How Xanthomonas manipulates the plant
U. BONAS (1) (1) University of Halle, Germany

Pathogenicity of most Gram-negative plant-pathogenic bacteria depends on the type III secretion (T3S) system which translocates effector proteins (T3Es) into the plant cell cytosol. In susceptible plants, T3Es interfere with host cell processes to the benefit of the pathogen and allow its proliferation. In resistant plants, plant resistance genes mediate recognition of an individual T3E often resulting in a hypersensitive response (HR), a rapid and localized programmed cell death restricting pathogen multiplication. We study the interaction between the bacterial spot pathogen Xanthomonas campestris pv. vesicatoria (Xcv) and its host plants pepper and tomato. The bacteria enter the plant tissue via stomata or wounds and settle down in the intercellular spaces which induces expression of the T3S system, a complex nanomachine spanning both bacterial membranes. The Xcv T3S system injects more than 30 different T3Es into the plant cell, termed Avr (avirulence protein), if they were identified many years ago, or Xop (Xanthomonas outer protein). As most single T3Es gene deletion mutants of Xcv behave like the wild type they likely have redundant activities in the plant cell. Major aims of our current research are to understand the role of small, non-coding RNAs in Xcv virulence and to identify the plant targets of Xops. Among the T3Es from Xcv are plant immunity suppressors, cell death inducers, a ubiquitin ligase, a transcription factor and proteins of unknown function. Selected T3Es will be discussed.

Abstract Number: P2-1
Session Type: Plenary