Comparative ultrastructure of nonwounded Mexican lime and yuzu leaves infected with the citrus canker bacterium Xanthomonas citri pv. citri

Jung Lee In, Woo Kim Ki, Wook Hyun Jae, Hoon Lee Yong, Woo Park Eun

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Ultrastructural aspects of citrus canker development were investigated in nonwounded leaves of citrus species by transmission electron microscopy (TEM). A susceptible species Mexican lime and a resistant species Yuzu were spray-inoculated with a virulent strain of Xanthomonas citri pv. citri. Initial symptoms occurred on Mexican lime ̃9 days after inoculation, whereas they appeared on Yuzu mostly 11 days after inoculation. In Mexican lime leaves, the bacterial invasion was usually accompanied by host cell wall dissolution and cellular disruption. Fibrillar materials from degenerated cell walls were usually found in intercellular spaces. Damaged host cells with necrotic cytoplasm showed the localized separation of plasma membrane from the cell wall. Bacterial multiplication and electron-transparent capsule-like structures around bacteria were commonly observed. Meanwhile, cell wall protuberances were prominent outside host cell walls in response to bacterial invasion in Yuzu leaves. Occlusion of intercellular spaces was also formed by the fusion of two or more individual cell wall protuberances originated from two adjacent host cells. Papillae-like materials accumulated locally within host cells in close proximity to bacteria. Some bacteria were found to be undergoing degeneration in xylem vessels. Also, the shrunken, inactive bacteria were surrounded by electron-translucent fibrillar materials in intercellular spaces, implying bacterial immobilization. These cellular responses are thought to be the consequences of defense responses of Yuzu leaves to invading bacteria. In both citrus species, X. citri pv. citri contained polyphosphate bodies showing electron-dense and elliptical structures in cytoplasm.

Original languageEnglish
Pages (from-to)507-516
Number of pages10
JournalMicroscopy Research and Technique
Volume72
Issue number7
DOIs
StatePublished - Jul 2009

Keywords

  • Asiatic citrus canker
  • Biofilm
  • Extracellular polysaccharides
  • Polyphosphate bodies
  • Xanthomonas citri pv. citri

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