SYSTEMIC AND LOCAL INDUCTION OF AN ARABIDOPSIS THIONIN GENE BY WOUNDING AND PATHOGENS

The Arabidopsis Thi2.1 thionin gene was cloned and sequenced. The prom oter was fused to the uidA gene and stably transformed into Arabidopsi s to study its regulation. GUS expression levels correlated with the s teady-state levels of Thi2.1 mRNA, thus demonstrating that the promote r is sufficient for the regulation of the Thi2.1 gene. The sensitivity of the Thi2.1 gene to methyl jasmonate was found to be developmentall y determined. Systemic and local expression could be induced by woundi ng and inoculation with Fusarium oxysporum f sp. matthiolae. A deletio n analysis of the promoter identified a fragment of 325 bp upstream of the start codon, which appears to contain all the elements necessary for the regulation of the Thi2.1 gene. These results support the view that thionins are defence proteins, and indicate the possibility that resistance of Arabidopsis plants to necrotrophic fungal pathogens is m ediated through the octadecanoid pathway.