B. Livne et al., TMV-INDUCED EXPRESSION OF TOBACCO BETA-GLUCANASE PROMOTER ACTIVITY ISMEDIATED BY A SINGLE, INVERTED, GCC MOTIF, PLANT SCI, 130(2), 1997, pp. 159-169
Tobacco basic beta-1,3-glucanase has been implicated in plant developm
ent and defense responses against pathogens. We examined the functiona
l cis-elements involved in the response of basic beta-1,3-glucanase pr
omoter (gglb50) to infection with tobacco mosaic virus (TMV). In plant
s transformed with chimeric gglb50-beta-glucuronidase (GUS) reporter g
ene, significant GUS-activity levels were measured in the leaves and i
n roots. Activity in the leaves was further induced (10-fold) by TMV i
nfection. Maximal virus-induced activity was directed by a promoter re
gion between -1233 to +19 (gglb-1233). A 5' deletion to -1038, which r
emoved two TAAGAGCCGCC motifs (GCC-boxes), reduced virus-induced activ
ity. However, when the gglb-1233 promoter was mutated by base substitu
tions within a third, inverted, GCC-box located between positions -106
and -95, virus-induced promoter activity was abolished. Duplication o
f a small region containing this inverted GCC-box in the context of th
e gglb-1233 promoter resulted in increased virus-induced activity. Gel
retardation assay demonstrated nuclear-factor binding to the inverted
GCC-box. These studies strongly suggest the inverted GCC-box as a reg
ulatory element essential for TMV-induced activity directed by the ggl
b50 promoter. (C) 1997 Elsevier Science Ireland Ltd.