G. Raho et al., TISSUE-SPECIFIC EXPRESSION AND ENVIRONMENTAL-REGULATION OF THE BARLEYHVHSP17 GENE PROMOTER IN TRANSGENIC TOBACCO PLANTS, Journal of Experimental Botany, 47(303), 1996, pp. 1587-1594
The 5' upstream region (- 1700 to + 1) of the barley Hvhsp 17 gene, in
ducible by heat shock in young barley seedlings, was transcriptionally
fused with the beta-glucuronidase (GUS) reporter gene. A 2 kb fragmen
t, carrying the CaMV35S promoter, intron 1 from ADH gene of maize, and
the BAR gene, was excised from plasmid pBARGUS (Fromm et al., 1990) a
nd the dual expression vector pBARHSGUS was created. Plasmid pBARHSGUS
was used to transform tobacco protoplasts via PEG-mediated direct DNA
uptake. Four chosen transgenic tobacco plants containing from 1 to 5
integrated copies of the chimeric GUS gene (confirmed by PCR and South
ern analyses) were further analysed. Histochemical and fluorimetrical
analyses were performed in various plant tissues after thermal inducti
on and other environmental treatments. The results obtained show that
the chimeric pHS/GUS fusion was not only induced by heat treatment, bu
t also regulated by some metal ions, and abscisic acid. Furthermore, b
eta-glucuronidase expression in transgenic tobacco was strictly tissue
-specific, being restricted to the vascular boundles of the xylematic
component in the stem and petioles, and absent in any other tissue, wi
th the exception (in one case), of a faint signal in the inner tissue
of the style. It was therefore demonstrated that the 1700 bp upstream
region of the monocot heat shock gene Hvhsp17 was capable of driving a
heat-inducible tissue-specific expression of the marker GUS gene in a
heterologous dicot plant.