Large-scale sequencing of conifer cDNAs and targeted molecular cloning have identified many putative conifer defense genes.
Expression of many of these genes is induced in response to biotic stress and some may be expressed only in a few specialized
tissues or cells. Proven functional genomics approaches to test these genes involve expression of proteins in
Escherichia coli or yeast for biochemical characterization or constitutive over-expression in transformed plants. Plant transformation to test
functions of insect-, wound- or pathogen-induced conifer defense genes would benefit from the use of an inducible expression
system. We describe here the development of a heterologous, wound- and insect-inducible gene expression system for conifers
using the potato proteinase inhibitor II (
pinII)-promoter. Using
pinII::GUS and
pinII::(E)-α-bisabolene synthase expression constructs we demonstrate localized induced gene expression in white spruce seedlings (
Picea glauca). Testing of these constructs in
Arabidopsis thaliana and tobacco illustrates the additional potential of the
pinII-promoter to be used in tests of gene function that involve cell-specific and systemic induction.
Keywords Local and systemic defense - Metabolic engineering - Oleoresin - Plant–insect interactions - Secondary metabolism - Terpenoid synthase
Communicated by L. Peña.