Dynamics of membrane potential variation and gene expression induced by Spodoptera littoralis, Myzus persicae, and Pseudomonas syringae in Arabidopsis.

Background: Biotic stress induced by various herbivores and pathogens invokes plant responses involving different defense mechanisms. However, we do not know whether different biotic stresses share a common response or which signaling pathways are involved in responses to different biotic stresses. We investigated the common and specific responses of Arabidopsis thaliana to three biotic stress agents: Spodoptera littoralis, Myzus persicae, and the pathogen Pseudomonas syringae.

Methodology/principal Findings: We used electrophysiology to determine the plasma membrane potential (V(m)) and we performed a gene microarray transcriptome analysis on Arabidopsis upon either herbivory or bacterial infection. V(m) depolarization was induced by insect attack; however, the response was much more rapid to S. littoralis (30 min -2 h) than to M. persicae (4-6 h). M. persicae differentially regulated almost 10-fold more genes than by S. littoralis with an opposite regulation. M. persicae modulated genes involved in flavonoid, fatty acid, hormone, drug transport and chitin metabolism. S. littoralis regulated responses to heat, transcription and ion transport. The latest Vm depolarization (16 h) was found for P. syringae. The pathogen regulated responses to salicylate, jasmonate and to microorganisms. Despite this late response, the number of genes differentially regulated by P. syringae was closer to those regulated by S. littoralis than by M. persicae.

Conclusions/significance: Arabidopsis plasma membranes respond with a V(m) depolarization at times depending on the nature of biotic attack which allow setting a time point for comparative genome-wide analysis. A clear relationship between V(m) depolarization and gene expression was found. At V(m) depolarization timing, M. persicae regulates a wider array of Arabidopsis genes with a clear and distinct regulation than S. littoralis. An almost completely opposite regulation was observed between the aphid and the pathogen, with the former suppressing and the latter activating Arabidopsis defense responses.