G. Sessa et al., A GCC ELEMENT AND A G-BOX MOTIF PARTICIPATE IN ETHYLENE-INDUCED EXPRESSION OF THE PRB-1B GENE, Plant molecular biology, 28(1), 1995, pp. 145-153
The PRB-1b gene codes for a basic-type pathogenesis-related protein an
d is activated at the transcriptional level by the plant hormone ethyl
ene. To identify cis-acting DNA elements essential for ethylene induct
ion, deleted and mutant forms of the PRB-1b promoter, fused to the bet
a-glucuronidase (GUS) coding region, were introduced in transgenic tob
acco plants. A 73 bp fragment (X1 region) of the PRB-2b promoter, loca
ted between positions -213 and -141, was sufficient to confer ethylene
responsiveness to the reporter gene. The X1 region contains a TAAGAGC
CGCC motif (GCC-box) well conserved in several ethylene-inducible gene
s. A substitution mutation in this sequence, in the context of a 213 b
p PRB-1b promoter, completely abolished ethylene induction in transgen
ic tobacco, defining this conserved motif as part of a cis-acting elem
ent responsive to ethylene. Three other mutations in the X1 region cau
sed a pronounced decrease in the PRB-1b promoter activity in transgeni
c plants, but did not affect ethylene inducibility. One of them, local
ized in a G-box like motif (CACGTG), disrupted the binding site for a
nuclear factor, as observed in gel-shift analysis. Interestingly, the
mobility of the complex formed on the G-box element was dependent on i
ts phosphorylation state. These results suggest that a cis-acting elem
ent involved in the perception of the ethylene signal resides in a GCC
motif and acts in concert with additional elements in the regulation
of ethylene-induced PRB-1b expression.