投稿日: 投稿者: atani カテゴリー: 気になる

J Integr Plant Biol. 2026 Apr 28. doi: 10.1111/jipb.70273. Online ahead of print.

ABSTRACT

Citrus bacterial canker (CBC) is a globally important citrus disease caused by Xanthomonas citri subsp. citri (Xcc). Increasing evidence shows that the plant microbiome is crucial for host growth performance and health maintenance, among which the keystone taxa stand out due to their indispensable roles in microbiome homeostasis. However, how keystone taxa in the phyllosphere microbiome contribute to disease resistance remains unclear. In this study, we characterized the phyllosphere bacterial community of pomelo across an annual cycle and found that amino acids in leaves were the main drivers of the bacterial community structure. Meanwhile, five OTUs were identified as keystone taxa. A total of 587 phyllosphere bacterial strains were isolated, among which six strains belonging to Methylobacterium, Sphingomonas, Massilia, and Paenibacillus were identified as the corresponding keystone strains. We further constructed a consortium with these six strains to test its role in controlling CBC in planta. Network analysis reveals that consortium inoculation increased the phyllosphere bacterial community stability, whereas Xcc inoculation decreased it. However, dual inoculation of the consortium and Xcc restored community stability compared to the control. Interestingly, the inoculated keystone strains, if not all, still appeared as keystone taxa in the microbiomes of the control, consortium inoculation, and dual inoculation treatments, but not in the Xcc-inoculated treatment. Moreover, the consortium inoculation significantly increased the defense-related enzyme activities such as PPO, POD, and PAL in leaves, suggesting a triggered plant immune response. In vitro assays indicated that these keystone strains showed either antagonistic activity against Xcc or siderophore-producing activity. Finally, the consortium inoculation significantly reduced the disease index by 78% in planta. Taken together, these results suggest that the keystone taxa of the phyllosphere microbiome can confer disease resistance to the host via multiple mechanisms, especially by maintaining phyllosphere microbiome homeostasis.

  • カンキツかいよう病（原因菌 Xanthomonas citri）に対する葉圏微生物の役割に着目
  • 特にキーストーンタクサ（群集維持に重要な微生物）の機能は未解明
  • ポメロ葉圏微生物を年間で解析 → アミノ酸が群集構造の主要因
  • 5つのOTUをキーストーンとして同定
  • 587株を分離 → Methylobacterium など6株をキーストーン菌として特定
  • これら6株でコンソーシアを構築
  • コンソーシア接種で葉圏微生物群集の安定性が向上
  • 病原菌単独接種では群集が不安定化
  • 両者同時接種で安定性が回復
  • コンソーシア接種により防御酵素（PPO, POD, PAL）が活性化
  • in vitroで拮抗作用やシデロフォア産生を確認
  • 植物体で病害指数を78%低減
  • キーストーン微生物は群集安定化と多面的機構により病害抵抗性を付与
  • キーストーン微生物を入れるだけで、葉圏の“バランス”が戻る
  • 群集安定化＋免疫誘導＋拮抗作用の複合効果で病害を抑制
  • Methylobacterium を含むコンソーシア設計の有効性を示す