Comparative Immunological Studies on the CF1-Complex in Mutants of N. tabacum, Exhibiting Different Capacities for Photosynthesis and Photorespiration and Different Chloroplast Structures

Abstract

We have compared by means of rocket immunoelectrophoresis the amount of CF1-complex in N. tabacum mutants with that in the wild type N. tabacum var. John William’s Broadleaf. Some of these mutants differ from the wild type not only by higher photosynthetic and photorespiratory activities but also by their chloroplast structure. The amount of CF1, present was related to the chlorophyll content. However, no correlation between the amount of CF1, present and a higher photosynthetic and photorespiratory activity was found. On the other hand the molar ratio of CF1, to chlorophyll seems to depend in these tobacco mutants on the morphological structure of the chloroplasts. In chloroplasts of green phenotypes, in particular in those of the mutants N. tabacum var. Consolation, var. NC 95 and var. Xanthi with high grana stacking as well as in those of the wild type N. tabacum var. JWB one CF1-complex occurs per 470-770 chlorophyll molecules. Whereas in chloroplasts of the yellow-green phenotypes with relatively more stroma thylakoids the amount of CF1 seems to be increased only by a factor of 3-4. The yellow phenotypes contain on the average 1 CF1-complex per 60 chlorophyll molecules. The CF1-complex in the investigated chlorophyll-deficient tobacco mutants is immunochemically identical to that of the wild type N. tabacum var. John William’s Broadleaf as demonstrated by means of the tandem-crossed immunoelectrophoresis. However, between the CF1-complex of tobacco and that of other higher plants such as spinach Spinacia oleracea, only partial identity is observed. Comparative quantitative determinations have shown that one CF1-complex binds on the average 8-9 CF1-antibodies which shows that the CF1-complex of the ATPase is fully exposed in the thylakoid membrane, offering a large adsorption surface to the antibodies. Furthermore, it appears that in the immediate vicinity of the CF1-complex large amounts of monogalactolipids are located. Thus, we have calculated that in the variegated NC 95 mutant, chloroplasts of the yellow leaf areas, in which only stroma thylakoids occur, exhibiting only photosystem I activity, as well as in chloroplasts of green leaf areas with a normal ratio of grana and intergrana thylakoids, the molar ratio of monogalactolipids to CF1-complex is the same. It looks as if the functionality and activity of the coupling factor of photophosphorylation depended on a certain quantity of monogalactolipid molecules.