Transcript profile of chitosan-treated Arabidopsis seedlings

We treated Arabidopsis seedlings with chitosan and carried out a transcript profiling analysis (GeneChip microarrays) in order to identify genes and transcription factors regulated by chitosan. The results showed that jasmonate and defense responsive genes, camalexin and lignin biosynthetic genes were among genes up-regulated by chitosan. Several transcription factors are also strongly induced by chitosan. The results suggested that chitosan can be used as a strong elicitor of defense pathways. Arabidopsis thaliana, ecotype Columbia (Col-0) seeds were sterilized for 7 min in 1.7% (v/v) bleach solution, incubated over night in 4% PPM (Plant Preservative Mixture, Plant Cell Technology, Washington DC, USA) in a full strength sterilized Murashige-Skoog (MS) salt solution with gentle shaking. Subsequently, the seeds were rinsed in abundant sterile water and transferred into 2.5 ml liquid growing media (MS half strength solution) with 0.05% PPM in 6-well plates. The plates were incubated in the dark at 4 °C for two days and finally transferred to continuous light (90µm photons/ m-2) with gentle swirling for four days in a plant growth chamber at 22 °C. . Treatments were performed by comparing a control solution containing the solvent used to solubilize chitosan, and a chitosan solution concentrated 150 µg/ml.