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Visualization of root extracellular traps in an ectomycorrhizal woody plant (Pinus densiflora) and their interactions with root-associated bacteria


  • Shirakawa, Makoto Graduate School of Agricultural and Life Sciences, The University of Tokyo https://orcid.org/0000-0003-3454-6768
  • Norihisa Matsushita Graduate School of Agricultural and Life Sciences, The University of Tokyo
  • Kenji Fukuda Graduate School of Agricultural and Life Sciences, The University of Tokyo




Border cells、 Japanese red pine、 Paraburkholderia、 Primary root、 Rhizobacteria、 Root mucilage


Ectomycorrhizal (ECM) woody plants, such as members of Pinaceae and Fagaceae, can acquire resistance to biotic and abiotic stresses through the formation of mycorrhiza with ECM fungi. However, germinated tree seedlings do not have mycorrhizae and it takes several weeks for ectomycorrhizae to form on their root tips. Therefore, to confer protection during the early growth stage, bare primary roots require defense mechanisms other than mycorrhization. Here, we attempted to visualize root extracellular traps (RETs), an innate root defense mechanism, in the primary root of Pinus densiflora and investigate the interactions with root-associated bacteria isolated from ECM and fine non-mycorrhizal roots. Histological and histochemical imaging and colony forming unit assays demonstrated that RETs in P. densiflora, mainly consisting of root-associated, cap-derived cells (AC-DCs) and large amounts of root mucilage, promoted bacterial colonization in the rhizosphere, despite also having bactericidal activity via extracellular DNA. Four rhizobacterial strains induced the production of reactive oxygen species (ROS) from host tree AC-DCs without being excluded from the rhizosphere of P. densiflora. In particular, applying two Paraburkholderia strains, PM O-EM8 and PF T-NM22, showed significant differences in the ROS levels from the control group. These results reveal an indirect contribution of rhizobacteria to host root defense, and suggest that root-associated bacteria could be a component of RETs as a first line of defense against root pathogens in the early growth stage of ECM woody plants.


The authors have no conflicts of interest associated with the article.

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投稿日時: 2023-03-15 11:49:56 UTC

公開日時: 2023-03-17 00:48:50 UTC