Microbial volatile organic compounds (mVCs) are a part of a collection of microbial secondary metabolites with biological effects on all living organisms. mVCs could function as gaseous modulators of plant growth and plant health. In this study, the defense events induced by plant-deleterious mVCs were investigated. E. aerogenes VCs lead to growth inhibition and plant defense responses such as callose deposition, and ROS accumulation in Arabidopsis thaliana. Data from transcriptional analysis suggests that genes involved in the hypoxia response pathway were enriched in the short exposure up-regulated genes, E. aerogenes VCs induced high transactivation of defense, immune, and metabolic processes after long exposure. In addition, the transcript abundance of the genes involved in the synthetic pathways of antimicrobial metabolites camalexin and coumarin was enhanced after the E. aerogenes VCs exposure. MKK1 and MKK3 were identified as the regulators of the camalexin biosynthesis expression and E. aerogenes VCs-induced callose deposition. The transactivation activity of the coumarin biosynthesis pathway was only regulated by MKK3. Collectively, these studies provide molecular insights into immune responses by plant-deleterious mVCs.
