An Arabidopsis thaliana Thionin Gene Is Inducible via a Signal Transduction Pathway Different from That for Pathogenesis-Related Proteins

Two cDNAs encoding thionin preproteins have been isolated from Arabidopsis thaliana. The corresponding genes have been designated Thi2.1 and Thi2.2. Southern blot analysis suggests that A. thaliana most probably contains single genes for both thionins. Thi2.2 transcripts have a low basal level in seedlings and show circadian variation. Thi2.2 transcripts were also detected in rosette leaves. No potent elicitors have been found for the Thi2.2 gene. Transcripts of the Thi2.1 gene are not detectable in seedlings but are present in rosette leaves and at a very high level in flowers and in siliques. The expression of the Thi2.1 gene is highly inducible in seedlings by pathogens, silver nitrate, and methyl jasmonate, but not by salicylate, indicating that the gene is induced by a signal transduction pathway that is at least partly different from that for the pathogenesis-related proteins.