As primary producers, plants are under constant pressure to defend themselves against potentially deadly pathogens and herbivores. In this review, we describe short- and long-term strategies that ...enable plants to cope with these stresses. Apart from internal immunological strategies that involve physiological and (epi)genetic modifications at the cellular level, plants also employ external strategies that rely on recruitment of beneficial organisms. We discuss these strategies along a gradient of increasing timescales, ranging from rapid immune responses that are initiated within seconds to (epi)genetic adaptations that occur over multiple plant generations. We cover the latest insights into the mechanistic and evolutionary underpinnings of these strategies and present explanatory models. Finally, we discuss how knowledge from short-lived model species can be translated to economically and ecologically important perennials to exploit adaptive plant strategies and mitigate future impacts of pests and diseases in an increasingly interconnected and changing world.
Arbuscular mycorrhizal (AM) fungi are amongst the most common and functionally important symbionts of terrestrial plants and are highly likely to be affected by global change. The potential ...consequences of this on plant growth and carbon and nutrient cycling has led to a growing demand for their inclusion in global change models. However, our understanding of their responses to environmental change remains limited. This review provides an overview of recent experiments attempting to predict the effects of atmospheric and climatic change on AM fungal community diversity, composition and functioning. This includes rising atmospheric carbon dioxide and tropospheric ozone levels, altered water availability, warming and nitrogen deposition. Changes detected are often highly variable and context dependent, but trends are emerging such as the similar responses of community composition to enhanced nitrogen deposition and atmospheric CO2, despite the likely contrasting effects of these environmental changes on carbon availability. The review also highlights shortfalls in our current knowledge and suggests priorities for future research, particularly advocating more integrated approaches linking the study of community characteristics and functions and examination of fine level genetic changes, wider geographical contexts and a greater range of AM fungal functions.
The rhizobiome is an important regulator of plant growth and health. Plants shape their rhizobiome communities through production and release of primary and secondary root metabolites. Benzoxazinoids ...(BXs) are common tryptophan-derived secondary metabolites in grasses that regulate belowground and aboveground biotic interactions. In addition to their biocidal activity, BXs can regulate plant-biotic interactions as semiochemicals or within-plant defence signals. However, the full extent and mechanisms by which BXs shape the root-associated microbiome has remained largely unexplored. Here, we have taken a global approach to examine the regulatory activity of BXs on the maize root metabolome and associated bacterial and fungal communities. Using untargeted mass spectrometry analysis in combination with prokaryotic and fungal amplicon sequencing, we compared the impacts of three genetic mutations in different steps in the BX pathway. We show that BXs regulate global root metabolism and concurrently influence the rhizobiome in a root type-dependent manner. Correlation analysis between BX-controlled root metabolites and bacterial taxa suggested a dominant role for BX-dependent metabolites, particularly flavonoids, in constraining a range of soil microbial taxa, while stimulating methylophilic bacteria. Our study supports a multilateral model by which BXs control root-microbe interactions via a global regulatory function in root secondary metabolism.
Lost in diversity Mommer, Liesje; Cotton, T. E. Anne; Raaijmakers, Jos M. ...
The New phytologist,
April 2018, Letnik:
218, Številka:
2
Journal Article
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There is consensus that plant species richness enhances plant productivity within natural grasslands, but the underlying drivers remain debated. Recently, differential accumulation of soil-borne ...fungal pathogens across the plant diversity gradient has been proposed as a cause of this pattern. However, the below-ground environment has generally been treated as a ‘black box’ in biodiversity experiments, leaving these fungi unidentified.
Using next generation sequencing and pathogenicity assays, we analysed the community composition of root-associated fungi from a biodiversity experiment to examine if evidence exists for host specificity and negative density dependence in the interplay between soil-borne fungi, plant diversity and productivity.
Plant species were colonised by distinct (pathogenic) fungal communities and isolated fungal species showed negative, species-specific effects on plant growth. Moreover, 57% of the pathogenic fungal operational taxonomic units (OTUs) recorded in plant monocultures were not detected in eight plant species plots, suggesting a loss of pathogenic OTUs with plant diversity.
Our work provides strong evidence for host specificity and negative density-dependent effects of root-associated fungi on plant species in grasslands. Our work substantiates the hypothesis that fungal root pathogens are an important driver of biodiversity-ecosystem functioning relationships.
Metabolite profiling of non‐sterile rhizosphere soil Pétriacq, Pierre; Williams, Alex; Cotton, Anne ...
The Plant journal : for cell and molecular biology,
October 2017, Letnik:
92, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Summary
Rhizosphere chemistry is the sum of root exudation chemicals, their breakdown products and the microbial products of soil‐derived chemicals. To date, most studies about root exudation ...chemistry are based on sterile cultivation systems, which limits the discovery of microbial breakdown products that act as semiochemicals and shape microbial rhizosphere communities. Here, we present a method for untargeted metabolic profiling of non‐sterile rhizosphere soil. We have developed an experimental growth system that enables the collection and analysis of rhizosphere chemicals from different plant species. High‐throughput sequencing of 16SrRNA genes demonstrated that plants in the growth system support a microbial rhizosphere effect. To collect a range of (a)polar chemicals from the system, we developed extraction methods that do not cause detectable damage to root cells or soil‐inhabiting microbes, thus preventing contamination with cellular metabolites. Untargeted metabolite profiling by UPLC‐Q‐TOF mass spectrometry, followed by uni‐ and multivariate statistical analyses, identified a wide range of secondary metabolites that are enriched in plant‐containing soil, compared with control soil without roots. We show that the method is suitable for profiling the rhizosphere chemistry of Zea mays (maize) in agricultural soil, thereby demonstrating the applicability to different plant–soil combinations. Our study provides a robust method for the comprehensive metabolite profiling of non‐sterile rhizosphere soil, which represents a technical advance towards the establishment of causal relationships between the chemistry and microbial composition of the rhizosphere.
Significance Statement
Multitrophic interactions in the rhizosphere are critical for plant growth and health, and are influenced by root exudates and their microbial breakdown products. In this study, we describe a straightforward method for metabolic profiling of non‐sterile rhizosphere soil, which represents an efficient technique to identify novel semiochemicals that shape the microbial community structure and activity of the rhizosphere.
The composition and structure of plant-root-associated fungal communities are determined by local abiotic and biotic conditions. However, the relative influence and identity of relationships to ...abiotic and biotic factors may differ across environmental and ecological contexts, and fungal functional groups. Thus, understanding which aspects of root-associated fungal community ecology generalise across contexts is the first step towards a more predictive framework. We investigated how the relative importance of biotic and abiotic factors scale across environmental and ecological contexts using high-throughput sequencing (ca. 55 M Illumina metabarcoding sequences) of >260 plant-root-associated fungal communities from six UK salt marshes across two geographic regions (South-East and North-West England) in winter and summer. Levels of root-associated fungal diversity were comparable with forests and temperate grasslands, quadrupling previous estimates of salt-marsh fungal diversity. Whilst abiotic variables were generally most important, a range of site- and spatial scale-specific abiotic and biotic drivers of diversity and community composition were observed. Consequently, predictive models of diversity trained on one site, extrapolated poorly to others. Fungal taxa from the same functional groups responded similarly to the specific drivers of diversity and composition. Thus site, spatial scale and functional group are key factors that, if accounted for, may lead to a more predictive understanding of fungal community ecology.
Understanding the natural dynamics of arbuscular mycorrhizal (AM) fungi and their response to global environmental change is essential for the prediction of future plant growth and ecosystem ...functions. We investigated the long‐term temporal dynamics and effect of elevated atmospheric carbon dioxide (CO₂) and ozone (O₃) concentrations on AM fungal communities. Molecular methods were used to characterize the AM fungal communities of soybean (Glycine max) grown under elevated and ambient atmospheric concentrations of both CO₂and O₃within a free air concentration enrichment experiment in three growing seasons over 5 yr. Elevated CO₂altered the community composition of AM fungi, increasing the ratio of Glomeraceae to Gigasporaceae. By contrast, no effect of elevated O₃on AM fungal communities was detected. However, the greatest compositional differences detected were between years, suggesting that, at least in the short term, large‐scale interannual temporal dynamics are stronger mediators than atmospheric CO₂concentrations of AM fungal communities. We conclude that, although atmospheric change may significantly alter AM fungal communities, this effect may be masked by the influences of natural changes and successional patterns through time. We suggest that changes in carbon availability are important determinants of the community dynamics of AM fungi.
PurposeThe European External Action Service (EEAS) is a relatively new diplomatic service established in 2010. In previous analyses, the authors noted a dominance of security and foreign policy ...messages emanating from the EEAS, demonstrating the European Union (EU)'s negotiating power. It was clear it had discovered the benefits of public diplomacy, but rather practised traditional diplomacy on public diplomacy specific platforms. The authors aim to pursue the monitoring of the EEAS’ strategy, covering 2019 and 2020, to understand how the use of Twitter supports the evolution of the EU foreign policy.Design/methodology/approachQuestioning if the EEAS is entering the second phase of its life cycle (launched in 2010, its introduction phase was under Katherine Ashton, 2009–2014, followed by Federica Mogherini, 2014–2019, and Josep Borrell, 2019–2024), the authors carried out a content analysis on 765 tweets. The authors used the MARPE Diplo methodological framework to compare how the EU uses public diplomacy through its EEAS to negotiate its own interests with non-EU parties under the presidency of Federica Mogherini (period 1), during the transition period (period 2) and under the presidency of Joseph Borrell (period 3).FindingsBased on the comparison with their previous studies, the authors demonstrate that, over the years, the overall discourse of the EEAS is much more oriented towards public diplomacy.Research limitations/implicationsThe present study has two limitations. The first refers to the sampling of the participants involved in the citizen science experiment: they belong to a homogeneous age category and similar education level which might have biased their analysis. Second, the authors acknowledge the usual limitations linked to citizen science. However, the authors acknowledge a growing emphasis on the outcomes for society involving citizens and including partnerships between the public and scientists as well as an increased public engagement in policy processes.Practical implicationsThe research leads into new insights regarding the European-centred translation of the EEAS messages, compared to the off-centred view of non-European contributors.Social implicationsThe citizen science approach allows to integrate the targeted public to apply public diplomacy content analysis.Originality/valueThis case study is based on the principles of citizen science and demonstrates the importance of an off-centred approach in the analysis of the practices of public diplomacy.
Farmland birds are among the most threatened bird species in Europe, largely as a result of agricultural intensification which has driven widespread biodiversity losses. Breeding waders associated ...with grassland and arable habitats are particularly vulnerable and a frequent focus of agri‐environment schemes (AES) designed to halt and reverse population declines. We review existing literature, providing a quantitative assessment of the effectiveness of policy and management interventions used throughout Europe to improve population and demographic metrics of grassland‐breeding waders. Targeted AES and site protection measures were more likely to be effective than less targeted AES and were ten times more likely to be effective than would be expected by chance, particularly for population trend and productivity metrics. Positive effects of AES and site protection did not appear synergistic. Management interventions which had the greatest chance of increasing population growth or productivity included modification of mowing regimes, increasing wet conditions, and the use of nest protection. Success rates varied according to the species and metric being evaluated. None of the policy or management interventions we evaluated were associated with a significant risk of negative impacts on breeding waders. Our findings support the use of agri‐environment schemes, site protection, and management measures for grassland‐breeding wader conservation in Europe. Due to publication bias, our findings are most applicable to intensively managed agricultural landscapes. More studies are needed to identify measures that increase chick survival. Despite broadly effective conservation measures already in use, grassland‐breeding waders in Europe continue to decline. More research is needed to improve the likelihood and magnitude of positive outcomes, coupled with wider implementation of effective measures to substantially increase favorable land management for these species.
Our findings support the use of agri‐environment schemes, site protection, and conservation management measures such as grassland, wet feature, and predation management for grassland‐breeding wader conservation in Europe. Despite broadly effective conservation measures already in use, grassland‐breeding waders in Europe continue to decline. To reverse declines, wider implementation of effective measures is needed to substantially increase the amount of land managed favorably for these species.
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