Transient gene expression of foreign genes in preheated protoplasts: stimulation of expression of transfected genes lacking heat shock elements

Translocation of NLS-BSA conjugates into nuclei of permeabilized mammalian cells can be supported by protoplast extract. An experimental system for studying plant cytosolic factors involved in nuclear import

An heterologous experimental system, which allows the study of the yet unknown cytosolic factors involved in nuclear import of nuclear localization signal (NLS)-containing proteins in plants, has been established. The ability of plant cell extract to substitute mammalian cytosol and to promote translocation of NLS-containing proteins into nuclei of permeabilized HeLa cells was demonstrated. The results described in the present work show that nuclear import of fluorescently labeled BSA conjugates bearing the NLS sequence of SV40 large T antigen could be supported by petunia cell cytoplasmic extract. This heterologous system shows the characteristic features of the homologous mammalian system, namely, is ATP dependent and is inhibited by WGA, GTPgammaS as well as by non-fluorescent NLS-BSA conjugates. The system described here offers an experimental method to study and characterise cytosolic factors which are required for nuclear import in plants.

Expression of a borage desaturase cDNA containing an N-terminal cytochrome b5 domain results in the accumulation of high levels of delta6-desaturated fatty acids in transgenic tobacco

gamma-Linolenic acid (GLA; C18:3 delta(6,9,12)) is a component of the seed oils of evening primrose (Oenothera spp.), borage (Borago officinalis L.), and some other plants. It is widely used as a dietary supplement and for treatment of various medical conditions. GLA is synthesized by a delta6-fatty acid desaturase using linoleic acid (C18:2 delta(9,12)) as a substrate. To enable the production of GLA in conventional oilseeds, we have isolated a cDNA encoding the delta6-fatty acid desaturase from developing seeds of borage and confirmed its function by expression in transgenic tobacco plants. Analysis of leaf lipids from a transformed plant demonstrated the accumulation of GLA and octadecatetraenoic acid (C18:4 delta(6,9,12,15)) to levels of 13.2% and 9.6% of the total fatty acids, respectively. The borage delta6-fatty acid desaturase differs from other desaturase enzymes, characterized from higher plants previously, by the presence of an N-terminal domain related to cytochrome b5.