Chloroplast ultrastructure and thylakoid polypeptide composition are affected by different salt concentrations in the halophytic plant Arthrocnemum macrostachyum.

The effect of different external salt concentrations, from 0mM to 1030mM NaCl, on photosynthetic complexes and chloroplast ultrastructure in the halophyte Arthrocnemum macrostachyum was studied. Photosystem II, but not Photosystem I or cytochrome b6/f, was affected by salt treatment. We found that the PsbQ protein was never expressed, whereas the amounts of PsbP and PsbO were influenced by salt in a complex way. Analyses of Photosystem II intrinsic proteins showed an uneven degradation of subunits with a loss of about 50% of centres in the 0mM NaCl treated sample. Also the shape of chloroplasts, as well as the organization of thylakoid membranes were affected by NaCl concentration, with many grana containing few thylakoids at 1030mM NaCl and thicker grana and numerous swollen thylakoids at 0mM NaCl. The PsbQ protein was found to be depleted also in thylakoids from other halophytes.