Javier Carrera, Santiago Elena, César Llave, Guillermo Rodrigo, Virgina Ruiz-Ferrer, Francisco Toro, Olivier Voinnet

Paper #: 11-10-049

Understanding the mechanisms by which plants trigger host defenses in response to viruses has been a challenging problem owing to the multiplicity of factors and complexity of interactions involved. The advent of genomic techniques, however, has opened the possibility to grasp a global picture of the interaction. Here, we used Arabidopsis thaliana to identify and compare genes that are differentially regulated upon infection with seven distinct (+)ssRNA and one ssDNA plant viruses. In a first approach, we established lists of genes differentially affected by each virus and compared their involvement in biological functions and metabolic processes. We found that phylogenetically-related viruses significantly alter the expression of similar genes and that viruses naturally infecting Brassicaceae display a greater overlap in the plant response. In a second approach, virus-regulated genes were contextualized using transcriptional and protein-protein interaction networks of A. thaliana. Our results confirm that host cells undergo significant reprogramming of their transcriptome during infection, which is possibly a central requirement for the mounting of host defenses. We uncovered a general mode of action in which perturbations preferentially affect genes that are highly connected, central and organized in modules. This indicates redundancy in the information transmission from virus effectors to immune response genes and allowed us to suggest that this over-triggering of hub proteins is a mechanism to confer robustness for expression of host defenses.