European Journal of Plant Pathology

, Volume 130, Issue 2, pp 143–154 | Cite as

A single amino acid substitution in PthA of Xanthomonas axonopodis pv. citri altering canker formation on grapefruit leaves

  • Hsin-Cheng LinEmail author
  • Mu-Kuei Chu
  • Yuang-Chuen Lin
  • Wen-Ling Deng
  • Hsiang Chang
  • Shih-Tien Hsu
  • Kuo-Ching TzengEmail author


The typical citrus canker lesions produced by Xanthomonas axonopodis pv. citri are erumpent, callus-like, with water-soaked margins. Three novel atypical symptom-producing variants of X. axonopodis pv. citri were described recently in Taiwan. Only the variant designated as Af type produces typical erumpent canker lesions on Mexican lime (Citrus aurantifolia) but induces flat necrotic with water-soaked margin lesions on grapefruit leaves (C. paradisi). Two homologous pthA were cloned and characterized from strains XW19 (a typical canker lesion producing strain) and XW47 (a strain of Af type). The pthA homolog from XW19 was transformed into XW47. The transformant of XW47 induced typical erumpent canker lesions on grapefruit leaves. Sequence analyses of transformants XW19 and XW47 revealed over 99% homology in nucleotide and deduced amino acid sequences compared with pthA homologs deposited in GenBank. The amino acid residues located at positions 49, 286, 742 and 767 of PthA were different between XW47 and XW19. The PthA mutants with a single amino acid substitution at each of these four positions were constructed by site-directed mutagenesis. Modified PthA (S286P) from XW47 in transformant 47SP induced erumpent canker lesions on grapefruit leaves, whereas another modified PthA (P286S) from XW19 in transformant 47PS only induced flat necrotic lesions. These results suggested that a single amino acid substitution from either serine to proline or proline to serine at position 286 of PthA can alter canker formation by X. axonopodis pv. citri on grapefruit leaves.


Citrus Citrus bacterial canker pthA Site-directed mutagenesis Proline 



We thank Professor C.-J. Chang (Department of plant pathology, University of Georgia) for critically reviewing this manuscript and many valuable suggestions. This research was supported in part of grant from National Science Council (NSC 94-2313-B-005-068), Taiwan.


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Copyright information

© KNPV 2011

Authors and Affiliations

  • Hsin-Cheng Lin
    • 1
    Email author
  • Mu-Kuei Chu
    • 2
  • Yuang-Chuen Lin
    • 3
  • Wen-Ling Deng
    • 4
  • Hsiang Chang
    • 5
  • Shih-Tien Hsu
    • 4
  • Kuo-Ching Tzeng
    • 4
    Email author
  1. 1.Department of BiotechnologyChung Chou Institute of TechnologyChanghuaTaiwan
  2. 2.Department of Biological Science and TechnologyChung Hwa University of Medical TechnologyTainan CountyTaiwan
  3. 3.Graduate Institute of BiotechnologyNational Chung Hsing UniversityTaichungTaiwan
  4. 4.Department of Plant PathologyNational Chung-Hsing UniversityTaichungTaiwan
  5. 5.Department of BiotechnologyAsia UniversityTaichung CountyTaiwan

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