Nurcan Kocal

Suche


B4 Re-programming of plant metabolism by type III effectors from Xanthomonas campretris

Principal investigator
Sophia Sonnewald

Mentor
Andreas Burkovski

PhD exam: 21.07.2011

Nutrient acquisition of the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria

Xanthomonas campestris pv. vesicatoria (Xcv) is the causal agent of bacterial spot disease in tomato and pepper plants. The pathogenicity of Xcv depends on a type III protein secretion system (TTSS) delivering effector proteins supposed to be involved in suppression of plant defence and nutrient acquisition. We exploit the compatible interaction between Xcv and tomato plants to investigate the role of cell wall-bound invertase (cw-Inv) using transgenic tomato plants silenced for the major leaf cw-Inv isoforms. Cw-Inv cleaves sucrose into glucose and fructose providing nutrients for bacterial growth and sugar signals for induction of plant defence responses and down-regulation of photosynthesis. Xcv infection of transgenic tomato plants caused delayed symptom development and inhibition of photosynthesis as compared to wild-type. Moreover, induction of senescence-associated and PR genes was delayed. Interestingly, bacterial growth in planta was not altered in cw-Inv-silenced tomato plants, suggesting that hexoses are not the major carbon source of Xcv. To further investigate the nutrition strategy of Xcv, we generated knockout mutants in a putative sucrose symporter (SymI) and a citrate transporter (CitH). We could show that Xcv ΔsymI and ΔcitH strains did not grow in medium containing sucrose or citrate as the sole carbon source, respectively. Both strains caused delayed symptom developmentwhen infected in planta. This effect was more pronounced for the ΔcitH mutant which correlated with a reduced bacterial growth suggesting that citrate is an important carbon source for Xcv. Growth of Xcv ΔsymI was unchanged in planta indicating that delayed symptom development might be attributed to the absence of sugar signals. For this purpose expression of selected marker genes is being analysed. Furthermore, Xcv strains defective in other sugar- and malate- transporter will be generated to get detailed insights into its nutrient acquisition strategies.

Figure: Development of disease symptoms upon treatment with Xcv in Lin8 RNAi plants. Source leaves were infiltrated with Xcv 75-3 or a T3SS-deficient (Δ hrpX) strain at a concentration of 5*104 cfu*ml-1. As control leaves were inoculated with 10 mM MgCl2. Infected leaves were photographed 16 days after infection. (A) MM wild type. (B) Lin8-RNAi # 33. (C) Lin8-RNAi # 50. (D) Lin8-RNAi # 57.

 

Publications

Kocal, N., Sonnewald, U. and Sonnewald, S. (2008). Cell wall-bound invertase limits sucrose export and is involved in symptom development and inhibition of photosynthesis during compatible interaction between tomato and Xanthomonas campestris pv vesicatoria. Plant Physiol 148, 1523-1536.

 

Presentations

September 2009 First Annual Retreat, Erlangen School of Molecular Communication, Schloss Atzelsberg, Atzelsberg, Germany
Nutrient acquisition of the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria
Talk
     
September 2009 Botanikertagung: Plants for the future, Leipzig, Germany
Nutrient acquisition of the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria
Talk
     
April 2008 25.Wallenfelser Rundgespräch zur Pflanzenbiochemie, Wallenfels, Germany
„Die Rolle der Zellwandinvertase bei der Regulation der Photosynthese und der Pflanzenabwehr“
Talk
     
February 2008 21.Tagung der Molekularbiologie der Pflanzen, Dabringhausen, Germany
„RNAi vermittelte Suppression der Zellwand-Invertase beeinflusst die Photosynthese in Tomatenblättern nach Infektion mit Xanthomonas campestris pv. vesicatoria.“
Poster