Transcriptional responses of Arabidopsis thaliana to oil contamination

• The expression of 340 genes was modulated by water soluble fraction of marine fuel.
• The stress leads to a fast initial (2 h) transcriptome response.
• HSP genes were up-regulated by the stress.
• Iron deficiency genes were down-regulated by the stress.
• WSF-MF380 encompasses a general abiotic stress response.

The growing demand for fossil-based energy sources has increased oil pollution worldwide. Oil pollution is harmful because 75% of its components are polycyclic aromatic hydrocarbons, which are molecules known to present carcinogenic, mutagenic and teratogenic effects. Mangrove areas are commonly affected by petroleum accidents, making these ecosystems particularly sensitive to oil pollution. In order to elucidate the molecular response of a petroleum mixture on plants, the global gene expression analysis of 10-day-old Arabidopsis thaliana exposed to the water soluble fraction of the marine fuel MF380 (WSF-MF380) was evaluated by a 24 h time-course microarray. The microarray results revealed that 340 genes were modulated by WSF-MF380 stress; these genes were distributed in 12 clusters according to their expression profile. Different classes of biological processes were overrepresented, such as the response to heat, hypoxia, oxidative and osmotic stresses. The expression pattern of five transcription factors and 16 possible targets with enriched cis-regulatory elements was further investigated by qPCR at three selected time-points, revealing that the expression of selected target genes are in accordance with the expression profile of their possible regulator. We further demonstrate that WSF-MF380 stress gives rise to a high induction of genes at the initial time-point t2 h, indicating a rapid molecular response in plants. At t2 h, many HSP genes were induced, showing a similar expression profile in WSF-MF380 and heat stresses. In contrast to the initial induction, many iron deficiency genes, such as bHLH38, bHLH39, bHLH100 and bHLH101, were down regulated from t3 h to t24 h, with no GUS activity observed in the roots of pbHLH38:GUS transgenic A. thaliana after 16 h of exposure. Taken together, these analyses demonstrate that WSF-MF380 exposure seems to encompass a general response to abiotic stresses in plants, which could be an evidence of the complex chemical composition of the oil.