Bacterial hrp and Avirulence Genes are Key Determinants in Plant-Pathogen Interactions

  • Ulla Bonas
  • Guido Van den Ackerveken


Among the 1600 different species known in the bacterial kingdom only a small number are plant pathogenic. In fact, most pathogens can only infect a limited number of host plant species. On the other hand, many bacteria live in the plant’s phyllosphere and rhizosphere without causing any harm. To be successful as a pathogen, i.e., live on the expense of the host and cause damage that may even kill the host, the bacterium has to overcome the plant’s physical barriers and defence responses. During evolution plant pathogenic bacteria have acquired multiple functions that enable them to colonise and multiply in living plant tissue. Due to this specialisation the host range is often limited to a few plant species. In the well studied plant pathogens Agrobacterium tumefaciens, A. rhizogenes, and A. vitis virulence genes are located on an endogenous plasmid and are responsible for the transfer of the so-called T-DNA region from the same plasmid to the plant nucleus. The integrated T-DNA contains genes for plant hormone metabolism and for the synthesis of opines which are expressed in the plant cell. Consequently, the transformed plant tissue develops into tumours or hairy roots; the opines are utilised by the surrounding bacteria. For excellent more comprehensive reviews on Agrobacterium see Zambryski (1992) and Winans (1992). This chapter will focus on subspecies of the gram-negative genera Erwinia, Pseudomonas, and Xanthomonas which cause numerous diseases in important crop plants. These bacteria have evolved tools different from Agrobacterium in order to infect the host plant.


Xanthomonas Campestris Yersinia Pestis Avirulence Gene Plant Pathogenic Bacterium Nonhost Plant 
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Copyright information

© Plenum Press, New York 1996

Authors and Affiliations

  • Ulla Bonas
    • 1
  • Guido Van den Ackerveken
    • 1
  1. 1.Institut des Sciences VégétalesCNRSGif-sur-YvetteFrance

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