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Schott J, Rakei J, Remus-Emsermann M, Johnston P, Mbedi S, Sparmann S, Hilker M, Paniagua Voirol LR. Microbial associates of the elm leaf beetle: uncovering the absence of resident bacteria and the influence of fungi on insect performance. Appl Environ Microbiol 2024; 90:e0105723. [PMID: 38179921 PMCID: PMC10807431 DOI: 10.1128/aem.01057-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Accepted: 10/31/2023] [Indexed: 01/06/2024] Open
Abstract
Microbial symbionts play crucial roles in the biology of many insects. While bacteria have been the primary focus of research on insect-microbe symbiosis, recent studies suggest that fungal symbionts may be just as important. The elm leaf beetle (ELB, Xanthogaleruca luteola) is a serious pest species of field elm (Ulmus minor). Using culture-dependent and independent methods, we investigated the abundance and species richness of bacteria and fungi throughout various ELB life stages and generations, while concurrently analyzing microbial communities on elm leaves. No persistent bacterial community was found to be associated with the ELB or elm leaves. By contrast, fungi were persistently present in the beetle's feeding life stages and on elm leaves. Fungal community sequencing revealed a predominance of the genera Penicillium and Aspergillus in insects and on leaves. Culture-dependent surveys showed a high prevalence of two fungal colony morphotypes closely related to Penicillium lanosocoeruleum and Aspergillus flavus. Among these, the Penicillium morphotype was significantly more abundant on feeding-damaged compared with intact leaves, suggesting that the fungus thrives in the presence of the ELB. We assessed whether the detected prevalent fungal morphotypes influenced ELB's performance by rearing insects on (i) surface-sterilized leaves, (ii) leaves inoculated with Penicillium spores, and (iii) leaves inoculated with Aspergillus spores. Insects feeding on Penicillium-inoculated leaves gained more biomass and tended to lay larger egg clutches than those consuming surface-sterilized leaves or Aspergillus-inoculated leaves. Our results demonstrate that the ELB does not harbor resident bacteria and that it might benefit from associating with Penicillium fungi.IMPORTANCEOur study provides insights into the still understudied role of microbial symbionts in the biology of the elm leaf beetle (ELB), a major pest of elms. Contrary to expectations, we found no persistent bacterial symbionts associated with the ELB or elm leaves. Our research thus contributes to the growing body of knowledge that not all insects rely on bacterial symbionts. While no persistent bacterial symbionts were detectable in the ELB and elm leaf samples, our analyses revealed the persistent presence of fungi, particularly Penicillium and Aspergillus on both elm leaves and in the feeding ELB stages. Moreover, when ELB were fed with fungus-treated elm leaves, we detected a potentially beneficial effect of Penicillium on the ELB's development and fecundity. Our results highlight the significance of fungal symbionts in the biology of this insect.
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Affiliation(s)
- Johanna Schott
- Applied Zoology/Animal Ecology, Institute of Biology, Freie Universitaet Berlin, Berlin, Germany
| | - Juliette Rakei
- Applied Zoology/Animal Ecology, Institute of Biology, Freie Universitaet Berlin, Berlin, Germany
| | | | - Paul Johnston
- Berlin Center for Genomics in Biodiversity Research (BeGenDiv), Berlin, Germany
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
| | - Susan Mbedi
- Berlin Center for Genomics in Biodiversity Research (BeGenDiv), Berlin, Germany
- Museum für Naturkunde Leibniz-Institute for Evolution and Biodiversity Science, Berlin, Germany
| | - Sarah Sparmann
- Berlin Center for Genomics in Biodiversity Research (BeGenDiv), Berlin, Germany
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
| | - Monika Hilker
- Applied Zoology/Animal Ecology, Institute of Biology, Freie Universitaet Berlin, Berlin, Germany
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Lortzing V, Valsamakis G, Jantzen F, Hundacker J, Paniagua Voirol LR, Schumacher F, Kleuser B, Hilker M. Plant defensive responses to insect eggs are inducible by general egg-associated elicitors. Sci Rep 2024; 14:1076. [PMID: 38212511 PMCID: PMC10784483 DOI: 10.1038/s41598-024-51565-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 01/06/2024] [Indexed: 01/13/2024] Open
Abstract
Egg deposition by herbivorous insects is well known to elicit defensive plant responses. Our study aimed to elucidate the insect and plant species specificity of these responses. To study the insect species specificity, we treated Arabidopsis thaliana with egg extracts and egg-associated secretions of a sawfly (Diprion pini), a beetle (Xanthogaleruca luteola) and a butterfly (Pieris brassicae). All egg extracts elicited salicylic acid (SA) accumulation in the plant, and all secretions induced expression of plant genes known to be responsive to the butterfly eggs, among them Pathogenesis-Related (PR) genes. All secretions contained phosphatidylcholine derivatives, known elicitors of SA accumulation and PR gene expression in Arabidopsis. The sawfly egg extract did not induce plant camalexin levels, while the other extracts did. Our studies on the plant species specificity revealed that Solanum dulcamara and Ulmus minor responded with SA accumulation and cell death to P. brassicae eggs, i.e. responses also known for A. thaliana. However, the butterfly eggs induced neoplasms only in S. dulcamara. Our results provide evidence for general, phosphatidylcholine-based, egg-associated elicitors of plant responses and for conserved plant core responses to eggs, but also point to plant and insect species-specific traits in plant-insect egg interactions.
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Affiliation(s)
- Vivien Lortzing
- Applied Zoology/Animal Ecology, Institute of Biology, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Haderslebener Str. 9, 12163, Berlin, Germany
| | - Georgios Valsamakis
- Applied Zoology/Animal Ecology, Institute of Biology, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Haderslebener Str. 9, 12163, Berlin, Germany
| | - Friederike Jantzen
- Applied Zoology/Animal Ecology, Institute of Biology, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Haderslebener Str. 9, 12163, Berlin, Germany
| | - Janik Hundacker
- Applied Zoology/Animal Ecology, Institute of Biology, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Haderslebener Str. 9, 12163, Berlin, Germany
| | - Luis R Paniagua Voirol
- Applied Zoology/Animal Ecology, Institute of Biology, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Haderslebener Str. 9, 12163, Berlin, Germany
- Microbiology, Institute of Biology, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Königin-Luise-Str. 12-16, 14195, Berlin, Germany
| | - Fabian Schumacher
- Pharmacology and Toxicology, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2-4, 14195, Berlin, Germany
- Core-Facility BioSupraMol, PharmaMS Subunit, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2-4, 14195, Berlin, Germany
| | - Burkhard Kleuser
- Pharmacology and Toxicology, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2-4, 14195, Berlin, Germany
| | - Monika Hilker
- Applied Zoology/Animal Ecology, Institute of Biology, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Haderslebener Str. 9, 12163, Berlin, Germany.
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