Functional Expression and Differential Regulation of PETF as a Function of Iron Level. Relative transcript abundances of the genes FLDA, PETF and PCY in triplicate iron-limited (light blue bars) and iron-replete cultures (orange bars) of T. oceanica were measured using a RT-qPCR approach with gene-specific primers pairs (Table 2). The normalized ΔC
values is calculated as 22-ΔC
, where 22 is an arbitrary number chosen to provide a comparable positive logarithmic scale for the transcript abundance of the three genes tested, where a high normalized ΔC
represents a high transcript level.