The pine Pschi4 promoter directs wound-induced transcription

Mechanical wounding stimulates the accumulation of Pschi4 transcripts (enco ding a putative extracellular chitinase) in pine trees. To gain insight int o the transcriptional regulatory region(s) in this gymnosperm defense gene, the 5'-flanking region of Pschi4 was fused to the uidA reporter gene encod ing beta-glucuronidase (GUS), and the construct was functionally tested for transient expression in onion and pine cells. As little as 200 bp of the u pstream sequence was sufficient to promote activated transcription and near ly maximum levels of transient expression in onion cells. Similar results w ere 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-tridA fusions were functionally tested in stably transf ormed tobacco plants. As little as 200 bp of the upstream sequence was suff icient to direct wound-inducible transcription. Furthermore, particle bomba rdment was sufficient to stimulate transgene expression in the transgenic t obacco, indicating that bombardment per se leads to wound responses in vivo . Taken as a whole, our data demonstrate that a gymnosperm promoter can rec ruit a wound-regulated signal transduction pathway in angiosperms. This sug gests that the downstream components of wound signaling pathways are functi onally conserved across broad taxonomic groups. (C) 1999 Elsevier Science I reland Ltd. All rights reserved.