Effect of triadimefon on lipids, sterols, and membrane fluidity in submerged cultures of claviceps purpurea

Abstract

Triadimefon (TDF) (5 mg · liter−1) stimulated the functions of chanoclavine cyclase in submerged cultures of high producing mutant Claviceps purpurea 59 with partially blocked oxidation and cyclization of chanoclavine. The culture growth decreased and specific clavine production was raised. The effect of TDF on growth and production was reversed by plant oil (7.2 g · liter−1), but not by ergosterol (10 mg · liter−1). The oil stimulated growth and lowered both specific alkaloid production and chanoclavin cyclase function. Ergosterol showed the opposite effects. TDF reduced the total mycelial lipids to 66%, sterols to 40%, and phospholipids to 72%. In the cultures supplemented with ergosterol, the sterol content increased 16-fold and phospholipids were lowered to 27%; however, the total lipid content remained unchanged. Oil increased all lipid components. The sterol content was indirectly proportional to the PCPE ratio in all cultures. The membrane fluidity of protoplasts from TDF-treated cultures was higher, in ergosterol-treated cultures lower, and unchanged in the presence of oil. The content of methylated sterols in the TDF-treated cultures was only 2% higher than in controls. The demethylation of sterols in Claviceps occurs first in position C-14, then in C-4. The chanoclavine cyclase function probably does not depend on membrane fluidity, but a correlation between higher activity and low phospholipid content was found.