A Novel Negative Fe-Deficiency-Responsive Element and a TGGCA-Type-Like FeRE Control the Expression of FTR1 in Chlamydomonas reinhardtii

Figure 3

Scanning mutagenesis analysis of the FTR1 −291/−236 region. A series of nucleotide substitutions were introduced into the −291/−236 region. The substituted nucleotides are underlined and red letters are the sequence of FtrFeRE1; and FtrFeRE2. The Ars activities (nmol p-nitrophenol × min−1 × 10−6 cells) expressed by the mutated constructs were measured under –Fe (0𝜇M) or +Fe  (18𝜇M) conditions. Black and white circles represent the Ars activities in independent transformants under −Fe or +Fe conditions, respectively. Bars indicated the median values. The number of the transformants tested for the activity is represented by N. The cotransformation frequency of the constructs was determined by PCR with 16 Arg independent transformants tested in each line.