The vesicle-inducing protein in plastids 1 (Vipp1) is an essential component for thylakoid biogenesis in cyanobacteria and chloroplasts. Vipp1 proteins share significant structural similarity with their evolutionary ancestor PspA (bacterial phage shock protein A), namely a predominantly α-helical structure, the formation of oligomeric high molecular weight complexes (HMW-Cs) and a tight association with membranes. Here, we elucidated domains of Vipp1 from Arabidopsis thaliana involved in homo-oligomerization as well as association with chloroplast inner envelope membranes. We could show that the 21 N-terminal amino acids of Vipp1, which form the first α-helix of the protein, are essential for assembly of the 2 MDa HMW-C but are not needed for formation of smaller subcomplexes. Interestingly, removal of this domain also interferes with association of the Vipp1 protein to the inner envelope. Fourier transform infrared spectroscopy of recombinant Vipp1 further indicates that Escherichia coli lipids bind tightly enough that they can be co-purified with the protein. This feature also depends on the presence of the first helix, which strongly supports an interaction of lipids with the Vipp1 HMW-C but not with smaller subcomplexes. Therefore, Vipp1 oligomerization appears to be a prerequisite for its membrane association. Our results further highlight structural differences between Vipp1 and PspA, which might be important in regard to their different function in thylakoid biogenesis and bacterial stress response, respectively.

The effects of nitrogen and sulfur limitation on various cellular parameters of the cyanobacterium Synechococcus 6301 were studied by electron microscopy, morphometry and biochemical methods. Nitrate and sulfate starvation for 70 h results in a massive glycogen accumulation in parallel to a loss of soluble protein and chlorophyll. Phycobilisomes disappear prior to the degradation of photosynthetic membranes. For sulfate-starved cells, a formation of “storage granules” (poly-β-hydroxy-butyric acid) is typical which amount up to 10% of the cell volume. The composition of polar lipids is simple: equal parts of C 16:0 and C 16:1 are present under all nutritional conditions; their amount is directly correlated with the total cellular membrane area as deter­mined by morphometry. Nitrate starved cells regenerate almost completely in structure and composition within 9 h after nitrate supplementation. Regeneration of sulfate starved cells is retarded; in spite of significant synthesis of phycocyanin within 9 h the cells still exhibit marked signs of starvation.

Summary Plasmid DNA was encapsulated in liposomes to protect from degradation and to support the incorporation into sperm cells. Transgenic spermatozoa carry the foreign DNA to the target cell when fertilizing the egg. Several plasmid constructs were transferred into rabbits, cattle and chicken. The plasmid apparently can persist when provided with a murine amplification promoting sequence. The transgeneity of sperm cells as well as fetuses or offspring was demonstrated by dot blot, Southern blot analysis and PCR. Expression of the transgene was shown as enzymatic activities of the reporter genes SEAP or β‐galactosidase and by gelelectrophoretic characterization of the expressed gene products. The transfer efficiency and the persistence of the gene constructs is significantly increased due to the use of sperm cells as gene carriers mediated by liposomes and the amplification element. Zusammenfassung Gentransfer mittels Liposomen und Spermien Plasmid‐DNA wurde in Liposomen eingeschlossen, um sie vor enzymatischem Abbau zu schützen und ihre Inkorporation in die Spermienzelle zu ermöglichen. Bei der Befruchtung bringt das Spermium die Fremd‐DNA in die Eizelle. Es wurden verschiedene Genkonstrukte in Kaninchen, Rind und Huhn übertragen. Das Plasmid kann offensichtlich persistieren, wenn es eine murine amplifikationsfördernde Sequenz enthält. Die Transgenität von Spermien, Feten und Nachkommen wurde mit Dot Blot, Southern Blot und PCR nachgewiesen, die Expression der Reportergene SEAP und β‐Galaktosidase gelelektrophoretisch bzw. enzymatisch charakterisiert. Der Einsatz von Spermien und Liposomen zur Genübertragung sowie die Verwendung einer ‘amplification promoting sequence' erhöhen die Transfereffizienz und die Persistenz der Genkonstrukte beträchtlich.