Alr4641. (A) Northern-blotting hybridization analysis. Total RNA was isolated from Anabaena PCC7120 grown in BG-11 medium without any oxidative stress-causing agent (Un) or with 1 μM methyl viologen (MV), 1 mM H2O2 (H2O2), 0.25 mM t-butyl hydroperoxide (t-Bx), 50 mM NaCl (NaCl), 100 mM sucrose (Suc), resolved (5 μg per lane) on formaldehyde-agarose gels, transferred onto a nylon membrane and probed with the DIG-labeled alr4641 ORF. The ~900-nt transcript is shown by an arrow. Blot on the left panel was exposed to the X-ray film for 30 s whereas the one on the right was exposed for 15 min. (B) Time course of alr4641 expression. The wild-type Anabaena PCC7120 cells were treated with H2O2 (250 μM) and total RNA isolated at time points indicated. Total RNA (1 μg) from each time point was spotted on a nylon membrane and hybridized to the DIG-labeled alr4641 probe. (C) The wild-type Anabaena PCC7120 was treated with different concentrations of MV, H2O2, t-Bx, cumeme hydroperoxide (Cux), NaCl or sucrose as indicated in the figure. Total RNA was isolated after 1 h of stress and was hybridized to the alr4641 probe. Un, RNA from untreated control cells (D) Induction of the Alr4641 protein in Anabaena. Total proteins (20 μg per lane) were isolated from Anabaena cells treated with sucrose (300 mM) or NaCl (150 mM) or MV (2 μM) and probed with the Alr4641 antiserum. The 23 kD Alr4641 protein is shown by an arrow. (E) Total RNA isolated from untreated Anabaena cells (Un) or cells treated with 1 kGy or 3 kGy dose of gamma radiation was hybridized to the alr4641 probe. After exposure to 3 kGy dose of gamma radiation, total proteins were extracted from Anabaena cells and probed with the Alr4641 antiserum.