The role of microRNAs and phytohormones in plant immune system

The plant-pathogen interaction is a multifactor process that may lead to resistance or susceptible responses of plant to pathogens. During the arms race between plant and pathogens, various biochemical, molecular and physiological events are triggered in plant cells such as ROS signaling, hormone activation and gene expression reprogramming. In plants, microRNAs (miRNAs) are key post-transcriptional regulators of gene expression and are involved in several cellular processes including response to environmental stress. In recent years, plant pathologists have presented a logical approach of plant immune system as zigzag based model that includes two phases of immunity, PTI and ETI in which miRNA molecules are determinant regulators. Here, we present an overview of miRNA biology, a brief explanation of plant immune systems in zigzag model, the role of phytohormones and miRNAs in plant immunity with a main focus on Arabidopsis-Pseudomonas interactions and finally we discuss our results on miRNA expression in lemon-Xanthomonas interactions.