Transient expression experiments show that the maize GapAl promoter ex
hibits a requirement for sequences contained within intron 1 and surro
unding exon border regions for expression in maize Black Mexican Sweet
cells. Maize GapA1-promoter constructs lacking intron 1 are inactive.
Intron 1 and its exon border sequences, when reintroduced into constr
ucts lacking introns, restore gene activity whereas intron 2 and its e
xon borders to not. The minimal promoter so defined encompasses roughl
y 250 bp upstream of the in vivo transcription start and appears also
to include intron 1. An octameric sequence was identified in intron 1
of maize GapA1 which is similar to sequence motifs found in other maiz
e introns known to increase transient expression. Partial restoration
of gene expression in GapA1 constructs lacking intron 1 was achieved t
hrough insertion of the identified octameric sequence.