I. Beck et al., TRANSIENT EXPRESSION ACTIVITY OF RBCS PROMOTER REGIONS FROM BRASSICA-NAPUS IN MESOPHYLL PROTOPLASTS FROM NICOTIANA-TABACUM, Botanica acta, 108(4), 1995, pp. 327-333
The 5' upstream DNA of RbcS genes from Brassica napus contains sequenc
e elements that specifically interact with DNA-binding proteins of the
transcription apparatus in vitro. To clarify if these sequences are f
unctional in vivo, we have studied them in transient expression experi
ments. Fragments generated by successive deletions of the 5' upstream
regions of two RbcS genes were fused in frame to the beta-glucuronidas
e (gusA) reporter gene and GUS activity was monitored fluorometrically
after polyethylene glycol (PEG)-mediated DNA uptake in mesophyll prot
oplasts from Nicotiana tabacum SR1. The results indicate modular organ
ization of cis-elements that together account for full promoter activi
ty. Whereas the TATA-box region alone resulted in basal expression lev
els, enhanced GUS activity was observed in the presence of additional
further-upstream sequences, including the G-box and the G(s)-box. For
maximal activity, the presence of a region containing the I-box was re
quired. In addition to these putative activating DNA regions, evidence
was obtained for regions that negatively affected GUS activity and he
nce may contain silencer element(s).