Mevastatin-induced inhibition of cell growth in avocado suspension cultures and reversal by isoprenoid compounds

Abstract

Cell suspension cultures were established using soft, friable callus derived from nucellar tissue of 
‘Hass’ avocado (Persea americana Mill.) seed from fruit harvested 190 days after full bloom. Cell 
cultures were maintained in liquid medium supplemented with naphthalene acetic acid (NAA), 
isopentenyl adenine (iP) and sucrose and sub-cultured at 14 day intervals. Growth was typically 
sigmoidal with a lag phase of 7 days followed by an exponential phase of approximately 14 days. 
Mevastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR, EC 1.1.1.34) 
was used to probe the contribution of metabolites of the isoprenoid pathway for avocado cell growth. 
Treatment with mevastatin inhibited cell growth and caused loss of cell viability. Inhibition of cell 
growth was transient and at all concentrations of mevastatin tested, recovery was evident within 17 
days. The arrest of cell growth by 1 and 40 µmol/L mevastatin was negated when this inhibitor of 
HMGR was supplied in the presence of either mevalonolactone (MVL) or farnesyl diphosphate (FDP) . 
By comparison, co-treatment of cells supplied 1 µmol/L mevastatin with stigmasterol showed little or 
no response whereas at 40 µmol/L mevastatin, stigmasterol induced partial recovery of cell growth. 
The results indicate a requirement for mevalonic acid (MVA) and cytosolic isoprenoid biosynthesis, in 
particular FDP, for avocado cell growth and support the hypothesis that appearance of the small-fruit 
phenotype in ‘Hass’ is inextricably linked to activity of HMGR.