Molecular mechanisms involved in induced resistance signaling in Arabidopsis

Evolution has provided plants with sophisticated defensive strategies to "perceive" attack by pathogens and insects, and to translate that "perception" into an appropriate adaptive response. Plant innate immunity is based on a surprisingly complex response that is highly flexible in its capacity to recognize and respond to the invader encountered. In the past years, we explored Arabidopsis as a model to study the molecular basis of rhizobacteria-induced systemic resistance (ISR). We discovered novel components of the ISR signaling pathway and revealed that priming for augmented expression of pathogenresponsive genes plays an important role in this type of induced resistance. Currently our research is also focused on the question: how are plants capable of integrating microbial- and insect-induced signals into defense responses that are specifically directed against the attacker? The alarm signals salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) are major regulators of plant defense. Their signaling pathways cross-communicate, providing the plant with a regulatory potential to fine-tune its defense reaction. We discovered that the regulatory protein NPR1 functions as a modulator in cross-talk between SA and JA, thereby helping the plant to "decide" which defensive strategy to follow, depending on the type of attacker encountered, and that this function of NPR1 is conserved among Arabidopsis accessions all over the world, suggesting an importany role for plant survival.