Small signaling peptides (SSPs) are small molecules generally less than 200 amino acids with a diverse role in many plant physiological processes such as development and stress responses. SSPs belong to two distinct groups; small post-translationally modified peptides or cysteine-rich, based on structural characteristics arising from protein processing and post-translational modifications. To date, there are no studies available in the literature on genome-wide transcriptomic analysis of SSPs involved in pathogen responses in Arabidopsis. To address this, we generated a time-course RNA-seq experiment using host and nonhost bacterial pathogens for infection in Arabidopsis using the flood inoculation method. From the initial analysis, we found 214 differentially expressed SSPs, after inoculation with the host pathogen Pseudomonas syringae pv. tomato DC3000, from a total of 1,998 SSPs identified in Arabidopsis using PlantSSPdb. From this list of 214 transcripts, 36 belong to known gene ontology categories associated with defense. We selected the top induced SSPs in response to pathogen from our list of 214 SSPs for experimental validation. We obtained Arabidopsis T-DNA knockout mutants for some of these pathogen-induced SSPs and tested the disease phenotype of mutants in response to pathogen infection. RNA-seq analyses of Arabidopsis leaves infected with several other host and nonhost pathogens is underway and the results will be presented.