FIG. 5.

Heat shock response in ΔrpoD mutants. Crude extracts were prepared from wild-type Synechococcus cells (WT) and from the rpoD1 (lanes 1), rpoD2 (lanes 2), rpoD3 (lanes 3), and rpoD4 (lanes 4) mutants, which encode each of four principal type sigma factors, both before (NH) and after (H) heat shock at 45°C for 60 min, and subjected to Western blotting. Note that RpoD1 is an essential sigma factor, and the ΔrpoD1 mutant, in which the rpoD1 gene is partially deleted at its N terminus, has residual RpoD1 activity.