Suchergebnisse

18 páginas, 7 figuras, 2 tablas ; Studies on plant-mediated interactions between root parasitic nematodes and aboveground herbivores are rapidly increasing. However, the outcomes for the interacting organisms vary, and the mechanisms involved remain ambiguous. We hypothesized that the impact of root infection by the root-knot nematode Meloidogyne incognita on the performance of the aboveground caterpillar Spodoptera exigua is modulated by the nematode's infection cycle. We challenged root-knot nematode infected tomato plants with caterpillars when the nematode's infection cycle was either at the invasion, galling, or reproduction stage. We found that M. incognita root infection enhanced S. exigua performance during the galling stage, while it did not affect the caterpilar's performance at the invasion and reproduction stages. Molecular and chemical analyses performed at the different stages of the nematode infection cycle revealed that M. incognita root infection systemically affected the jasmonic acid-, salicylic acid- and abscisic acid-related responses, as well as changes in the leaf metabolome during S. exigua feeding. The M. incognita induced leaf responses significantly varied over the nematode's root infection cycle. These findings suggest that specific leaf responses triggered systemically by the nematode at its different life-cycle stages underlie the differential impact of M. incognita on plant resistance against the caterpillar S. exigua. ; All authors gratefully acknowledge the support of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig funded by the German Research Foundation (DFG-FZT 118, 202548816). CMM acknowledges the Deutscher Akademischer Austauschdienst (DAAD) for a doctoral research grant (research grant No: 91607343). AMM acknowledges funding from the program for attracting talent to Salamanca from the Fundación Salamanca Ciudad de Cultura y Saberes and Ayuntamiento de Salamanca; the program to support junior researchers to obtain thirdparty funding from Friedrich-Schiller-Universitat Jena (DRM/2015-02); Junta de Castilla y León and European Union (ERDF "Europe drives our growth"; CLU-2019-05 - IRNASA/ CSIC Unit of Excellence); and the research network RED2018-102407-T from the Spanish Ministry of Science and Innovation and Feder funds ; Peer reviewed

17 páginas, 8 figuras ; Shoot herbivores may influence the communities of herbivores associated with the roots via inducible defenses. However, the molecular mechanisms and hormonal signaling underpinning the systemic impact of leaf herbivory on root-induced responses against nematodes remain poorly understood. By using tomato (Solanum lycopersicum) as a model plant, we explored the impact of leaf herbivory by Manduca sexta on the performance of the root knot nematode Meloidogyne incognita. By performing glasshouse bioassays, we found that leaf herbivory reduced M. incognita performance in the roots. By analyzing the root expression profile of a set of oxylipin-related marker genes and jasmonate root content, we show that leaf herbivory systemically activates the 13-Lipoxigenase (LOX) and 9-LOX branches of the oxylipin pathway in roots and counteracts the M. incognita-triggered repression of the 13-LOX branch. By using untargeted metabolomics, we also found that leaf herbivory counteracts the M. incognita-mediated repression of putative root chemical defenses. To explore the signaling involved in this shoot-to-root interaction, we performed glasshouse bioassays with grafted plants compromised in jasmonate synthesis or perception, specifically in their shoots. We demonstrated the importance of an intact shoot jasmonate perception, whereas having an intact jasmonate biosynthesis pathway was not essential for this shoot-to-root interaction. Our results highlight the impact of leaf herbivory on the ability of M. incognita to manipulate root defenses and point to an important role for the jasmonate signaling pathway in shoot-to-root signaling. ; This research was supported by the German Research Foundation (DFG–FZT 118, 202548816), by the program for attracting talent to Salamanca from Fundacio´n Salamanca Ciudad de Cultura y Saberes and Ayuntamiento de Salamanca (to A.M.M.), by the program to support junior researchers to obtain third-party funding from FriedrichSchiller-Universita¨t Jena (DRM/2015-02, to A.M.M.) y the Deutscher Akademischer Austauschdienst (DAAD 91607343, to C.M.M); by Junta de Castilla y León and European Union (ERDF "Europe drives our growth"; CLU-2019-05 – IRNASA/CSIC Unit of Excellence); and the research network RED2018-102407-T from the Spanish Ministry of Science and Innovation and Feder funds. ; Peer reviewed

11 páginas, 4 figuras y 3 tablas. ; Plants form mutualistic relationship with a variety of belowground fungal species. Such a mutualistic relationship can enhance plant growth and resistance to pathogens. Yet, we know little about how interactions between functionally diverse groups of fungal mutualists affect plant performance and competition. We experimentally determined the effects of interaction between two functional groups of belowground fungi that form mutualistic relationship with plants, arbuscular mycorrhizal (AM) fungi and Trichoderma, on interspecific competition between pairs of closely related plant species from four different genera. We hypothesized that the combination of two functionally diverse belowground fungal species would allow plants and fungi to partition their symbiotic relationships and relax plant–plant competition. Our results show that: 1) the AM fungal species consistently outcompeted the Trichoderma species independent of plant combinations; 2) the fungal species generally had limited effects on competitive interactions between plants; 3) however, the combination of fungal species relaxed interspecific competition in one of the four instances of plant–plant competition, despite the general competitive superiority of AM fungi over Trichoderma. We highlight that the competitive outcome between functionally diverse fungal species may show high consistency across a broad range of host plants and their combinations. However, despite this consistent competitive hierarchy, the consequences of their interaction for plant performance and competition can strongly vary among plant communities. ; MPT acknowledges funding from the German Research Foundation (DFG, TH 2307/1‐1). This project has received funding from the European Union's Horizon 2020 research and Innovation programme under grant agreement No 765290. AMM, NMvD and AB further acknowledge the COST Action FA1405. AM acknowledges funding from the program for attracting talent to Salamanca from Fundación Salamanca Ciudad de Cultura y Saberes. Further support came from the German Centre for Integrative Biodiversity Research Halle–Jena–Leipzig, funded by the German Research Foundation (FZT 118). Author contributions ‐ MPT conceived the idea. MPT, NvD, NE, CR and AM‐M developed the ideas for the experiment. VQ, MPT and AM‐M performed the experiment. MPT analyzed the data and wrote the first draft of the manuscript. All authors contributed to manuscript revisions. ; Peer reviewed

23 páginas, 6 figuras, 5 tablas ; Root mutualistic microbes can modulate the production of plant secondary metabolites affecting plant–herbivore interactions. Still, the main mechanisms underlying the impact of root mutualists on herbivore performance remain ambiguous. In particular, little is known about how changes in the plant metabolome induced by root mutualists affect the insect metabolome and postlarval development. By using bioassays with tomato plants (Solanum lycopersicum), we analyzed the impact of the arbuscular mycorrhizal fungus Rhizophagus irregularis and the growth-promoting fungus Trichoderma harzianum on the plant interaction with the specialist insect herbivore Manduca sexta. We found that root colonization by the mutualistic microbes impaired insect development, including metamorphosis. By using untargeted metabolomics, we found that root colonization by the mutualistic microbes altered the secondary metabolism of tomato shoots, leading to enhanced levels of steroidal glycoalkaloids. Untargeted metabolomics further revealed that root colonization by the mutualists affected the metabolome of the herbivore, leading to an enhanced accumulation of steroidal glycoalkaloids and altered patterns of fatty acid amides and carnitine-derived metabolites. Our results indicate that the changes in the shoot metabolome triggered by root mutualistic microbes can cascade up altering the metabolome of the insects feeding on the colonized plants, thus affecting the insect development. ; The work of D.P. was supported by the European Union's Horizon 2020 research and innovation program (Microbe-Induced Resistance, MiRA project), grant agreement no. 765290. D.P., F.V., A.W., N.M.v.D. and A.M.-M. gratefully acknowledge the support of iDiv funded by the German Research Foundation (DFG–FZT 118, 202548816). A.M.-M. acknowledges funding from the program for attracting talent to Salamanca from the Fundación Salamanca Ciudad de Cultura y Saberes and Ayuntamiento de Salamanca; the program to support junior researchers to obtain third-party funding from Friedrich-Schiller-Universität Jena (DRM/2015-02); Junta de Castilla y León and European Union (ERDF "Europe drives our growth"; CLU-2019-05—IRNASA /CSIC Unit of Excellence); and the research network RED2018-102407-T from the Spanish Ministry of Science and Innovation and Feder funds. ; Peer reviewed

14 páginas, 3 figuras, 2 tablas ; Research aimed at understanding the mechanisms underlying the relationship between tree diversity and antagonist infestation is often neglecting resource-use complementarity among plant species. We investigated the effects of tree species identity, species richness, and mycorrhizal type on leaf herbivory and pathogen infestation. We used a tree sapling experiment manipulating the two most common mycorrhizal types, arbuscular mycorrhiza and ectomycorrhiza, via respective tree species in monocultures and two-species mixtures. We visually assessed leaf herbivory and pathogen infestation rates, and measured concentrations of a suite of plant metabolites (amino acids, sugars, and phenolics), leaf elemental concentrations (carbon, nitrogen, and phosphorus), and tree biomass. Tree species and mycorrhizal richness had no significant effect on herbivory and pathogen infestation, whereas species identity and mycorrhizal type had. Damage rates were higher in arbuscular mycorrhizal (AM) than in ectomycorrhizal (EM) trees. Our structural equation model (SEM) indicated that elemental, but not metabolite concentrations, determined herbivory and pathogen infestation, suggesting that the investigated chemical defence strategies may not have been involved in the effects found in our study with tree saplings. Other chemical and physical defence strategies as well as species identity as its determinant may have played a more crucial role in the studied saplings. Furthermore, the SEM indicated a direct positive effect of AM trees on herbivory rates, suggesting that other dominant mechanisms, not considered here, were involved as well. We found differences in the attribution of elemental concentrations between the two rates. This points to the fact that herbivory and pathogen infestation are driven by distinct mechanisms. Our study highlights the importance of biotic contexts for understanding the mechanisms underlying the effects of biodiversity on tree-antagonist interactions. ; We thank Nicole M. van Dam, Henriette Uthe, Fredd Vergara, Martin Volf, and Alexander Weinhold for their valuable advice on metabolite analyses as well as Beate Rothe and Michael Reichelt for their help with chemical analyses. Moreover, comments by two anonymous reviewers helped to improve the paper. This work was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 677232). Further support came from the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig and the EcoMetEoR platform, funded by the German Research Foundation (FZT 118). AMM acknowledges support from the program for attracting talent to Salamanca from Fundación Salamanca Ciudad de Cultura y Saberes and Ayuntamiento de Salamanca. ; Peer reviewed