Periodic Reporting for period 4 - SYMBeetle (Symbiont-assisted cuticle biosynthesis as a key innovation contributing to the evolutionary success of beetles)
Okres sprawozdawczy: 2022-08-01 do 2024-01-31
To elucidate the key adaptations underlying evolutionary success remains one of the central challenges in evolution and ecology. However, rigorous experimental tests are usually hampered by the lack of replicate evolutionary events or the inability to manipulate a candidate trait of importance. SYMBeetle exploits the naturally replicated evolution of an experimentally tractable, symbiont-assisted key adaptation in beetles to understand its impact on niche expansion and diversification. Recent evidence indicates that beetles across at least seven different families associate with microbial symbionts that provision their host with tyrosine, an aromatic amino acid necessary for cuticle biosynthesis, hardening, and tanning. SYMBeetle addresses the hypothesis that the acquisition of tyrosine-supplementing microbes constituted a key innovation across phylogenetically distinct beetles that allowed them to expand into novel ecological niches, by relaxing the dependence on nitrogen-rich diets for successful formation of the rigid exoskeleton and protective front wings. Specifically, tyrosine supplementation may facilitate the transition to herbivory and allow for subsisting at very low ambient humidity, by facilitating the production of a thick cuticular barrier to desiccation. To test this, SYMBeetle will uniquely combine experimental manipulation of symbiotic associations to assess the symbionts’ contribution to cuticle biosynthesis and its fitness consequences (desiccation resistance and defense) with large-scale comparative approaches aimed at elucidating the taxonomic distribution, ecological contexts, and evolutionary origins of cuticle-supplementing symbioses. The results are expected to transform our understanding of microbes as important facilitators for the evolution of herbivory and the colonization of dry habitats in beetles, two factors of major relevance for the emergence of economically relevant insect pests of agricultural crops and stored products.
While the impact of intracellular symbionts on cuticle biosynthesis, sclerotization, and melanization had been previously characterized in Oryzaephilus surinamensis and its implications for desiccation resistance uncovered, nothing was known about the relevance of the symbiosis for competition or defense against natural enemies. Combining symbiont manipulation with targeted bioassays, we demonstrated that the symbionts accelerate the host’s cuticle development after metamorphosis, allowing it to escape more rapidly than aposymbiotic individuals from the period where they are especially vulnerable to predation and infection by entomopathogenic fungi (Kanyile et al. 2022).
Another selective pressure herbivorous insects experience in nature are natural and human-made toxins. Glyphosate is a widely used herbicide that targets the shikimate pathway of plants and many microbes, but its impact on nutritional endosymbionts in insects remained poorly understood. In O. surinamensis, we found that glyphosate inhibits symbiont establishment during host development and abolishes the mutualistic benefit on cuticle synthesis in adults, which could be partially rescued by dietary tyrosine supplementation (Kiefer et al. 2021). Furthermore, phylogenetic analyses indicate that the shikimate pathways of many nutritional endosymbionts contain a glyphosate-sensitive enzyme. These findings highlight the importance of symbiont-mediated tyrosine supplementation for cuticle biosynthesis in insects, but also paint an alarming scenario regarding the use of glyphosate in light of recent declines in insect populations.
In leaf beetles (Chrysomelidae), we characterized the symbionts’ metabolism for Cassida rubiginosa (Bauer et al. 2020) and reconstructed the evolution of symbiont-mediated pectinase production and amino acid/vitamin provisioning across the reed beetle subfamily (Donaciinae), demonstrating life-stage specific benefits conferred by the symbionts and revealing both expansions and constraints of the host’s adaptive potential through symbiosis (Reis et al. 2020).
Another selective pressure herbivorous insects experience in nature are natural and human-made toxins. Glyphosate is a widely used herbicide that targets the shikimate pathway of plants and many microbes, but its impact on nutritional endosymbionts in insects remained poorly understood. In O. surinamensis, we found that glyphosate inhibits symbiont establishment during host development and abolishes the mutualistic benefit on cuticle synthesis in adults, which could be partially rescued by dietary tyrosine supplementation (Kiefer et al. 2021). Furthermore, phylogenetic analyses indicate that the shikimate pathways of many nutritional endosymbionts contain a glyphosate-sensitive enzyme. These findings highlight the importance of symbiont-mediated tyrosine supplementation for cuticle biosynthesis in insects, but also paint an alarming scenario regarding the use of glyphosate in light of recent declines in insect populations.
In leaf beetles (Chrysomelidae), we characterized the symbionts’ metabolism for Cassida rubiginosa (Bauer et al. 2020) and reconstructed the evolution of symbiont-mediated pectinase production and amino acid/vitamin provisioning across the reed beetle subfamily (Donaciinae), demonstrating life-stage specific benefits conferred by the symbionts and revealing both expansions and constraints of the host’s adaptive potential through symbiosis (Reis et al. 2020).
Publications originating from the ERC SYMBeetle:
Bauer, E., Kaltenpoth, M.* & Salem, H.* (2020) Minimal fermentative metabolism fuels extracellular symbiont in leaf beetles. The ISME Journal 14: 866-870.
Kaltenpoth, M. & Flórez, L.V. (2020) Versatile and dynamic symbioses between insects and Burkholderia bacteria. Annual Review of Entomology 65: 145-170.
Lemoine, M., Engl, T. & Kaltenpoth, M. (2020) Microbial symbionts expanding or constraining abiotic niche space in insects. Current Opinion in Insect Science 39:14-20.
Semiatizki, A., Weiss, B., Bagim, S., Rohkin-Shalom, S., Kaltenpoth, M., Chiel, E. (2020) Effects, interactions and localization of Rickettsia and Wolbachia in the house fly parasitoid, Spalangia endius. Microbial Ecology 80: 718–728.
Reis, F., Kirsch, R., Pauchet, Y., Bauer, E., Bilz, L.C. Fukomori, K., Fukatsu, T., Kölsch, G., Kaltenpoth, M. (2020) Bacterial symbionts support larval sap feeding and adult folivory in (semi-)aquatic reed beetles. Nature Communications 11: 2964.
By using comparative genomics of the symbionts across a subfamily of semi-aquatic leaf beetles, we could reveal for the first time that a single symbiont provides multiple benefits that are important in different life stages of the beetle host: While symbiont-encoded pectinases are likely important for the adults’ folivorous lifestyle, the sap-feeding larvae benefit from essential amino acid and vitamin provisioning by the symbionts. Furthermore, phylogenomic reconstructions reveal multiple independent losses of pectinase genes from the symbiont genomes after the hosts switched to feeding on pectin-poor Poales plants. This convincingly shows that microbial symbionts cannot only expand their host’s ecological niche space, but also constrain its future adaptive potential, in the case of reed beetles effectively confining them to a pectin-poor diet after losses of the pectinase genes from the symbiont genome. This changes the prevailing view of symbiosis providing novel ecological traits and opening up novel ecological niches for the host.
See also our press release about the paper: https://www.uni-mainz.de/presse/aktuell/11586_ENG_HTML.php
Kaltenpoth, M. (2020) An endosymbiont's journey through metamorphosis of its insect host. Proceedings of the National Academy of Sciences of the USA 117 (35): 20994-20996.
Brückner, A., Kaltenpoth, M., Heethoff, M. (2020) De novo biosynthesis of simple aromatic compounds by an arthropod (Archegozetes longisetosus). Proceedings of the Royal Society B-Biological Sciences 287: 20201429.
Kiefer, J.S.T. Batsukh, S., Bauer, E., Hirota, B., Weiss, B., Wierz, J., Fukatsu, T., Kaltenpoth, M., Engl, T. (2021) Inhibition of a nutritional endosymbiont by glyphosate abolishes mutualistic benefit on cuticle synthesis in Oryzaephilus surinamensis. Communications Biology 4:554.
This study raises awareness of the potential consequences of using an herbicide targeting the shikimate pathway for insects that harbor nutritional endosymbionts. As such, it provided important insights to the scientific community and the public. On the other hand, the realization that we can impair intracellular symbionts with glyphosate provides an exciting novel approach for manipulating symbionts encoding a shikimate pathway in a targeted manner. In future experiments, this provides a valuable tool for us to assess the importance of tyrosine-provisioning symbionts in other insects.
This study attracted a lot of attention in the scientific community but also the public, with press coverage in print media, radio, and TV, given the implications of our findings for the use of the widely used herbicide glyphosate on the well-being of insects with nutritional endosymbionts (see press release: https://www.ice.mpg.de/243630/PR_Kiefer-correct as well as MPG highlight: https://www.mpg.de/18086985/scientific-highlights-2021).
Wierz, J., Gaube, P., Klebsch, D., Kaltenpoth, M., Flórez, L. V. (2021) Transmission of bacterial symbionts with and without genome erosion between a beetle host and the plant environment. Frontiers in Microbiology 12: 715601.
Salem, H. and Kaltenpoth, M. (2022) Beetle-bacterial symbioses: Endless forms most functional. Annual Review of Entomology 67: 201-219.
Kanyile, S.N. Engl, T., Kaltenpoth, M. (2022) Nutritional symbionts enhance structural defence against predation and fungal infection in a grain pest beetle. Journal of Experimental Biology 225 (1): jeb243593.
By combining symbiont manipulation with predation and infection assays, we demonstrate that the acceleration of cuticle development after metamorphosis in symbiotic O. surinamensis allows them to escape the vulnerable phase of early adulthood more rapidly than their aposymbiotic counterparts. These results change our unilateral view on nutritional symbioses by showing that endosymbiont-providing nutrients can have far-reaching impacts beyond the direct nutritional benefits, including protection from biotic and abiotic stressors.
Bauer, E., Kaltenpoth, M.* & Salem, H.* (2020) Minimal fermentative metabolism fuels extracellular symbiont in leaf beetles. The ISME Journal 14: 866-870.
Kaltenpoth, M. & Flórez, L.V. (2020) Versatile and dynamic symbioses between insects and Burkholderia bacteria. Annual Review of Entomology 65: 145-170.
Lemoine, M., Engl, T. & Kaltenpoth, M. (2020) Microbial symbionts expanding or constraining abiotic niche space in insects. Current Opinion in Insect Science 39:14-20.
Semiatizki, A., Weiss, B., Bagim, S., Rohkin-Shalom, S., Kaltenpoth, M., Chiel, E. (2020) Effects, interactions and localization of Rickettsia and Wolbachia in the house fly parasitoid, Spalangia endius. Microbial Ecology 80: 718–728.
Reis, F., Kirsch, R., Pauchet, Y., Bauer, E., Bilz, L.C. Fukomori, K., Fukatsu, T., Kölsch, G., Kaltenpoth, M. (2020) Bacterial symbionts support larval sap feeding and adult folivory in (semi-)aquatic reed beetles. Nature Communications 11: 2964.
By using comparative genomics of the symbionts across a subfamily of semi-aquatic leaf beetles, we could reveal for the first time that a single symbiont provides multiple benefits that are important in different life stages of the beetle host: While symbiont-encoded pectinases are likely important for the adults’ folivorous lifestyle, the sap-feeding larvae benefit from essential amino acid and vitamin provisioning by the symbionts. Furthermore, phylogenomic reconstructions reveal multiple independent losses of pectinase genes from the symbiont genomes after the hosts switched to feeding on pectin-poor Poales plants. This convincingly shows that microbial symbionts cannot only expand their host’s ecological niche space, but also constrain its future adaptive potential, in the case of reed beetles effectively confining them to a pectin-poor diet after losses of the pectinase genes from the symbiont genome. This changes the prevailing view of symbiosis providing novel ecological traits and opening up novel ecological niches for the host.
See also our press release about the paper: https://www.uni-mainz.de/presse/aktuell/11586_ENG_HTML.php
Kaltenpoth, M. (2020) An endosymbiont's journey through metamorphosis of its insect host. Proceedings of the National Academy of Sciences of the USA 117 (35): 20994-20996.
Brückner, A., Kaltenpoth, M., Heethoff, M. (2020) De novo biosynthesis of simple aromatic compounds by an arthropod (Archegozetes longisetosus). Proceedings of the Royal Society B-Biological Sciences 287: 20201429.
Kiefer, J.S.T. Batsukh, S., Bauer, E., Hirota, B., Weiss, B., Wierz, J., Fukatsu, T., Kaltenpoth, M., Engl, T. (2021) Inhibition of a nutritional endosymbiont by glyphosate abolishes mutualistic benefit on cuticle synthesis in Oryzaephilus surinamensis. Communications Biology 4:554.
This study raises awareness of the potential consequences of using an herbicide targeting the shikimate pathway for insects that harbor nutritional endosymbionts. As such, it provided important insights to the scientific community and the public. On the other hand, the realization that we can impair intracellular symbionts with glyphosate provides an exciting novel approach for manipulating symbionts encoding a shikimate pathway in a targeted manner. In future experiments, this provides a valuable tool for us to assess the importance of tyrosine-provisioning symbionts in other insects.
This study attracted a lot of attention in the scientific community but also the public, with press coverage in print media, radio, and TV, given the implications of our findings for the use of the widely used herbicide glyphosate on the well-being of insects with nutritional endosymbionts (see press release: https://www.ice.mpg.de/243630/PR_Kiefer-correct as well as MPG highlight: https://www.mpg.de/18086985/scientific-highlights-2021).
Wierz, J., Gaube, P., Klebsch, D., Kaltenpoth, M., Flórez, L. V. (2021) Transmission of bacterial symbionts with and without genome erosion between a beetle host and the plant environment. Frontiers in Microbiology 12: 715601.
Salem, H. and Kaltenpoth, M. (2022) Beetle-bacterial symbioses: Endless forms most functional. Annual Review of Entomology 67: 201-219.
Kanyile, S.N. Engl, T., Kaltenpoth, M. (2022) Nutritional symbionts enhance structural defence against predation and fungal infection in a grain pest beetle. Journal of Experimental Biology 225 (1): jeb243593.
By combining symbiont manipulation with predation and infection assays, we demonstrate that the acceleration of cuticle development after metamorphosis in symbiotic O. surinamensis allows them to escape the vulnerable phase of early adulthood more rapidly than their aposymbiotic counterparts. These results change our unilateral view on nutritional symbioses by showing that endosymbiont-providing nutrients can have far-reaching impacts beyond the direct nutritional benefits, including protection from biotic and abiotic stressors.