Expression analysis of WRKY genes from Poncirus trifoliata in response to pathogen infection

The majority of WRKY transcription factors (TFs) play a role in the regulation of defense response in plants. Three WRKY genes, PtrWRKY1, PtrWRKY2 and PtrWRKY3, were previously identified in Poncirus and their expressions were characterized in response to cold and drought in Poncirus and Citrus. In this study, expressions of these WRKY genes were studied in response to infection with two major pathogens of Citrus, Citrus tristeza virus (CTV) and Phytophthora citrophthora, in resistant Poncirus and susceptible pummelo (Citrus grandis) plants. Northern blot analysis showed that the expression of the PtrWRKY1 gene was induced earlier and stronger in Poncirus than in pummelo in response to CTV infection. On the other hand, the expression of the PtrWRKY1 gene was not altered in response to P. citrophthora infection neither in Poncirus nor in pummelo. When the expression of the PtrWRKY2 gene was analyzed, it was repressed by CTV inoculation in Poncirus plants, whereas the expression was not changed in response ...