J. Vicentecarbajosa et al., BARLEY BLZ1 - A BZIP TRANSCRIPTIONAL ACTIVATOR THAT INTERACTS WITH ENDOSPERM-SPECIFIC GENE PROMOTERS, Plant journal, 13(5), 1998, pp. 629-640
A cDNA encoding a bZIP transcription factor was obtained from barley e
ndosperm and used to identify the corresponding gene from a genomic li
brary. The gene, designated Blz1, contained six exons and five introns
, plus a 442 nt-long 5'-untranslated leader sequence, and was located
on chromosome 5H. The Blz1 mRNA was detected early in endosperm develo
pment and was also expressed in roots and leaves. The BLZ1 protein was
a potent transcriptional activator in a yeast system; 85% of its acti
vity was associated with the first 203 amino acid residues at the N-te
rminus, which included two acidic regions. Presumptive involvement of
Blz1 in the regulation of gene expression in endosperm was ascertained
by the DNA-binding properties of BLZ1 in electrophoretic mobility shi
ft assays (EMSA) and by transient expression in barley developing endo
sperms, using, as effecters, Blz1 in both sense and antisense orientat
ions. In the co-bombardment experiments, the P-glucuronidase (GUS) rep
orter gene responded to Blz1 if under the control of the endosperm-spe
cific Itr1 promoter or under a synthetic promoter containing the endos
perm box of gene Hod. Sucrose synthase promoters Ss1 and Ss2 and synth
etic promoters containing mutated sequences of Hor2 were unaffected in
trans by Blz1.