XVI International Botanical Congess

In the mevalonic acid (MVA)-dependent, cytoplasmic isoprenoid pathway the intermediate farnesyl diphosphate (FPP) serves as substrate for membrane sterol biosynthesis, for farnesylation of proteins, and for synthesis of dolichols, cofactors in protein glycosylation. Growth inhibition of tobacco (N. tabacum L.) Bright Yellow-2 (TBY-2) cells by mevinolin, an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), regulating MVA biosynthesis, could only partially be overcome by exogenous farnesol. Thus, we examined in more detail the effect of farnesol alone on TBY-2 cells. 7-d-old cells, highly diluted into new medium, were sensitive to farnesol, with a critical concentration of 25 ?m needed to cause 100% cell death. When less diluted (20 mL added to 80 mL) the cells were less sensitive. Mevinolin stimulated not only apparent HMGR gene expression and activity, but also did, even synergistically, farnesol. It seems plausible that overstimulation of HMGR activity might be implicated in induction of cell death, as measured by different techniques. Our studies demonstrate similarities to the situation in mammalian cell systems, but also fundamental differences.