The pine Pschi4 promoter directs wound-induced transcription

Abstract Mechanical wounding stimulates the accumulation of Pschi4 transcripts (encoding a putative extracellular chitinase) in pine trees. To gain insight into the transcriptional regulatory region(s) in this gymnosperm defense gene, the 5′-flanking region of Pschi4 was fused to the uid A reporter gene encoding β-glucuronidase (GUS), and the construct was functionally tested for transient expression in onion and pine cells. As little as 200 bp of the upstream sequence was sufficient to promote activated transcription and nearly maximum levels of transient expression in onion cells. Similar results were obtained in bombarded pine cells, although maximum expression appeared to require the entire 4.5 kb of upstream sequence. Having defined potential regulatory regions in the 5′ flanking region of Pschi4 in transient assays, the pine promoter- uid A fusions were functionally tested in stably transformed tobacco plants. As little as 200 bp of the upstream sequence was sufficient to direct wound-inducible transcription. Furthermore, particle bombardment was sufficient to stimulate transgene expression in the transgenic tobacco, indicating that bombardment per se leads to wound responses in vivo. Taken as a whole, our data demonstrate that a gymnosperm promoter can recruit a wound-regulated signal transduction pathway in angiosperms. This suggests that the downstream components of wound signaling pathways are functionally conserved across broad taxonomic groups.