Mining the genome of Arabidopsis thaliana as a basis for the identification of novel bioactive peptides involved in oxidative stress tolerance

Although evidence accumulates on the role of plant peptides in the response to external conditions, the number of peptide-encoding genes in the genome is still underestimated. In order to identify novel oxidative stress-induced peptides in Arabidopsis thaliana a tiling array analysis (GeneChip® Arabidopsis Tiling 1.0R Arrays ) was performed on mRNA extracted from leaves treated with paraquat (PQ), an reactive oxygen species inducer and water (control), resulting in the identification of 92,844 and 86,272 transcriptionally active regions (TARs), respectively. Normalized log signals were obtained using the Affymetrix Tiling Analysis Software - Version 1.1, Build 2. ON and OFF probes were selected using a treshold, based on positive controls. Next, groups of 4-13 successive ON probes were combined into short TARs and a selection was made of TARs having an average signal intensity at least 2.6-fold higher after PQ treatment compared to the control treatment, resulting in 176 TARS induced by PQ. paraquat treated A. thaliana leaves (2 replicates) vs control (water) treated A. thaliana leaves (2 replicates), (4 samples in total)