Neumann C.,Justus Liebig University |
Fraiture M.,University of Tübingen |
Hernandez-Reyes C.,Justus Liebig University |
Akum F.N.,Justus Liebig University |
And 10 more authors.
Frontiers in Microbiology | Year: 2014
Salmonella is one of the most prominent causes of food poisoning and growing evidence indicates that contaminated fruits and vegetables are an increasing concern for human health. Successful infection demands the suppression of the host immune system, which is often achieved via injection of bacterial effector proteins into host cells. In this report we present the function of Salmonella effector protein in plant cell, supporting the new concept of trans-kingdom competence of this bacterium. We screened a range of Salmonella Typhimurium effector proteins for interference with plant immunity. Among these, the phosphothreonine lyase SpvC attenuated the induction of immunity-related genes when present in plant cells. Using in vitro and in vivo systems we show that this effector protein interacts with and dephosphorylates activated Arabidopsis Mitogen-activated Protein Kinase 6 (MPK6), thereby inhibiting defense signaling. Moreover, the requirement of Salmonella SpvC was shown by the decreased proliferation of the δspvC mutant in Arabidopsis plants. These results suggest that some Salmonella effector proteins could have a conserved function during proliferation in different hosts. The fact that Salmonella and other Enterobacteriaceae use plants as hosts strongly suggests that plants represent a much larger reservoir for animal pathogens than so far estimated. © 2014 Neumann, Fraiture, Hernàndez-reyes, Akum, Virlogeuxpayant, Chen, Pateyron, Colcombet, Kogel, Hirt, Brunner and Schikora.
Smeets K.,Hasselt University |
Opdenakker K.,Hasselt University |
Remans T.,Hasselt University |
Forzani C.,URGV Plant Genomics |
And 3 more authors.
Plant, Cell and Environment | Year: 2013
The hypothesis that mitogen-activated protein kinase (MAPK) signalling is important in plant defences against metal stress has become accepted in recent years. To test the role of oxidative signal-inducible kinase (OXI1) in metal-induced oxidative signalling, the responses of oxi1 knockout lines to environmentally realistic cadmium (Cd) and copper (Cu) concentrations were compared with those of wild-type plants. A relationship between OXI1 and the activation of lipoxygenases and other initiators of oxylipin production was observed under these stress conditions, suggesting that lipoxygenase-1 may be a downstream component of OXI1 signalling. Metal-specific differences in OXI1 action were observed. For example, OXI1 was required for the up-regulation of antioxidative defences such as catalase in leaves and Fe-superoxide dismutase in roots, following exposure to Cu, processes that may involve the MEKK1-MKK2-WRKY25 cascade. Moreover, the induction of Cu/Zn superoxide dismutases in Cu-exposed leaves was regulated by OXI1 in a manner that involves fluctuations in the expression of miRNA398. These observations contrast markedly with the responses to Cd exposure, which also involves OXI1-independent pathways but rather involves changes in components mediating intracellular communication. Knowledge on the mechanism of action is necessary when different stress factors are compared. Via knock-out experiments, the importance of OXI1 action appeared metal-specific. OXI1 is required for the cellular defence activation during copper stress, which contrasts markedly with the responses to cadmium exposure. These also involve OXI1-independent pathways and components mediating intracellular communication. © 2012 Blackwell Publishing Ltd.