Characterization of cytotoxic proteins from mistletoe (Viscum album L.).

Proteins from a laboratory-made oak mistletoe extract and from the commercial mistletoe preparation Iscador Quercus were cytotoxic for leukemia Molt 4 cells in culture. A 50% growth inhibition was obtained with 0.1 microgram/ml proteins for the mistletoe extract and 0.025 microgram/ml for Iscador. On cation exchange chromatography, cytotoxic proteins from the mistletoe extract were mainly eluted at the same positions as purified lectins, while those of Iscador were eluted at the positions of viscotoxins. The data are discussed in relation to the pharmacological activities of the mistletoe protein complexes described in the literature.

[Expression of recombinant human hemoglobin in plants]. / Expression d'hémoglobine humaine recombinante dans les plantes.

Human utilization of recombinant proteins of therapeutical interest, as hemoglobin, implies that the transgenic host allows a low cost production of the active proteins with minimal risks of pathogen contamination. In this regard, the use of transgenic plants could be of great interest. In particular, the systems based on plants could be one of the most economical transgenic system, compared with the others, because biomass obtention in fields is not expensive.

Effects of mistletoe (Viscum album L.) extracts on cultured tumor cells.

Bacterially fermented mistletoe preparations (BFMP) were tested on rat hepatoma tissue culture (HTC) cells and human leukemia Molt 4 cells. A dose-dependent inhibition of the growth rate of the cells was observed. For both cell lines, cytostatic concentrations, expressed in weight of fresh plant, were 0.5 mg/ml culture medium for oak BFMP and 1 mg/ml for apple tree BFMP. However, the action of the two preparations was markedly different on each cell line. Non-viable HTC cells were not stained by trypan blue while non-viable Molt 4 cells were fully colored by this reagent. A lysis of cellular membranes of HTC cells was observed by electron microscopy. Furthermore, oak BFMP inhibited the growth of virus transformed 3T3-SV40 cells more than that of non-transformed 3T3 cells. In contrast to BFMP, non-fermented extracts and a purified mistletoe lectin showed a greater inhibition of the growth of Molt 4 cells than of HTC cells. Samples withdrawn at different times during fermentation gradually lost their inhibitory effect on the growth of Molt 4 cells while their action on HTC cells increased up to the 4th day of fermentation. These results are discussed in relation to the cytotoxic substances of mistletoe already characterized.

Molecular characterisation of two novel maize LRR receptor-like kinases, which belong to the SERK gene family.

Genes encoding two novel members of the leucine-rich repeat receptor-like kinase (LRR-RLK) superfamily have been isolated from maize (Zea mays L.). These genes have been named ZmSERK1 and ZmSERK2 since features such as a putative leucine zipper (ZIP) and five leucine rich repeats in the extracellular domain, a proline-rich region (SPP) just upstream of the transmembrane domain and a C-terminal extension (C) after the kinase domain identify them as members of the SERK (somatic embryogenesis receptor-like kinase) family. ZmSERK1 and ZmSERK2 are single-copy genes and show 79% identity among each other in their nucleotide sequences. They share a conserved intron/exon structure with other members of the SERK family. In the maize genome, ZmSERK1 maps to position 76.9 on chromosome arm 10L and ZmSERK2 to position 143.5 on chromosome arm 5L, in regions generally not involved in duplications. ZmSERK1 is preferentially expressed in male and female reproductive tissues with strongest expression in microspores. In contrast, ZmSERK2 expression is relatively uniform in all tissues investigated. Both genes are expressed in embryogenic and non-embryogenic callus cultures.