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Koskimäki JJ, Pohjanen J, Kvist J, Fester T, Härtig C, Podolich O, Fluch S, Edesi J, Häggman H, Pirttilä AM. The meristem-associated endosymbiont Methylorubrum extorquens DSM13060 reprograms development and stress responses of pine seedlings. Tree Physiol 2022; 42:391-410. [PMID: 34328183 PMCID: PMC8842435 DOI: 10.1093/treephys/tpab102] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 07/19/2021] [Indexed: 06/13/2023]
Abstract
Microbes living in plant tissues-endophytes-are mainly studied in crop plants where they typically colonize the root apoplast. Trees-a large carbon source with a high capacity for photosynthesis-provide a variety of niches for endophytic colonization. We have earlier identified a new type of plant-endophyte interaction in buds of adult Scots pine, where Methylorubrum species live inside the meristematic cells. The endosymbiont Methylorubrum extorquens DSM13060 significantly increases needle and root growth of pine seedlings without producing plant hormones, but by aggregating around host nuclei. Here, we studied gene expression and metabolites of the pine host induced by M. extorquens DSM13060 infection. Malic acid was produced by pine to potentially boost M. extorquens colonization and interaction. Based on gene expression, the endosymbiont activated the auxin- and ethylene (ET)-associated hormonal pathways through induction of CUL1 and HYL1, and suppressed salicylic and abscisic acid signaling of pine. Infection by the endosymbiont had an effect on pine meristem and leaf development through activation of GLP1-7 and ALE2, and suppressed flowering, root hair and lateral root formation by downregulation of AGL8, plantacyanin, GASA7, COW1 and RALFL34. Despite of systemic infection of pine seedlings by the endosymbiont, the pine genes CUL1, ETR2, ERF3, HYL, GLP1-7 and CYP71 were highly expressed in the shoot apical meristem, rarely in needles and not in stem or root tissues. Low expression of MERI5, CLH2, EULS3 and high quantities of ononitol suggest that endosymbiont promotes viability and protects pine seedlings against abiotic stress. Our results indicate that the endosymbiont positively affects host development and stress tolerance through mechanisms previously unknown for endophytic bacteria, manipulation of plant hormone signaling pathways, downregulation of senescence and cell death-associated genes and induction of ononitol biosynthesis.
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Affiliation(s)
- Janne J Koskimäki
- Ecology and Genetics Research Unit, University of Oulu, Paavo Havaksentie J1, FI-90014 Oulu, Finland
| | - Johanna Pohjanen
- Ecology and Genetics Research Unit, University of Oulu, Paavo Havaksentie J1, FI-90014 Oulu, Finland
| | - Jouni Kvist
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Haartmaninkatu 8, FI-00014 Helsinki, Finland
| | - Thomas Fester
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research – UFZ, Permoserstr. 15, 04318 Leipzig, Germany
| | - Claus Härtig
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research – UFZ, Permoserstr. 15, 04318 Leipzig, Germany
| | - Olga Podolich
- Institute of Molecular Biology and Genetics of NASU, Acad. Zabolotnoho str., 150 03680 Kyiv, Ukraine
| | | | - Jaanika Edesi
- Ecology and Genetics Research Unit, University of Oulu, Paavo Havaksentie J1, FI-90014 Oulu, Finland
- Production Systems, Tree Breeding, Natural Resources Institute Finland LUKE, FI-57200 Savonlinna, Finland
| | - Hely Häggman
- Ecology and Genetics Research Unit, University of Oulu, Paavo Havaksentie J1, FI-90014 Oulu, Finland
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Koivusaari P, Pohjanen J, Wäli PR, Ahonen SHK, Saravesi K, Markkola AM, Haapala K, Suokas M, Koskimäki JJ, Tejesvi MV, Pirttilä AM. Different endophyte communities colonize buds of sprouts compared with mature trees of mountain birch recovered from moth herbivory. Tree Physiol 2018; 38:1437-1444. [PMID: 29481688 DOI: 10.1093/treephys/tpy012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 01/26/2018] [Indexed: 06/08/2023]
Abstract
Plant meristems were previously thought to be sterile. Today, meristem-associated shoot endophytes are mainly reported as contaminants from plant tissue cultures, the number of observed species being very low. However, the few strains characterized have the capacity for infecting host cells and affecting plant growth and development. Here we studied the communities of endophytic bacteria in the buds of mountain birch (Betula pubescens ssp. czerepanovii (N. I. Orlova) Hämet-Ahti) exposed to winter moth (Operophtera brumata L.) herbivory, to identify differences between sprouts and branches of mature birch trees. Mountain birch of the high subarctic is cyclically exposed to winter moth and produces sprouts to generate new trees as a survival mechanism. The majority (54%) of operational taxonomic units belonged to Xanthomonadaceae and Pseudomonales of Proteobacteria. Most of the observed species were classified as Xanthomonas (28%). Sprout buds had the highest diversity, containing approximately three times more species, and significantly more (43%) Pseudomonas species than the mature trees (14%). Our results demonstrate that endophytic communities of buds are richer than previously thought. We suggest that the meristem-associated endophytes should be studied further for a possible role in sprouting and aiding regeneration of trees.
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Affiliation(s)
| | | | - Piippa R Wäli
- Ecology and Genetics, University of Oulu, Oulu, Finland
| | | | | | | | - Kaisa Haapala
- Ecology and Genetics, University of Oulu, Oulu, Finland
| | - Marko Suokas
- Ecology and Genetics, University of Oulu, Oulu, Finland
| | | | - Mysore V Tejesvi
- Ecology and Genetics, University of Oulu, Oulu, Finland
- Chain Antimicrobials, Teknologiantie 2, Oulu, Finland
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Pohjanen J, Koskimäki JJ, Sutela S, Ardanov P, Suorsa M, Niemi K, Sarjala T, Häggman H, Pirttilä AM. Interaction with ectomycorrhizal fungi and endophytic Methylobacterium affects nutrient uptake and growth of pine seedlings in vitro. Tree Physiol 2014; 34:993-1005. [PMID: 25149086 DOI: 10.1093/treephys/tpu062] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Tissues of Scots pine (Pinus sylvestris L.) contain several endophytic microorganisms of which Methylobacterium extorquens DSM13060 is a dominant species throughout the year. Similar to other endophytic bacteria, M. extorquens is able to colonize host plant tissues without causing any symptoms of disease. In addition to endophytic bacteria, plants associate simultaneously with a diverse set of microorganisms. Furthermore, plant-colonizing microorganisms interact with each other in a species- or strain-specific manner. Several studies on beneficial microorganisms interacting with plants have been carried out, but few deal with interactions between different symbiotic organisms and specifically, how these interactions affect the growth and development of the host plant. Our aim was to study how the pine endophyte M. extorquens DSM13060 affects pine seedlings and how the co-inoculation with ectomycorrhizal (ECM) fungi [Suillus variegatus (SV) or Pisolithus tinctorius (PT)] alters the response of Scots pine. We determined the growth, polyamine and nutrient contents of inoculated and non-inoculated Scots pine seedlings in vitro. Our results show that M. extorquens is able to improve the growth of seedlings at the same level as the ECM fungi SV and PT do. The effect of co-inoculation using different symbiotic organisms was seen in terms of changes in growth and nutrient uptake. Inoculation using M. extorquens together with ECM fungi improved the growth of the host plant even more than single ECM inoculation. Symbiotic organisms also had a strong effect on the potassium content of the seedling. The results indicate that interaction between endophyte and ECM fungus is species dependent, leading to increased or decreased nutrient content and growth of pine seedlings.
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Affiliation(s)
- Johanna Pohjanen
- Department of Biology, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland
| | - Janne J Koskimäki
- Department of Biology, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland
| | - Suvi Sutela
- Department of Biology, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland
| | - Pavlo Ardanov
- Department of Biology, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland
| | - Marja Suorsa
- Department of Biology, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland
| | - Karoliina Niemi
- Finnish Forest Industries Federation, PO Box 336, FIN-00171 Helsinki, Finland
| | - Tytti Sarjala
- Finnish Forest Research Institute, Parkano Research Unit, FIN-39700 Parkano, Finland
| | - Hely Häggman
- Department of Biology, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland
| | - Anna Maria Pirttilä
- Department of Biology, University of Oulu, PO Box 3000, FIN-90014 Oulu, Finland
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Nasopoulou C, Pohjanen J, Koskimäki JJ, Zabetakis I, Pirttilä AM. Localization of strawberry (Fragaria x ananassa) and Methylobacterium extorquens genes of strawberry flavor biosynthesis in strawberry tissue by in situ hybridization. J Plant Physiol 2014; 171:1099-1105. [PMID: 24973582 DOI: 10.1016/j.jplph.2014.03.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Revised: 03/20/2014] [Accepted: 03/23/2014] [Indexed: 06/03/2023]
Abstract
Strawberry flavor is one of the most popular fruit flavors worldwide, with numerous applications in the food industry. In addition, the biosynthetic origin of the most important strawberry flavor components, such as 2,5-dimethyl-4-hydroxy-2H-furan-3-one (DMHF), is a challenging research area. DMHF's precursor, 2-hydroxy-propanal (or lactaldehyde), is biosynthesized by the endophytic bacterium Methylobacterium extorquens (M. extorquens). In particular, the alcohol dehydrogenase (ADH) enzymes of M. extorquens are involved in the biogenesis of DMHF precursors since they have the capacity to oxidize the strawberry-derived 1,2-propanediol to lactaldehyde. In this study, the expression of the endophytic ADH and the plant DMHF biosynthesis genes was examined in the tissues of raw and ripe strawberry receptacles by in situ hybridization. The presence of endophytic bacteria was studied in the same tissues by probes targeting bacterial 16S ribosomal ribonucleic acid. Hybridization signals of probes specific for endophytic ADH and plant DMHF biosynthesis genes, as well as bacteria-specific probes, were detected in the same locations. The probes were localized near the plasma membranes or intercellular spaces of cortical and vascular tissues of the receptacle, and intracellularly in the tissues of achenes. By localizing the expression of the endophytic methanol ADH and plant DMHF biosynthesis genes to the same tissues, we have reinforced our original hypothesis that an intimate symbiotic relationship between strawberry and endophytic cells exists and leads to the biosynthesis of DMHF.
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Affiliation(s)
- Constantina Nasopoulou
- Department of Biology, University of Oulu, PO Box 3000, 90014, Oulu, Finland; Department of Chemistry, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, 157 84, Athens, Greece.
| | - Johanna Pohjanen
- Department of Biology, University of Oulu, PO Box 3000, 90014, Oulu, Finland
| | - Janne J Koskimäki
- Department of Biology, University of Oulu, PO Box 3000, 90014, Oulu, Finland
| | - Ioannis Zabetakis
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, 157 84, Athens, Greece
| | - Anna Maria Pirttilä
- Department of Biology, University of Oulu, PO Box 3000, 90014, Oulu, Finland
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