Fluorometric activity analysis in N . benthamiana leaves after transient expression of pINT121 and pCHF3:GFP. (A) The mean GUS or GFP activity from the CaMV 35S promoter of pINT121 or pCHF3:GFP was arbitrarily assigned as 100% and used to standardize the activity of all other constructs. The standard deviation of each construct is shown with error bars. The number of replicates of each sample is indicated in parentheses. PC, positive control, binary vector pINT121 or pCHF3:GFP; NC, negative control, promoter-less vector pBINGUS or pCHF3 vector without the GFP gene. (B) Fluorometric GFP activity analysis in N. benthamiana leaves after transient expression driven by various βC1 promoter constructs. pCHF3:GFP and pCHF3 were used as positive and negative controls, respectively.