Exogenous isoprene modulates gene expression in unstressed Arabidopsis thaliana plants

Isoprene is a well‐studied volatile hemiterpene that protects plants from abiotic stress through mechanisms that are not fully understood. The antioxidant and membrane stabilizing potential of isoprene are the two most commonly invoked mechanisms. However, isoprene also affects phenylpropanoid metabolism, suggesting an additional role as a signalling molecule. In this study, microarray‐based gene expression profiling reveals transcriptional reprogramming of Arabidopsis thaliana plants fumigated for 24 h with a physiologically relevant concentration of isoprene. Functional enrichment analysis of fumigated plants revealed enhanced heat‐ and light‐stress‐responsive processes in response to isoprene. Isoprene induced a network enriched in ERF and WRKY transcription factors, which may play a role in stress tolerance. The isoprene‐induced up‐regulation of phenylpropanoid biosynthetic genes was specifically confirmed using quantitative reverse transcription polymerase chain reaction. These results support a role for isoprene as a signalling molecule, in addition to its possible roles as an antioxidant and membrane thermoprotectant. Isoprene synthesis and emission from plants is associated with abiotic stress tolerance but the mechanism is not clear. In this work it is shown that a transcription factor network is induced by exposure of Arabidopsis plants to a physiologically relevant concentration of isoprene in air. The pattern of gene expression is not consistent with a role for reactive oxygen species quenching and other recent work showed that bulk membrane effects are unlikely; genetic reprogramming involving a transcription factor network could be a mechanism of abiotic stress tolerance induced by isoprene.