M. Ni et al., STRENGTH AND TISSUE-SPECIFICITY OF CHIMERIC PROMOTERS DERIVED FROM THE OCTOPINE AND MANNOPINE SYNTHASE GENES, Plant journal, 7(4), 1995, pp. 661-676
To investigate promoter strength and the tissue-specific patterns of e
xpression, chimeric promoters incorporating subdomains of mannopine sy
nthase (mas2') and octopine synthase (ocs) promoter and activator regi
ons were affixed to a beta-glucuronidase reporter gene and the constru
ctions introduced into tobacco plants. Addition of a trimer of the ocs
upstream activating sequence (UAS) to a mas promoter/activator region
resulted in highly elevated levels of GUS activity in all tissues exa
mined. In leaf tissue, this chimeric promoter is approximately 156-fol
d and 26-fold stronger than are the CaMV 35S and the 'enhanced' double
CaMV 35S promoters, respectively. Expression of GUS activity directed
by the mas and ocs promoters/activators is limited to specific cell t
ypes. Addition of the ocs or mas UAS to the mas or ocs promoter/activa
tor regions modulated these expression patterns. The addition of a tri
mer of the ocs UAS to the mas promoter/activator region resulted in a
transcriptional control element that directed GUS expression in most c
ell types. In addition to the strong expression in transgenic tobacco
plants, this novel promoter directed higher levels of GUS expression t
han did the CaMV 35S promoter in transiently transformed tobacco leaf
discs and suspension culture cells, as well as in cassava and cowpea e
xplants. It is proposed that the strong promoter containing a trimer o
f the ocs UAS affixed to the mas promoter/activator will be useful for
the very high level constitutive expression of linked genes in a wide
variety of plant species.