Résumé
In our recent published work it has been demonstrated that
AlSAP
, a gene encoding an A20/AN1 zinc-finger protein (stress-associated protein) of the C4 halophyte grass
Aeluropus
littoralis
, is inducible by various abiotic stresses and by hormonal stimuli. To further investigate the regulation of the gene, a 586-bp genomic fragment upstream of the
AlSAP
translated sequence has been isolated, cloned, and designated as the “
Pr
AlSAP
” promoter. Sequence analysis of “
Pr
AlSAP
” revealed the presence of
cis
-regulatory elements which could be required for abiotic stress, abscisic acid (ABA), and salicylic acid (SA) responsiveness and for tissue-specific and vascular expression. The
Pr
AlSAP
promoter was fused to the β-glucuronidase (
gusA
) gene and the resulting construct transferred into tobacco. Histochemical assays of stably transformed tobacco plants showed that
Pr
AlSAP
is active in this heterologous C3 system. While full-length
gusA
transcripts accumulated in whole 15, 30, and 45-day-old plants, GUS histochemical staining was only observed in leaves and stems of 45-day-old, or older, transgenic seedlings. Histological sections prepared at this stage revealed activity localized in leaf veins (phloem and bundle sheath) and stems (phloem and cortex) but not in roots. Furthermore,
gusA
transcripts accumulated in an age-dependent manner with a basipetal pattern in leaf and stem tissues throughout the plant. In flowers, GUS expression was detected in sepals only. The accumulation of
gusA
transcripts was up-regulated by salt, dehydration, ABA, and SA treatment. Altogether, these results show that, when used in a heterologous dicot system,
Pr
AlSAP
is an age-dependent, abiotic-stress-inducible, organ-specific and tissue-specific promoter.