Differential expression of Arabidopsis defense-related genes in response to sulfur dioxide

Sulfur dioxide (SO2) is one of the most common and harmful air pollutants. To analyze cellular responses to SO2, we investigated the transcript alterations, antioxidant enzyme activities and reactive oxygen species (ROS) levels in Arabidopsis thaliana (Col-0) exposed to SO2. Transcriptional profiling using Affymetrix GeneChip technology identified 494 genes differentially expressed (>= 2-fold change) in plants exposed to 30 mg M-3 SO2 for 72 h, including up-regulation of some defense-related genes encoding antioxidant enzymes and heat shock proteins. Moreover, numerous genes encoding pathogenesis-related proteins and enzymes required for the phenylpropanoid pathway and for cell wall modification were highly activated upon SO2 exposure. We selected eight of the significantly differentially expressed defense-related genes for analysis using semi-quantitative RT-PCR and confirmed that their expression was up-regulated under SO2 stress. In addition, SO2 exposure caused the enhancement of ROS production, and also increased activities of antioxidant enzymes (superoxide dismutase, peroxidase, glutathione peroxidase and glutathione S-transferase) in Arabidopsis plants. Our results indicated that increased ROS may act as a signal to induce defense responses, which provide enhanced defense capacity to protect plants against SO2 and other environmental stress. This is the first transcriptional profiling that identifies novel genes and pathways involved in SO2 stress responses in plant cells. These data will be helpful for better understanding the molecular basis for plant adaptation to SO2 stress. (C) 2011 Elsevier Ltd. All rights reserved.