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Rico-Jiménez M, Udaondo Z, Krell T, Matilla MA. Auxin-mediated regulation of susceptibility to toxic metabolites, c-di-GMP levels, and phage infection in the rhizobacterium Serratia plymuthica. mSystems 2024; 9:e0016524. [PMID: 38837409 DOI: 10.1128/msystems.00165-24] [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: 02/02/2024] [Accepted: 04/26/2024] [Indexed: 06/07/2024] Open
Abstract
The communication between plants and their microbiota is highly dynamic and involves a complex network of signal molecules. Among them, the auxin indole-3-acetic acid (IAA) is a critical phytohormone that not only regulates plant growth and development, but is emerging as an important inter- and intra-kingdom signal that modulates many bacterial processes that are important during interaction with their plant hosts. However, the corresponding signaling cascades remain largely unknown. Here, we advance our understanding of the largely unknown mechanisms by which IAA carries out its regulatory functions in plant-associated bacteria. We showed that IAA caused important changes in the global transcriptome of the rhizobacterium Serratia plymuthica and multidisciplinary approaches revealed that IAA sensing interferes with the signaling mediated by other pivotal plant-derived signals such as amino acids and 4-hydroxybenzoic acid. Exposure to IAA caused large alterations in the transcript levels of genes involved in amino acid metabolism, resulting in significant metabolic alterations. IAA treatment also increased resistance to toxic aromatic compounds through the induction of the AaeXAB pump, which also confers resistance to IAA. Furthermore, IAA promoted motility and severely inhibited biofilm formation; phenotypes that were associated with decreased c-di-GMP levels and capsule production. IAA increased capsule gene expression and enhanced bacterial sensitivity to a capsule-dependent phage. Additionally, IAA induced the expression of several genes involved in antibiotic resistance and led to changes in the susceptibility and responses to antibiotics with different mechanisms of action. Collectively, our study illustrates the complexity of IAA-mediated signaling in plant-associated bacteria. IMPORTANCE Signal sensing plays an important role in bacterial adaptation to ecological niches and hosts. This communication appears to be particularly important in plant-associated bacteria since they possess a large number of signal transduction systems that respond to a wide diversity of chemical, physical, and biological stimuli. IAA is emerging as a key inter- and intra-kingdom signal molecule that regulates a variety of bacterial processes. However, despite the extensive knowledge of the IAA-mediated regulatory mechanisms in plants, IAA signaling in bacteria remains largely unknown. Here, we provide insight into the diversity of mechanisms by which IAA regulates primary and secondary metabolism, biofilm formation, motility, antibiotic susceptibility, and phage sensitivity in a biocontrol rhizobacterium. This work has important implications for our understanding of bacterial ecology in plant environments and for the biotechnological and clinical applications of IAA, as well as related molecules.
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Affiliation(s)
- Miriam Rico-Jiménez
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Zulema Udaondo
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
- Department of Biomedical Informatics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, Spain
| | - Tino Krell
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Miguel A Matilla
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
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Chamard J, Faticov M, Blanchet FG, Chagnon PL, Laforest-Lapointe I. Interplay of biotic and abiotic factors shapes tree seedling growth and root-associated microbial communities. Commun Biol 2024; 7:360. [PMID: 38519711 PMCID: PMC10960049 DOI: 10.1038/s42003-024-06042-7] [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: 11/06/2023] [Accepted: 03/12/2024] [Indexed: 03/25/2024] Open
Abstract
Root-associated microbes can alleviate plant abiotic stresses, thus potentially supporting adaptation to a changing climate or to novel environments during range expansion. While climate change is extending plant species fundamental niches northward, the distribution and colonization of mutualists (e.g., arbuscular mycorrhizal fungi) and pathogens may constrain plant growth and regeneration. Yet, the degree to which biotic and abiotic factors impact plant performance and associated microbial communities at the edge of their distribution remains unclear. Here, we use root microscopy, coupled with amplicon sequencing, to study bacterial, fungal, and mycorrhizal root-associated microbial communities from sugar maple seedlings distributed across two temperate-to-boreal elevational gradients in southern Québec, Canada. Our findings demonstrate that soil pH, soil Ca, and distance to sugar maple trees are key drivers of root-associated microbial communities, overshadowing the influence of elevation. Interestingly, changes in root fungal community composition mediate an indirect effect of soil pH on seedling growth, a pattern consistent at both sites. Overall, our findings highlight a complex role of biotic and abiotic factors in shaping tree-microbe interactions, which are in turn correlated with seedling growth. These findings have important ramifications for tree range expansion in response to shifting climatic niches.
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Affiliation(s)
- Joey Chamard
- Département de biologie, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre Sève, Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre d'Étude de la Forêt, Université du Québec à Montréal, Montréal, QC, Canada
| | - Maria Faticov
- Département de biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
- Centre Sève, Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
- Centre d'Étude de la Forêt, Université du Québec à Montréal, Montréal, QC, Canada.
| | - F Guillaume Blanchet
- Département de biologie, Université de Sherbrooke, Sherbrooke, QC, Canada
- Département de mathématiques, Université de Sherbrooke, Sherbrooke, QC, Canada
- Département des sciences de la santé communautaire, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Pierre-Luc Chagnon
- Agriculture and Agri-food Canada, Saint-Jean-sur-Richelieu, QC, Canada
- Département des Sciences Biologiques, Université de Montréal, Montréal, QC, Canada
| | - Isabelle Laforest-Lapointe
- Département de biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
- Centre Sève, Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
- Centre d'Étude de la Forêt, Université du Québec à Montréal, Montréal, QC, Canada.
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Bass E. Getting to the root of divergent outcomes in the modulation of plant-soil feedbacks by benzoxazinoids. THE NEW PHYTOLOGIST 2024; 241:2316-2319. [PMID: 38263679 DOI: 10.1111/nph.19545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 01/08/2024] [Indexed: 01/25/2024]
Abstract
This article is a Commentary on Gfeller et al. (2024), 241: 2575–2588.
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Affiliation(s)
- Ethan Bass
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, 14853, USA
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Cecala JM, Vannette RL. Nontarget impacts of neonicotinoids on nectar-inhabiting microbes. Environ Microbiol 2024; 26:e16603. [PMID: 38494634 DOI: 10.1111/1462-2920.16603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 02/23/2024] [Indexed: 03/19/2024]
Abstract
Plant-systemic neonicotinoid (NN) insecticides can exert non-target impacts on organisms like beneficial insects and soil microbes. NNs can affect plant microbiomes, but we know little about their effects on microbial communities that mediate plant-insect interactions, including nectar-inhabiting microbes (NIMs). Here we employed two approaches to assess the impacts of NN exposure on several NIM taxa. First, we assayed the in vitro effects of six NN compounds on NIM growth using plate assays. Second, we inoculated a standardised NIM community into the nectar of NN-treated canola (Brassica napus) and assessed microbial survival and growth after 24 h. With few exceptions, in vitro NN exposure tended to decrease bacterial growth metrics. However, the magnitude of the decrease and the NN concentrations at which effects were observed varied substantially across bacteria. Yeasts showed no consistent in vitro response to NNs. In nectar, we saw no effects of NN treatment on NIM community metrics. Rather, NIM abundance and diversity responded to inherent plant qualities like nectar volume. In conclusion, we found no evidence that NIMs respond to field-relevant NN levels in nectar within 24 h, but our study suggests that context, specifically assay methods, time and plant traits, is important in assaying the effects of NNs on microbial communities.
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Affiliation(s)
- Jacob M Cecala
- Department of Entomology & Nematology, University of California, Davis, California, USA
| | - Rachel L Vannette
- Department of Entomology & Nematology, University of California, Davis, California, USA
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Aoki N, Shimasaki T, Yazaki W, Sato T, Nakayasu M, Ando A, Kishino S, Ogawa J, Masuda S, Shibata A, Shirasu K, Yazaki K, Sugiyama A. An isoflavone catabolism gene cluster underlying interkingdom interactions in the soybean rhizosphere. ISME COMMUNICATIONS 2024; 4:ycae052. [PMID: 38707841 PMCID: PMC11069340 DOI: 10.1093/ismeco/ycae052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 02/19/2024] [Accepted: 04/03/2024] [Indexed: 05/07/2024]
Abstract
Plant roots secrete various metabolites, including plant specialized metabolites, into the rhizosphere, and shape the rhizosphere microbiome, which is crucial for the plant health and growth. Isoflavones are major plant specialized metabolites found in legume plants, and are involved in interactions with soil microorganisms as initiation signals in rhizobial symbiosis and as modulators of the legume root microbiota. However, it remains largely unknown the molecular basis underlying the isoflavone-mediated interkingdom interactions in the legume rhizosphere. Here, we isolated Variovorax sp. strain V35, a member of the Comamonadaceae that harbors isoflavone-degrading activity, from soybean roots and discovered a gene cluster responsible for isoflavone degradation named ifc. The characterization of ifc mutants and heterologously expressed Ifc enzymes revealed that isoflavones undergo oxidative catabolism, which is different from the reductive metabolic pathways observed in gut microbiota. We further demonstrated that the ifc genes are frequently found in bacterial strains isolated from legume plants, including mutualistic rhizobia, and contribute to the detoxification of the antibacterial activity of isoflavones. Taken together, our findings reveal an isoflavone catabolism gene cluster in the soybean root microbiota, providing molecular insights into isoflavone-mediated legume-microbiota interactions.
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Affiliation(s)
- Noritaka Aoki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Tomohisa Shimasaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
- Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Wataru Yazaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Tomoaki Sato
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Masaru Nakayasu
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Akinori Ando
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Shigenobu Kishino
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Jun Ogawa
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Sachiko Masuda
- Plant Immunity Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa 230-0045, Japan
| | - Arisa Shibata
- Plant Immunity Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa 230-0045, Japan
| | - Ken Shirasu
- Plant Immunity Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa 230-0045, Japan
| | - Kazufumi Yazaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Akifumi Sugiyama
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
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