Tobacco leaves were harvested approximately 70 hours after infiltration with Agrobacterium containing the plasmid encoding the respective genes under control of the 35S promoter. Tissue was frozen in liquid nitrogen, protein was extracted as described by [30 ] and assayed as described by [18 (link),17 (link)].
Firefly Luciferase and Renillia luciferase were assayed using the dual luciferase assay reagents (Promega, Madison, USA). After inoculation and a transient incubation of 2–4 days, 2 cm leaf discs were harvested and ground in 500 μl of Passive Lysis Buffer. Five μl of a 1/100 dilution of this crude extract was assayed in 40 μl of Luciferase Assay Buffer, and the chemiluminescence measured. 40 μl of Stop and Glow™ buffer was then added and a second chemiluminescence measurement made. Absolute RLU were measured in a Turner 20/20 luminometer, with a 5 second delay and 15-second measurement. Data was collected as ratio or, for multiple data points (e.g. several leaves of different ages were infiltrated), the regression-gradient and regression-standard-error were used as a measure of relative promoter strength. Ratios are without units as both the light measurement and protein concentrations are identical. Background controls were run with only the promoter-LUC, 35S-REN reporter plasmid (no TF). In some cases, positive controls were run using a TF with known activity.
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