Effect of nuclear mutation in maize on photosynthetic activity and content of chlorophyll-protein complexes.

A number of new nuclear mutants have been isolated from maize by selection for high chlorophyll (Chl) fluorescence. These mutants show reduced rates of photosynthesis and/or are deficient in Chl. Electrophoretic examination of wild type thylakoid membranes revealed five Chl-protein complexes, two containing only Chl a and three containing Chl a and Chl b. A class of nonviable, photosystem I-deficient mutants was found to be lacking one (A-1) of the two Chl a-protein complexes. A second class of nonviable, photosystem I-lacking mutants was found to be missing not only this A-1 complex but also one or more of the three Chl a and b-containing, light-harvesting Chl-protein complexes. Viable mutants were obtained which appeared to have lost just one of the Chl b-containing complexes, whereas a second class of viable mutants was missing all three of the Chl b-complexes. The results confirm that the A-1 band is associated with the P700-Chl a-protein complex characterized previously. The data also indicate the existence of structurally different forms of the light-harvesting Chl a- and b-containing complexes. The results also show a lower molecular weight band (A-2) containing primarily Chl a and which appears to be required for viability.