Figure 2.
Differential expression of psbA transcripts after moderate UV-B irradiation supplemented to the standard growth light. Synechococcus sp. PCC 7942 wild-type cells grown at 50 μmol of photons per m2 per s were exposed to supplementary UV-B at 0.4 W/m2 for 2 h and then allowed to recover without UV-B for 30 min. Cell samples were taken at the indicated times for RNA isolations. The levels of psbAI, psbAII, and psbAIII mRNA were detected by hybridization with 100-bp DNA probes specific for the unique 5′ untranslated region of each psbA transcript. Representative autoradiograms from one of two replicates are shown. Molecular size markers in kb are indicated on the left.