeoffs of adaptive alleles can be strongly dependent on both genomic and environmental contexts. Finally, because A. thaliana rarely interacts with only one biotic partner in nature, we highlight the benefit of exploring diffuse biotic interactions rather than tightly associated host-enemy pairs. This challenge would help to improve our understanding of coevolutionary quantitative genetics within the context of realistic community complexity.
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Affiliation(s)
- F Roux
- INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France; CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France.
| | - J Bergelson
- University of Chicago, Chicago, IL, United States
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MacQueen A, Bergelson J. Modulation of R-gene expression across environments. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:2093-105. [PMID: 26983577 PMCID: PMC4793800 DOI: 10.1093/jxb/erv530] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Some environments are more conducive to pathogen growth than others, and, as a consequence, plants might be expected to invest more in resistance when pathogen growth is favored. Resistance (R-) genes in Arabidopsis thaliana have unusually extensive variation in basal expression when comparing the same R-gene among accessions collected from different environments. R-gene expression variation was characterized to explore whether R-gene expression is up-regulated in environments favoring pathogen proliferation and down-regulated when risks of infection are low; down-regulation would follow if costs of R-gene expression negatively impact plant fitness in the absence of disease. Quantitative reverse transcription-PCR was used to quantify the expression of 13 R-gene loci in plants grown in eight environmental conditions for each of 12 A. thaliana accessions, and large effects of the environment on R-gene expression were found. Surprisingly, almost every change in the environment--be it a change in biotic or abiotic conditions--led to an increase in R-gene expression, a response that was distinct from the average transcriptome response and from that of other stress response genes. These changes in expression are functional in that environmental change prior to infection affected levels of specific disease resistance to isolates of Pseudomonas syringae. In addition, there are strong latitudinal clines in basal R-gene expression and clines in R-gene expression plasticity correlated with drought and high temperatures. These results suggest that variation in R-gene expression across environments may be shaped by natural selection to reduce fitness costs of R-gene expression in permissive or predictable environments.
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Affiliation(s)
- Alice MacQueen
- Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA
| | - Joy Bergelson
- Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA.
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Abstract
Darwin's theory of evolution by natural selection is the foundation of modern biology. However, it has proven remarkably difficult to demonstrate at the genetic, genomic, and population level exactly how wild species adapt to their natural environments. We discuss how one can use large sets of multiple genome sequences from wild populations to understand adaptation, with an emphasis on the small herbaceous plant Arabidopsis thaliana. We present motivation for such studies; summarize progress in describing whole-genome, species-wide sequence variation; and then discuss what insights have emerged from these resources, either based on sequence information alone or in combination with phenotypic data. We conclude with thoughts on opportunities with other plant species and the impact of expected progress in sequencing technology and genome engineering for studying adaptation in nature.
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Affiliation(s)
- Detlef Weigel
- Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany;
| | - Magnus Nordborg
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter, 1030 Vienna, Austria;
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The long-term maintenance of a resistance polymorphism through diffuse interactions. Nature 2014; 512:436-440. [PMID: 25043057 DOI: 10.1038/nature13439] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 05/01/2014] [Indexed: 11/09/2022]
Abstract
Plant resistance (R) genes are a crucial component in plant defence against pathogens. Although R genes often fail to provide durable resistance in an agricultural context, they frequently persist as long-lived balanced polymorphisms in nature. Standard theory explains the maintenance of such polymorphisms through a balance of the costs and benefits of resistance and virulence in a tightly coevolving host-pathogen pair. However, many plant-pathogen interactions lack such specificity. Whether, and how, balanced polymorphisms are maintained in diffusely interacting species is unknown. Here we identify a naturally interacting R gene and effector pair in Arabidopsis thaliana and its facultative plant pathogen, Pseudomonas syringae. The protein encoded by the R gene RPS5 recognizes an AvrPphB homologue (AvrPphB2) and exhibits a balanced polymorphism that has been maintained for over 2 million years (ref. 3). Consistent with the presence of an ancient balanced polymorphism, the R gene confers a benefit when plants are infected with P. syringae carrying avrPphB2 but also incurs a large cost in the absence of infection. RPS5 alleles are maintained at intermediate frequencies in populations globally, suggesting ubiquitous selection for resistance. However, the presence of P. syringae carrying avrPphB is probably insufficient to explain the RPS5 polymorphism. First, avrPphB homologues occur at very low frequencies in P. syringae populations on A. thaliana. Second, AvrPphB only rarely confers a virulence benefit to P. syringae on A. thaliana. Instead, we find evidence that selection for RPS5 involves multiple non-homologous effectors and multiple pathogen species. These results and an associated model suggest that the R gene polymorphism in A. thaliana may not be maintained through a tightly coupled interaction involving a single coevolved R gene and effector pair. More likely, the stable polymorphism is maintained through complex and diffuse community-wide interactions.
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Karasov TL, Horton MW, Bergelson J. Genomic variability as a driver of plant-pathogen coevolution? CURRENT OPINION IN PLANT BIOLOGY 2014; 18:24-30. [PMID: 24491596 PMCID: PMC4696489 DOI: 10.1016/j.pbi.2013.12.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 12/16/2013] [Accepted: 12/20/2013] [Indexed: 05/03/2023]
Abstract
Pathogens apply one of the strongest selective pressures in plant populations. Understanding plant-pathogen coevolution has therefore been a major research focus for at least sixty years [1]. Recent comparative genomic studies have revealed that the genes involved in plant defense and pathogen virulence are among the most polymorphic in the respective genomes. Which fraction of this diversity influences the host-pathogen interaction? Do coevolutionary dynamics maintain variation? Here we review recent literature on the evolutionary and molecular processes that shape this variation, focusing primarily on gene-for-gene interactions. In summarizing theoretical and empirical studies of the processes that shape this variation in natural plant and pathogen populations, we find a disconnect between the complexity of ecological interactions involving hosts and their myriad microbes, and the models that describe them.
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Affiliation(s)
- Talia L Karasov
- University of Chicago, Chicago, IL 60637, USA; Committee on Genetics, Genomics and Systems Biology
| | | | - Joy Bergelson
- University of Chicago, Chicago, IL 60637, USA; Department of Ecology & Evolution.
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Van der Linden L, Bredenkamp J, Naidoo S, Fouché-Weich J, Denby KJ, Genin S, Marco Y, Berger DK. Gene-for-gene tolerance to bacterial wilt in Arabidopsis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:398-406. [PMID: 23234403 DOI: 10.1094/mpmi-07-12-0188-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Bacterial wilt caused by Ralstonia solanacearum is a disease of widespread economic importance that affects numerous plant species, including Arabidopsis thaliana. We describe a pathosystem between A. thaliana and biovar 3 phylotype I strain BCCF402 of R. solanacearum isolated from Eucalyptus trees. A. thaliana accession Be-0 was susceptible and accession Kil-0 was tolerant. Kil-0 exhibited no wilting symptoms and no significant reduction in fitness (biomass, seed yield, and germination efficiency) after inoculation with R. solanacearum BCCF402, despite high bacterial numbers in planta. This was in contrast to the well-characterized resistance response in the accession Nd-1, which limits bacterial multiplication at early stages of infection and does not wilt. R. solanacearum BCCF402 was highly virulent because the susceptible accession Be-0 was completely wilted after inoculation. Genetic analyses, allelism studies with Nd-1, and RRS1 cleaved amplified polymorphic sequence marker analysis showed that the tolerance phenotype in Kil-0 was dependent upon the resistance gene RRS1. Knockout and complementation studies of the R. solanacearum BCCF402 effector PopP2 confirmed that the tolerance response in Kil-0 was dependent upon the RRS1-PopP2 interaction. Our data indicate that the gene-for-gene interaction between RRS1 and PopP2 can contribute to tolerance, as well as resistance, which makes it a useful model system for evolutionary studies of the arms race between plants and bacterial pathogens. In addition, the results alert biotechnologists to the risk that deployment of RRS1 in transgenic crops may result in persistence of the pathogen in the field.
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Affiliation(s)
- Liesl Van der Linden
- Department of Plant Science, Forestry and Agricultural Research Institute, South Africa
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Salvaudon L, Shykoff JA. Variation in Arabidopsis developmental responses to oomycete infection: resilience vs changes in life history traits. THE NEW PHYTOLOGIST 2013; 197:919-926. [PMID: 23231447 DOI: 10.1111/nph.12073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 10/23/2012] [Indexed: 06/01/2023]
Abstract
Although plant resistance to aggressors has been well described, there is still little knowledge about the mechanisms underlying their tolerance to pathogens. Tolerance often appears to be mediated by changes in life history traits, shifting host resource investment from growth to reproduction, but whether host phenotype modifications induced after attack are adaptive is not always clear. Here, we investigated the details of the impact of Hyaloperonospora arabidopsidis infection on several biomass, phenology and architectural traits of Arabidopsis thaliana, for three pathogen genotypes and three host plant genotypes that have been shown previously to differ greatly in fecundity and tolerance to infection. We found that, although host genotype explains most of the variance in life history traits, these three lines differ critically in their response to infection, with delays and biomass losses at bolting, together with changes in inflorescence architecture, observed at one extreme host line, and an advantage at bolting for infected plants and no inflorescence alteration for the other. These results suggest that the differences in tolerance observed previously in this pathosystem do not involve plasticity in inflorescence architecture, but may arise from induced changes at the vegetative stage, before plant transition to reproduction.
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Affiliation(s)
- Lucie Salvaudon
- Univ Paris-Sud, Laboratoire Ecologie Systématique et Evolution, UMR 8079, F 91405 Orsay, France
- CNRS, UMR 8079, F-91405 Orsay, France
- AgroParisTech, UMR 8079, F-91405 Orsay, France
| | - Jacqui A Shykoff
- Univ Paris-Sud, Laboratoire Ecologie Systématique et Evolution, UMR 8079, F 91405 Orsay, France
- CNRS, UMR 8079, F-91405 Orsay, France
- AgroParisTech, UMR 8079, F-91405 Orsay, France
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12
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Bergelson J, Roux F. Towards identifying genes underlying ecologically relevant traits in Arabidopsis thaliana. Nat Rev Genet 2010; 11:867-79. [PMID: 21085205 DOI: 10.1038/nrg2896] [Citation(s) in RCA: 210] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A major challenge in evolutionary biology and plant breeding is to identify the genetic basis of complex quantitative traits, including those that contribute to adaptive variation. Here we review the development of new methods and resources to fine-map intraspecific genetic variation that underlies natural phenotypic variation in plants. In particular, the analysis of 107 quantitative traits reported in the first genome-wide association mapping study in Arabidopsis thaliana sets the stage for an exciting time in our understanding of plant adaptation. We also argue for the need to place phenotype-genotype association studies in an ecological context if one is to predict the evolutionary trajectories of plant species.
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Affiliation(s)
- Joy Bergelson
- Department of Ecology and Evolution, University of Chicago, Illinois 60637, USA.
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13
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Kniskern JM, Barrett LG, Bergelson J. Maladaptation in wild populations of the generalist plant pathogen Pseudomonas syringae. Evolution 2010; 65:818-30. [PMID: 21044058 DOI: 10.1111/j.1558-5646.2010.01157.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Multihost pathogens occur widely on both natural and agriculturally managed hosts. Despite the importance of such generalists, evolutionary studies of host-pathogen interactions have largely focused on tightly coupled interactions between species pairs. We characterized resistance in a collection of Arabidopsis thaliana hosts, including 24 accessions collected from the Midwest USA and 24 from around the world, and patterns of virulence in a collection of Pseudomonas syringae strains, including 24 strains collected from wild Midwest populations of A. thaliana (residents) and 18 from an array of cultivated species (nonresidents). All of the nonresident strains and half of the resident strains elicited a resistance response on one or more A. thaliana accessions. The resident strains that failed to elicit any resistance response possessed an alternative type III secretion system (T3SS) that is unable to deliver effectors into plant host cells; as a result, these seemingly nonpathogenic strains are incapable of engaging in gene for gene interactions with A. thaliana. The remaining resident strains triggered greater resistance compared to nonresident strains, consistent with maladaptation of the resident bacterial population. We weigh the plausibility of two explanations: general maladaptation of pathogen strains and a more novel hypothesis whereby community level epidemiological dynamics result in adaptive dynamics favoring ephemeral hosts like A. thaliana.
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Affiliation(s)
- Joel M Kniskern
- Department of Ecology and Evolution, University of Chicago, 1101 E. 57th Street, Chicago, Illinois 60637, USA
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14
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Impact of initial pathogen density on resistance and tolerance in a polymorphic disease resistance gene system in Arabidopsis thaliana. Genetics 2010; 185:283-91. [PMID: 20142437 DOI: 10.1534/genetics.109.112383] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The evolution of natural enemy defense shapes evolutionary trajectories of natural populations. Although the intensity of selection imposed by enemies clearly varies among natural populations, little is known about the reaction norm of genotypes under a gradient of selective pressure. In this study, we measure the quantitative responses of disease symptoms and plant fitness to a gradient of infection, focusing on the gene-for-gene interaction between the Rpm1 resistance gene in Arabidopsis thaliana and the AvrRpm1 avirulence gene in the bacterial pathogen Pseudomonas syringae. Two complementary sets of plant material were used: resistant (R) and susceptible (S) isogenic lines and a set of six natural accessions, three of which are Rpm1 resistant (R) and three of which are rpm1 susceptible (S). Nine initial pathogen densities were applied to each plant line. Using isogenic lines allows any differences between R and S lines to be attributed directly to the Rpm1 gene, whereas using natural accessions allows the natural variation of resistance and tolerance over a gradient of infection dosages within R and S accessions to be described. For both sets of plant material, increased infection dosage results in more extensive disease symptoms, with a subsequent decrease in seed production. The severity of disease symptoms was reduced in R relative to S subgroups, and the presence of the Rpm1 allele led to an increase in plant fitness. Tolerance, defined as the ability to sustain infection without a reduction in fitness, was directly affected by Rpm1, providing a novel demonstration of an R gene affecting tolerance. Genetic variation for tolerance was also found within the S and R natural accessions, suggesting the potential for selection to act upon this important trait.
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