Figure 4.

Betaine accelerated degradation of D1 protein in photodamaged PSII under salt stress. PAMCOD cells were exposed to light at 250 μmol photons m⁻² s⁻¹ in the presence of 250 μg mL⁻¹ lincomycin. Thylakoid membranes were isolated from cells that had been harvested at designated times. Proteins in thylakoid membranes were solubilized and separated by SDS-PAGE as described in “Materials and Methods.” After blotting onto a nitrocellulose membrane, the proteins were allowed to react with D1-specific antibodies. A, Western blot of D1 protein. B, Time course of changes in levels of D1 protein during incubation in light at 250 μmol photons m⁻² s⁻¹. ○, Control cells (20 mm NaCl); •, choline-supplemented cells (20 mm NaCl); ▵, control cells (220 mm NaCl); ▴, choline-supplemented cells (220 mm NaCl). Each point and error bar represents the average and sd, respectively, of results from three independent experiments.