FIG. 2.

Induction of HEMA by light or by the exogenous addition of MgProto and hemin in the dark. (A) Prior to the treatment, cultures were incubated in the dark for 20 h. At time zero, cultures of strain CC-124 were either shifted from dark to light (fluence rate of white light, 50 μmol m⁻² s⁻¹) (DLS) or supplemented with MgProto (final concentration, 16 μM) or hemin (final concentration, 4 μM) in the dark. Samples were taken at the time points indicated. For RNA blot analyses, 10 μg of total RNA was hybridized with the HEMA probe described in the legend to Fig. 1. The constitutively expressed CBLP gene, encoding a Gβ-like protein (56), served as loading control. (B) Kinetics of HEMA transcript accumulation detected in total RNA isolated from cells at 0, 0.25, 0.5, 1, 2, 3, and 4 h after a dark-to-light shift (DLS) or from cells incubated in the dark after the addition of MgProto or hemin. Intensities of the HEMA hybridization signals from three independent experiments were quantified by phosphorimaging and corrected for unequal loading by the respective CBLP signal. Values are given in arbitrary units relative to the continuous dark level (zero time point), which was set to 1. Error bars indicate standard errors of the means.