WOUND-INDUCED AND DEVELOPMENTAL ACTIVATION OF A POPLAR TREE CHITINASEGENE PROMOTER IN TRANSGENIC TOBACCO

Wounding hybrid poplar (Populus trichocarpa x P. deltoides) trees resu lts in the expression of novel wound-inducible (win) mRNAs thought to encode proteins involved in defense against pests and pathogens. Membe rs of the win6 gene family encode acidic multi-domain chitinases, with combined structure and charge characteristics that differ from previo usly described chitinases. Win6 expression has been shown to occur in pooled unwounded leaves of a wounded (on multiple leaves) poplar plant . Here we demonstrate that wounding a single leaf induces win6 express ion locally, in the wounded leaf, and remotely, in specific unwounded leaves with strong vascular connections to the wounded leaf. We also d emonstrate that a win6 promoter-beta-glucuronidase (GUS) gene fusion ( win6-GUS) responds to wounding locally and remotely in transgenic toba cco. These data indicate that the poplar win6 promoter has regulatory elements that are responsive to 'wound signals' in the heterologous ho st. In addition, win6-GUS is developmentally activated in unwounded yo ung leaves and floral tissues of transgenic tobacco. Similar developme ntal expression patterns are found to occur for win6 in poplar trees, demonstrating that a herbaceous plant can serve as a host for woody tr ee transgene analysis and can accurately predict expression patterns i n tree tissues (e.g. flowers) that would be difficult to study in free -living trees.