Diversity in steroidogenesis of symbiotic microorganisms from planthoppers.

Ergosta-5,7,24(28)-trien-3β-ol (trienol)6 was isolated from the intracellular symbiotes (symbiotic microorganisms) of the planthoppers,Nilaparvata lugens andLaodelphax striatellus. The steroidogenic end product of the symbiotes was found to depend on the environmental conditions, i.e., although trienol6 was produced under symbiotic conditions, ergosterol4 was formed in aerobic culture. When the normal diet was replaced by a steroiddeficient artificial one, the ratio of 24-methylenecholesterol5 to total insect sterols was significantly increased. The above study offers further corroborating evidence for our assumption that the host insects require 24-methylenecholesterol5 as an alternate source for cholesterol1 under certain environmental conditions. In our previous biotransformation experiments, 24methylenecholesterol5 was shown to be an immediate precursor of cholesterol1. However, the complexity of the insects' vital functions hindered all subsequent attempted transformations into cholesterol1 of sitosterol2, trienol6, and ergosterol4, under injection conditions.