Farnesol-induced cell death and stimulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in tobacco cv Bright Yellow-2 cells

Growth inhibition of tobacco (Nicotiana tabacum L. cv Bright Yellow-2) cells by mevinolin, a specific inhibitor of 3-hydrox-3-methylglutaryl-coenzyme A reductase (HMGR) could be partially overcome by the addition of farnesol. However, farnesol alone inhibited cell division and growth as measured by determination of fresh weight increase. When 7-d-old tobacco cv bright Yellow 2 cells were diluted 40-fold into fresh culture, the cells exhibited a dose-dependent sensitivity to farnesol, with 25 mu M sufficient to cause 100% cell death, as measured by different staining techniques, cytometry, and monitoring of fragmentation of genomic DNA. Cells were less sensitive to the effects of farnesol when diluted only 4-fold. Farnesol was absorbed by the cells, as examined by [1-H-3]farnesol uptake, with a greater relative enrichment by the more diluted cells. Both mevinolin and farnesol treatments stimulated apparent HMGR activity. The stimulation by farnesol was also reflected in corresponding changes in the steady-state levels of HMGR mRNA and enzyme protein with respect to HMGR gene expression and enzyme protein accumulation.