Development of the cation-induced stacking capacity during the biogenesis of higher plant thylakoids

We studied the capacity of the thylakoid membrane to form grana stacks in the presence of cations, monovalent or divalent, added to N-2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine “low-salt” disorganized plastids during their greening. Grana stacking was monitored by the yield of heavy subchloroplast fractions separated by differential centrifugation after digitonin disruption of plastids (J. H. Argyroudi-Akoyunoglou, 1976, Arch. Biochem. Biophys., 176, 267–274). Primary thylakoids of the agranal protochloroplasts formed in periodic light do not show the cation-induced stacking capacity of the mature green chloroplast thylakoids. Similarly, the cation effect saturates at lower cation concentrations in mature chloroplasts than in plastids of the early stages of greening. The capacity for cation-induced stacking and for saturation of the effect at low cation concentrations appears gradually after exposure to continuous light and parallel to the appearance of chlorophyll b and the polypeptides of the 25,000–30,000 molecular weight range of lipid-free thylakoids, probably derived from the chlorophyll b-rich chlorophyll protein Complex II. The thylakoid peripheral stroma proteins ribulosediphosphate carboxylase and the coupling factor protein are not involved in the cation-induced stacking, since their removal (H. Strotmann, H. Hesse, and K. Edelmann, 1973, Biochim. Biophys. Acta, 314, 202–210) does not affect the thylakoid aggregation.