Transgenic analysis of a hybrid poplar wound-inducible promoter reveals developmental patterns of expression similar to that of storage protein genes.

The wound-inducible win3 multigene family from hybrid poplars (Populus trichocarpa x Populus deltoides) encodes proteins with structural similarities with Kunitz-type protease inhibitors (H.D. Bradshaw Jr., J.B. Hollick, T.J. Parsons, H.R.G. Clarke, M.P. Gordon [1990] Plant Mol Biol 14: 51-59), and at least one member, win3.12, is transcribed de novo in the injured and uninjured leaves of wounded trees (J.B. Hollick, M.P. Gordon [1993] Plant Mol Biol 22: 561-572). A previous study demonstrated that 1352 bp of 5' flanking DNA from the win3.12 gene confers local wound-regulated expression of the beta-glucuronidase gene in transgenic tobacco (Nicotiana tabacum cv Xanthi n.c.) (J.B. Hollick, M.P. Gordon [1993] Plant Mol Biol 22: 561-572). We extend this transgenic analysis here by examining the developmental regulation and systemic wound induction conferred by the same transgene construct in tobacco. Biochemical and histochemical surveys of beta-glucuronidase activity are described for four, independent transgenic lines. The observed spatial and temporal expression patterns coincide with dormant storage tissues and with previously described expression patterns for both seed and vegetative storage protein genes. Developmental northern blot analysis of win3 RNA levels in poplar seeds confirms that proper temporal expression of the reporter gene is maintained during tobacco seed maturation. These results demonstrate that a putative Kunitz-type protease inhibitor can be wound inducible in addition to being expressed in developing seeds.